Type.—Holotype, KU 46903, alcoholic female; obtained 16 km. S Cuatro Ciénegas, Coahuila, México, by John M. Legler (and party), September 6, 1958.[529]Range.—Basin of Cuatro Ciénegas, central Coahuila, Mexico (see map,Fig. 22).Diagnosis.—Posterior margin of carapace of some females having fine corrugations, edge often ragged, and no pale outer margin; septal ridges reduced in adult males; over-all dorsal coloration (in preservative) dark, lacking contrasting patterns.Description.—Plastral length of adult male, 9.6 centimeters (KU 46911); of largest female, 18.4 centimeters (KU 46903).Adult male: anterior edge of carapace smooth; septal ridges reduced; pale outer rim, and small, whitish, dots posteriorly on carapace; surface of carapace slightly gritty or sandpapery posteriorly; snout broadened; over-all dorsal coloration dark gray or slate; contrasting pattern on soft parts of body lacking; ventral surface whitish having few blackish marks posteriorly on undersurface of carapace.Females: posterior margin of carapace usually having fine corrugations; edge of carapace posteriorly often ragged; pale rim of carapace absent; mottled and blotched pattern not contrasting on blackish carapace; dorsal surface of soft parts of body dark gray or slate, lacking contrasting pattern; ventral surface of carapace and posterior part of plastron usually having many blackish flecks and markings; tubercles lacking on anterior edge and in center of carapace posteriorly; septal ridges well developed.Medial angle of epiplastron (as observed through overlying skin) bent at angle of approximately 90 degrees. Other osteological characters presumably as inspinifer.Range in length of plastron (cm.) of 11 females (mean follows extremes); 10.8-18.4, 15.0; proportional measurements of 12 specimens (including adult male, mean follows extremes): PL/HW, 4.70-5.43, 4.93; CL/CW, 1.28-1.43, 1.32; CL/PCW, 1.98-2.42, 2.15; HW/SL, 1.22-1.58, 1.37; CL/PL, 1.29-1.44, 1.36; some females (especially KU 46908) have noticeably elongate carapaces.Variation.—Corrugations best developed on two largest females (KU 46903, 46906), even present on ventral surface of carapace posteriorly and on dorsal surface of tail; development of corrugations not ontogenetic phenomenon as posterior margin relatively smooth on KU 46908 (plastral length, 16.0 cm.) but relatively rugose on KU 46909, which is smaller (plastral length, 13.9 cm.); smallest female (KU 46904) and adult male having posterior margin smooth; smallest female having indication of pale outer rim and small whitish dots posteriorly on carapace, and dark, obtusely-angular line, connecting anterior margins of orbits; blackish marks on ventral surface reduced on KU 46904, 46910, 46912, and UI 43510; UI 43510 (plastral length, 16.3 cm.) resemblesT. s. emoryiin having more contrasting mottled pattern on carapace and limbs, indication of pale outer rim on carapace, and dark line connecting anterior margins of orbits; ventral surface of tail and hind limbs often tinged with red.Color notes from life of young female, topotype (KU 53755) are: mottled carapace dark brown, pale areas buff; dorsal surface of head mottled, olive-brown, pale areas buff; iris orange-buff; upper and lower lips yellow-orange; dorsal surface of limbs olive-brown having yellow to buff suffusion and small blackish marks; pale areas on webbing yellow; ventral surface whitish having yellow at margin of carapace, on neck and limbs.Comparisons.—T. atermost closely resemblesT. spinifer(especially the subspeciesemoryi) in having a gritty or "sandpapery" carapace (reduced,[530]tubercles more scattered), whitish dots on posterior third of carapace (small females and adult male) and a dark line connecting anterior margins of orbits (smallest female). Prior to acquiring the characteristic darkened, dorsal ground color, the pattern on the head and limbs seems to be that ofT. s. emoryi.T. aterresemblesT. muticusin having reduced septal ridges in males, a smooth anterior edge of carapace (especially males), and no enlarged prominences on the anterior edge of the carapace or posteriorly in the center of the carapace on large females.T. aterresemblesT. feroxin having an over-all dark coloration dorsally with no contrasting patterns on adults.T. aterprobably is a small species resemblingT. muticusandT. spinifer emoryi. The head is wide inT. ater, resembling that ofT. ferox, and closely approaching that ofT. spinifer emoryiandT. s. guadalupensis.T. aterresemblesT. feroxandT. s. emoryiin having a narrow carapace.T. aterresemblesT. s. emoryi,T. s. guadalupensisandT. s. pallidus, but differs fromT. muticus,T. feroxand the other subspecies ofT. spiniferin having the carapace widest farther posterior than one-half the length of the carapace.T. aterresemblesT. feroxandT. s. emoryiin shortness of snout. The plastron is short inT. aterand most closely resembles that ofT. s. pallidus,T. s. guadalupensis, andT. s. emoryi.Remarks.—T. ateris confined to permanent, clear-water ponds in the basin of Cuatro Ciénegas. The male and 11 females (KU) were taken at the type locality (a pond known locally as Tío Candido); the other female (UI 43510) was taken from a pond approximately seven miles northward (known locally as Anteojo).T. spinifer emoryialso occurs in the basin of Cuatro Ciénegas. Males and females ofemoryiwere collected in the Río Mesquites (Río Salado drainage) that drains the basin; two adult males ofemoryiwere taken from the clear-water ponds—one from the type locality ofater(KU 46907), and the other (KU 53757) from a pond (known locally as El Mojarral) from which noaterwere obtained. This demonstrated sympatry indicates that the two kinds are not conspecific.However, the nature and frequency of occurrence of characters ofT. ater, suggest that it is subspecifically related toT. spinifer—in effect, a darkened race ofT. s. emoryi. The diagnostic characters of fine corrugations on the posterior margin of the carapace and blackish marks on the ventral surface do not occur on every female ofater. Too, the dorsal coloration of living females (dark brown-buff) is paler than that of preserved specimens (dark gray-slate). Furthermore, a hatchling (CNHM 47367) recorded from Cuatro Ciénegas, Anteojo, is not distinguishable fromemoryi.The mention of absence of septal ridges in males ofT. aterin the original description (Webb and Legler, 1960:22) should be amended. The septal ridges in the only known adult male are reduced; a small, whitish ridge is present on the medial surface of each nostril, but is not conspicuous in anterior view. The one adult male ofateris distinguished fromT. s. emoryiprincipally on the over-all dark, dorsal coloration with concomitant loss of pattern, the noticeably broadened snout, and the reduced septal ridges. The last character mentioned possibly is variable inater(and inemoryiin this region) in view of the variation in development of the ridge on four maleemoryifrom the basin: well-developed on KU 53757 (Mojarral) and KU 46907 (Tío Candido); reduced on KU 53752 (Río Mesquites), resembling development inater; and, reduced on right side only on KU 53753 (Río Mesquites).[531]Presumably, the continued erosive action at the headwaters of the Río Salado has permitted the invasion of this drainage into the formerly isolated basin of Cuatro Ciénegas. In the basin, however, I know of no evidence of a direct aquatic contact between the headwater streams and the isolated, clear-water, ponds. Howemoryientered the ponds is unknown. Some of the ponds are tapped by small, man-made, irrigation canals, but, so far as I know, these are not connected to the river. The ponds have permanent water and are often separated by several miles of arid environment. Overland dispersal between waterways is possible in time of flooding. Local residents tell of the infrequent sale of softshells in Cuatro Ciénegas, which hints at their dispersal via the agency of man. The underlying gypsum substrate of the valley has been subjected to considerable erosion; the ponds observed have deep holes, and small caverns and grottos. There are conflicting reports concerning subterranean connections between ponds. Possibly there are underwater connections between some ponds and the headwater streams of the Río Mesquites. Whatever the dispersal route foremoryiinto the ponds has been, it is strange that the same route has not been traversed byater, permitting its occurrence in the Río Mesquites.On the basis of morphological criteria, I suspect thataterandemoryiare genetically compatible. Possibly there is only sporadic entrance ofemoryiinto the ponds inhabited byater, or the accessible dispersal routes foremoryihave been relatively recent and there has been insufficient time for genetic adaptation.T. ateris maintained as a full species because of the occurrence of two distinct males (KU 46907,emoryi, and KU 46911,ater) in the same pond (Tío Candido, the type locality). These two specimens are contrasted in a photograph accompanying the type description (Webb and Legler, 1960: Pl. II). The restricted distribution ofater, and its characteristics suggest a relict population derived from aferox-like ancestor that may be in the process of becoming extinct.There are two specimens in the CNHM recorded from Cuatro Ciénegas. One is a female (CNHM 55661) having a plastral length of 19.0 centimeters, and no specific locality other than Cuatro Ciénegas. I examined this specimen before I knew of the existence ofater, and noted no unusual features; I have not re-examined the specimen. It is considered representative ofemoryi. The second is a hatchling (CNHM 47367) having a plastral length of 3.2 centimeters, recorded from Cuatro Ciénegas, Anteojo. The carapace is dark tan having small whitish dots intermixed with a few indistinct, small, blackish specks posteriorly. The specimen is indistinguishable fromemoryi.Specimens examined.—Total 12, as follows:Coahuila: KU 46903-06, 46908-12, 53755-56, 16 km. S Cuatro Ciénegas; UI 73510, 5.7 mi. W Cuatro Ciénegas.Records in the literature.—Schmidt and Owens (1944:103) recordemoryifrom Cuatro Ciénegas (no museum numbers listed); presumably their reference is to CNHM 55661.
Type.—Holotype, KU 46903, alcoholic female; obtained 16 km. S Cuatro Ciénegas, Coahuila, México, by John M. Legler (and party), September 6, 1958.
[529]
Range.—Basin of Cuatro Ciénegas, central Coahuila, Mexico (see map,Fig. 22).
Diagnosis.—Posterior margin of carapace of some females having fine corrugations, edge often ragged, and no pale outer margin; septal ridges reduced in adult males; over-all dorsal coloration (in preservative) dark, lacking contrasting patterns.
Description.—Plastral length of adult male, 9.6 centimeters (KU 46911); of largest female, 18.4 centimeters (KU 46903).
Adult male: anterior edge of carapace smooth; septal ridges reduced; pale outer rim, and small, whitish, dots posteriorly on carapace; surface of carapace slightly gritty or sandpapery posteriorly; snout broadened; over-all dorsal coloration dark gray or slate; contrasting pattern on soft parts of body lacking; ventral surface whitish having few blackish marks posteriorly on undersurface of carapace.
Females: posterior margin of carapace usually having fine corrugations; edge of carapace posteriorly often ragged; pale rim of carapace absent; mottled and blotched pattern not contrasting on blackish carapace; dorsal surface of soft parts of body dark gray or slate, lacking contrasting pattern; ventral surface of carapace and posterior part of plastron usually having many blackish flecks and markings; tubercles lacking on anterior edge and in center of carapace posteriorly; septal ridges well developed.
Medial angle of epiplastron (as observed through overlying skin) bent at angle of approximately 90 degrees. Other osteological characters presumably as inspinifer.
Range in length of plastron (cm.) of 11 females (mean follows extremes); 10.8-18.4, 15.0; proportional measurements of 12 specimens (including adult male, mean follows extremes): PL/HW, 4.70-5.43, 4.93; CL/CW, 1.28-1.43, 1.32; CL/PCW, 1.98-2.42, 2.15; HW/SL, 1.22-1.58, 1.37; CL/PL, 1.29-1.44, 1.36; some females (especially KU 46908) have noticeably elongate carapaces.
Variation.—Corrugations best developed on two largest females (KU 46903, 46906), even present on ventral surface of carapace posteriorly and on dorsal surface of tail; development of corrugations not ontogenetic phenomenon as posterior margin relatively smooth on KU 46908 (plastral length, 16.0 cm.) but relatively rugose on KU 46909, which is smaller (plastral length, 13.9 cm.); smallest female (KU 46904) and adult male having posterior margin smooth; smallest female having indication of pale outer rim and small whitish dots posteriorly on carapace, and dark, obtusely-angular line, connecting anterior margins of orbits; blackish marks on ventral surface reduced on KU 46904, 46910, 46912, and UI 43510; UI 43510 (plastral length, 16.3 cm.) resemblesT. s. emoryiin having more contrasting mottled pattern on carapace and limbs, indication of pale outer rim on carapace, and dark line connecting anterior margins of orbits; ventral surface of tail and hind limbs often tinged with red.
Color notes from life of young female, topotype (KU 53755) are: mottled carapace dark brown, pale areas buff; dorsal surface of head mottled, olive-brown, pale areas buff; iris orange-buff; upper and lower lips yellow-orange; dorsal surface of limbs olive-brown having yellow to buff suffusion and small blackish marks; pale areas on webbing yellow; ventral surface whitish having yellow at margin of carapace, on neck and limbs.
Comparisons.—T. atermost closely resemblesT. spinifer(especially the subspeciesemoryi) in having a gritty or "sandpapery" carapace (reduced,[530]tubercles more scattered), whitish dots on posterior third of carapace (small females and adult male) and a dark line connecting anterior margins of orbits (smallest female). Prior to acquiring the characteristic darkened, dorsal ground color, the pattern on the head and limbs seems to be that ofT. s. emoryi.
T. aterresemblesT. muticusin having reduced septal ridges in males, a smooth anterior edge of carapace (especially males), and no enlarged prominences on the anterior edge of the carapace or posteriorly in the center of the carapace on large females.T. aterresemblesT. feroxin having an over-all dark coloration dorsally with no contrasting patterns on adults.
T. aterprobably is a small species resemblingT. muticusandT. spinifer emoryi. The head is wide inT. ater, resembling that ofT. ferox, and closely approaching that ofT. spinifer emoryiandT. s. guadalupensis.T. aterresemblesT. feroxandT. s. emoryiin having a narrow carapace.T. aterresemblesT. s. emoryi,T. s. guadalupensisandT. s. pallidus, but differs fromT. muticus,T. feroxand the other subspecies ofT. spiniferin having the carapace widest farther posterior than one-half the length of the carapace.T. aterresemblesT. feroxandT. s. emoryiin shortness of snout. The plastron is short inT. aterand most closely resembles that ofT. s. pallidus,T. s. guadalupensis, andT. s. emoryi.
Remarks.—T. ateris confined to permanent, clear-water ponds in the basin of Cuatro Ciénegas. The male and 11 females (KU) were taken at the type locality (a pond known locally as Tío Candido); the other female (UI 43510) was taken from a pond approximately seven miles northward (known locally as Anteojo).T. spinifer emoryialso occurs in the basin of Cuatro Ciénegas. Males and females ofemoryiwere collected in the Río Mesquites (Río Salado drainage) that drains the basin; two adult males ofemoryiwere taken from the clear-water ponds—one from the type locality ofater(KU 46907), and the other (KU 53757) from a pond (known locally as El Mojarral) from which noaterwere obtained. This demonstrated sympatry indicates that the two kinds are not conspecific.
However, the nature and frequency of occurrence of characters ofT. ater, suggest that it is subspecifically related toT. spinifer—in effect, a darkened race ofT. s. emoryi. The diagnostic characters of fine corrugations on the posterior margin of the carapace and blackish marks on the ventral surface do not occur on every female ofater. Too, the dorsal coloration of living females (dark brown-buff) is paler than that of preserved specimens (dark gray-slate). Furthermore, a hatchling (CNHM 47367) recorded from Cuatro Ciénegas, Anteojo, is not distinguishable fromemoryi.
The mention of absence of septal ridges in males ofT. aterin the original description (Webb and Legler, 1960:22) should be amended. The septal ridges in the only known adult male are reduced; a small, whitish ridge is present on the medial surface of each nostril, but is not conspicuous in anterior view. The one adult male ofateris distinguished fromT. s. emoryiprincipally on the over-all dark, dorsal coloration with concomitant loss of pattern, the noticeably broadened snout, and the reduced septal ridges. The last character mentioned possibly is variable inater(and inemoryiin this region) in view of the variation in development of the ridge on four maleemoryifrom the basin: well-developed on KU 53757 (Mojarral) and KU 46907 (Tío Candido); reduced on KU 53752 (Río Mesquites), resembling development inater; and, reduced on right side only on KU 53753 (Río Mesquites).
[531]
Presumably, the continued erosive action at the headwaters of the Río Salado has permitted the invasion of this drainage into the formerly isolated basin of Cuatro Ciénegas. In the basin, however, I know of no evidence of a direct aquatic contact between the headwater streams and the isolated, clear-water, ponds. Howemoryientered the ponds is unknown. Some of the ponds are tapped by small, man-made, irrigation canals, but, so far as I know, these are not connected to the river. The ponds have permanent water and are often separated by several miles of arid environment. Overland dispersal between waterways is possible in time of flooding. Local residents tell of the infrequent sale of softshells in Cuatro Ciénegas, which hints at their dispersal via the agency of man. The underlying gypsum substrate of the valley has been subjected to considerable erosion; the ponds observed have deep holes, and small caverns and grottos. There are conflicting reports concerning subterranean connections between ponds. Possibly there are underwater connections between some ponds and the headwater streams of the Río Mesquites. Whatever the dispersal route foremoryiinto the ponds has been, it is strange that the same route has not been traversed byater, permitting its occurrence in the Río Mesquites.
On the basis of morphological criteria, I suspect thataterandemoryiare genetically compatible. Possibly there is only sporadic entrance ofemoryiinto the ponds inhabited byater, or the accessible dispersal routes foremoryihave been relatively recent and there has been insufficient time for genetic adaptation.T. ateris maintained as a full species because of the occurrence of two distinct males (KU 46907,emoryi, and KU 46911,ater) in the same pond (Tío Candido, the type locality). These two specimens are contrasted in a photograph accompanying the type description (Webb and Legler, 1960: Pl. II). The restricted distribution ofater, and its characteristics suggest a relict population derived from aferox-like ancestor that may be in the process of becoming extinct.
There are two specimens in the CNHM recorded from Cuatro Ciénegas. One is a female (CNHM 55661) having a plastral length of 19.0 centimeters, and no specific locality other than Cuatro Ciénegas. I examined this specimen before I knew of the existence ofater, and noted no unusual features; I have not re-examined the specimen. It is considered representative ofemoryi. The second is a hatchling (CNHM 47367) having a plastral length of 3.2 centimeters, recorded from Cuatro Ciénegas, Anteojo. The carapace is dark tan having small whitish dots intermixed with a few indistinct, small, blackish specks posteriorly. The specimen is indistinguishable fromemoryi.
Specimens examined.—Total 12, as follows:Coahuila: KU 46903-06, 46908-12, 53755-56, 16 km. S Cuatro Ciénegas; UI 73510, 5.7 mi. W Cuatro Ciénegas.
Records in the literature.—Schmidt and Owens (1944:103) recordemoryifrom Cuatro Ciénegas (no museum numbers listed); presumably their reference is to CNHM 55661.
Trionyx muticusLesueurSmooth Softshell
Range.—United States from extreme western Pennsylvania, southern Minnesota and South Dakota south to the Gulf of Mexico in Alabama, the western end of the panhandle of Florida, and the eastern half of Texas (see map,Fig. 22.)
Fig. 22.Geographic distribution ofTrionyx aterandTrionyx muticus. 1.T. muticus muticus. 2.T. muticus calvatus. 3.T. ater.
Fig. 22.Geographic distribution ofTrionyx aterandTrionyx muticus. 1.T. muticus muticus. 2.T. muticus calvatus. 3.T. ater.
Diagnosis.—Septal ridges absent; anterior edge of carapace smooth, lacking prominences; juvenal pattern of large dusky spots (sometimes ocellate), or small dusky (not black), dots and short lines; side of head usually devoid of markings except for pale, usually uninterrupted, postocular stripe.Size small; head narrow; snout long; ventral surface of supraoccipital spine broad proximally, lacking median ridge; foramen magnum evenly rounded, ovoid; opisthotic-exoccipital spur absent; distal part of opisthotic wing truncate; lateral condyle of articular surface of quadrate tapered posteriorly, smaller than medial articular surface; angle of epiplastron obtuse, approximately 100 degrees; callosity on epiplastron sometimes covering entire surface; bony bridge wide in relation to length.Description.—Septal ridges absent; external characteristics variable (see accounts of subspecies); range in length, in centimeters, of plastron of ten largest specimens of each sex, (mean follows extremes), males, 11.8-14.0,[533]12.3; females, 17.7-21.5, 18.9; ontogenetic variation in PL/HW, mean PL/HW of specimens having plastral lengths 7.0 centimeters or less, 4.16, ranging from 7.1 to 13.0 centimeters, 5.82, and, exceeding 13.0 centimeters, 7.04; little ontogenetic variation in CL/CW, mean CL/CW of specimens having plastral lengths 8.0 centimeters or less, 1.15, and exceeding 8.0 centimeters, 1.16; mean CL/PCW, 1.97; mean HW/SL, 1.22; mean CL/PL, 1.39.Greatest width of skull usually at level of squamosal (79%); foramen magnum ovoid; opisthotic-exoccipital spur usually absent (97%); distal part of opisthotic wing truncate, sometimes visible in dorsal view; lateral condyle of articular surface of quadrate tapered posteriorly, smaller than medial articular surface; maxillaries not in contact above premaxillaries; combination of seven neurals, seven pairs of pleurals, and contact of seventh pair of pleurals (38%), or eight neurals, seven pairs of pleurals, and separation of seventh pair of pleurals (41%); angle of epiplastron obtuse, greater than 90 degrees; callosities well-developed, frequently on preplastra and epiplastron of adults.Comparisons.—The absence of septal ridges distinguishesmuticusfromferox, all subspecies ofspinifer, andater(ridges are reduced in males ofater). The smooth anterior edge of the carapace distinguishesmuticusfrom all other American kinds exceptaterand some individuals ofT. s. emoryi.T. muticusresembles onlyaterandferoxin usually lacking a well-defined, contrasting pattern of blackish marks on the dorsal surface of the limbs.T. muticusresemblesferoxand differs fromspiniferandaterin lacking a gritty or "sandpapery" carapace on adult males. Adult males ofT. muticus calvatusand some individuals ofT. m. muticusfrom the Colorado River in Texas further resembleferoxin having postocular stripes with thick black borders.T. muticusis the smallest species in North America; the maximum size of the plastron in adult males is approximately 14.0 centimeters (16.0 cm. inspinifer) and of adult females 21.5 centimeters (31.0 cm. inspinifer). Males and females ofmuticusare sexually mature at approximately the same size as someT. s. emoryi; also, the great development of the plastral callosities inmuticuscorresponds to that in someemoryi. The head is narrower inmuticusthan inferoxorspinifer. The carapaces of specimens ofmuticusexceeding plastral lengths of 8.0 centimeters are wider than those offerox,ater,T. s. emoryiandT. s. guadalupensisof corresponding size.T. muticusdiffers fromaterand three subspecies ofspinifer(pallidus,guadalupensis,emoryi) in having the carapace widest at a plane approximately one-half the length of the carapace. The snout is longer inmuticusthan inferoxandspinifer.T. muticusdiffers fromferoxbut resemblesspiniferin having a relatively short plastron.The skulls ofmuticusdiffer from those offeroxbut resemble those ofspiniferin usually having the skull widest at the level of the squamosals. Skulls ofmuticusresemble those offeroxbut differ from those ofspiniferin usually lacking a well-developed opisthotic-exoccipital spur. Skulls ofmuticusare different from those offeroxandspiniferin having the 1) ventral surface of the supraoccipital spine widest proximally, lacking a medial ridge, 2) foramen magnum ovoid, 3) distal part of opisthotic wing truncate, 4) lateral condyle of articular surface of quadrate tapered posteriorly, smaller than medial articular surface, and 5) maxillaries not in contact above premaxillaries.Plastrons ofmuticusdiffer from those ofspiniferandferoxin having an[534]obtusely-angled epiplastron, relatively large callosities in adults, and a wide hyo-hypoplastral bridge (in relation to length).Remarks.—Agassiz (1857:399) regarded Lesueur'sTrionyx muticusas the type species of the genusAmydaand the only species known to belong to the genusAmyda. Stejneger (1944:7, 9, 12) proposed the generic nameEuamydaas a new name for the North AmericanAmyda muticaas understood by Agassiz.Euamydawas proposed for use only if Agassiz's understanding was found to be correct. Actually, Stejneger thought that the Old World and New World kinds concerned were congeneric, and that the type species of the genusAmydawas the Old World speciesAmyda javanicaSchweigger (=Testudo cartilagineaBoddaert).IfTrionyx muticusLesueur is considered to be generically distinct from other soft-shelled turtles,EuamydaStejneger, 1944, is available as a generic name withTrionyx muticusLesueur, 1827, as the type species (by monotypy).Geographical variation.—Trionyx muticusshows no obvious character gradients; the variation is mostly discontinuous and unlike that inT. spinifer. On the basis of differences in the juvenal pattern and pattern on head,T. muticuscan be divided into two subspecies.
Diagnosis.—Septal ridges absent; anterior edge of carapace smooth, lacking prominences; juvenal pattern of large dusky spots (sometimes ocellate), or small dusky (not black), dots and short lines; side of head usually devoid of markings except for pale, usually uninterrupted, postocular stripe.
Size small; head narrow; snout long; ventral surface of supraoccipital spine broad proximally, lacking median ridge; foramen magnum evenly rounded, ovoid; opisthotic-exoccipital spur absent; distal part of opisthotic wing truncate; lateral condyle of articular surface of quadrate tapered posteriorly, smaller than medial articular surface; angle of epiplastron obtuse, approximately 100 degrees; callosity on epiplastron sometimes covering entire surface; bony bridge wide in relation to length.
Description.—Septal ridges absent; external characteristics variable (see accounts of subspecies); range in length, in centimeters, of plastron of ten largest specimens of each sex, (mean follows extremes), males, 11.8-14.0,[533]12.3; females, 17.7-21.5, 18.9; ontogenetic variation in PL/HW, mean PL/HW of specimens having plastral lengths 7.0 centimeters or less, 4.16, ranging from 7.1 to 13.0 centimeters, 5.82, and, exceeding 13.0 centimeters, 7.04; little ontogenetic variation in CL/CW, mean CL/CW of specimens having plastral lengths 8.0 centimeters or less, 1.15, and exceeding 8.0 centimeters, 1.16; mean CL/PCW, 1.97; mean HW/SL, 1.22; mean CL/PL, 1.39.
Greatest width of skull usually at level of squamosal (79%); foramen magnum ovoid; opisthotic-exoccipital spur usually absent (97%); distal part of opisthotic wing truncate, sometimes visible in dorsal view; lateral condyle of articular surface of quadrate tapered posteriorly, smaller than medial articular surface; maxillaries not in contact above premaxillaries; combination of seven neurals, seven pairs of pleurals, and contact of seventh pair of pleurals (38%), or eight neurals, seven pairs of pleurals, and separation of seventh pair of pleurals (41%); angle of epiplastron obtuse, greater than 90 degrees; callosities well-developed, frequently on preplastra and epiplastron of adults.
Comparisons.—The absence of septal ridges distinguishesmuticusfromferox, all subspecies ofspinifer, andater(ridges are reduced in males ofater). The smooth anterior edge of the carapace distinguishesmuticusfrom all other American kinds exceptaterand some individuals ofT. s. emoryi.T. muticusresembles onlyaterandferoxin usually lacking a well-defined, contrasting pattern of blackish marks on the dorsal surface of the limbs.T. muticusresemblesferoxand differs fromspiniferandaterin lacking a gritty or "sandpapery" carapace on adult males. Adult males ofT. muticus calvatusand some individuals ofT. m. muticusfrom the Colorado River in Texas further resembleferoxin having postocular stripes with thick black borders.
T. muticusis the smallest species in North America; the maximum size of the plastron in adult males is approximately 14.0 centimeters (16.0 cm. inspinifer) and of adult females 21.5 centimeters (31.0 cm. inspinifer). Males and females ofmuticusare sexually mature at approximately the same size as someT. s. emoryi; also, the great development of the plastral callosities inmuticuscorresponds to that in someemoryi. The head is narrower inmuticusthan inferoxorspinifer. The carapaces of specimens ofmuticusexceeding plastral lengths of 8.0 centimeters are wider than those offerox,ater,T. s. emoryiandT. s. guadalupensisof corresponding size.T. muticusdiffers fromaterand three subspecies ofspinifer(pallidus,guadalupensis,emoryi) in having the carapace widest at a plane approximately one-half the length of the carapace. The snout is longer inmuticusthan inferoxandspinifer.T. muticusdiffers fromferoxbut resemblesspiniferin having a relatively short plastron.
The skulls ofmuticusdiffer from those offeroxbut resemble those ofspiniferin usually having the skull widest at the level of the squamosals. Skulls ofmuticusresemble those offeroxbut differ from those ofspiniferin usually lacking a well-developed opisthotic-exoccipital spur. Skulls ofmuticusare different from those offeroxandspiniferin having the 1) ventral surface of the supraoccipital spine widest proximally, lacking a medial ridge, 2) foramen magnum ovoid, 3) distal part of opisthotic wing truncate, 4) lateral condyle of articular surface of quadrate tapered posteriorly, smaller than medial articular surface, and 5) maxillaries not in contact above premaxillaries.
Plastrons ofmuticusdiffer from those ofspiniferandferoxin having an[534]obtusely-angled epiplastron, relatively large callosities in adults, and a wide hyo-hypoplastral bridge (in relation to length).
Remarks.—Agassiz (1857:399) regarded Lesueur'sTrionyx muticusas the type species of the genusAmydaand the only species known to belong to the genusAmyda. Stejneger (1944:7, 9, 12) proposed the generic nameEuamydaas a new name for the North AmericanAmyda muticaas understood by Agassiz.Euamydawas proposed for use only if Agassiz's understanding was found to be correct. Actually, Stejneger thought that the Old World and New World kinds concerned were congeneric, and that the type species of the genusAmydawas the Old World speciesAmyda javanicaSchweigger (=Testudo cartilagineaBoddaert).
IfTrionyx muticusLesueur is considered to be generically distinct from other soft-shelled turtles,EuamydaStejneger, 1944, is available as a generic name withTrionyx muticusLesueur, 1827, as the type species (by monotypy).
Geographical variation.—Trionyx muticusshows no obvious character gradients; the variation is mostly discontinuous and unlike that inT. spinifer. On the basis of differences in the juvenal pattern and pattern on head,T. muticuscan be divided into two subspecies.
Trionyx muticus muticusLesueurMidland Smooth Softshell
Plates45,46, and53
Trionyx muticusLesueur, Mém. Mus. Hist. Nat. Paris, 15:263, pl. 7, December, 1827.
Trionyx muticus muticusWebb, Publ. Mus. Nat. Hist. Univ. Kansas, 11:520, August 14, 1959.
Potamochelys? microcephalaGray, Proc. Zool. Soc. London, p. 87, 1864.
Type.—Lectotype, Museum d'Histoire Naturelle, Paris, No. 8813; dried carapace and plastron; obtained from the Wabash River, New Harmony, Posey County, Indiana, by C. A. Lesueur in August, 1827 (Pl. 53).Range.—Central United States; in the Mississippi River drainage from extreme western Pennsylvania, southern Minnesota and South Dakota south to Tennessee, Louisiana and Oklahoma; streams of the Gulf Coast drainage from the Mississippi River in Louisiana westward into Texas including the Colorado River drainage (see map,Fig. 22).Diagnosis.—Juvenal pattern of dusky dots and usually short lines or bacilliform marks; ill-defined pale stripes on snout usually evident just in front of eyes; pale postocular stripe lacking thick, black borders that are approximately one-half width of pale stripe (except some in the Colorado River drainage of Texas).Description.—Plastral length of smallest hatchling, 2.1 centimeters (INHS 3458); of largest male, 14.0 centimeters (CNHM 92003); of largest female, 21.5 centimeters (KU 2308).Juvenal pattern of dusky, grayish marks lacking sharp margins, and usually consisting of both small spots and short streaks or dashes, the former predominating; short streaks or dashes occasionally lacking (TU 14375,Pl. 45, bottom, left; UMMZ 92751); markings variable in number, few and widely spaced, or several and closely approximated (Pl. 45, top, topotypes); pale rim[535]separated from ground color by ill-defined, dusky margin; pattern on adult males well-defined resembling that of hatchlings (TU 16172.1, 16173), scarcely discernable (TU 13294), or absent (TU 1242); mottled and blotched pattern on carapace usually contrasting in large females.Pale stripes extending forward from eyes usually not more than half distance to tip of snout; inner borders of pale stripes on snout usually absent or dusky and indistinct, occasionally blackish (TU 14606); outer borders of pale stripes darker than inner borders, usually blackish; pale stripes on snout occasionally absent (CNHM 7845, UMMZ 92665, TU 5989, none of these specimens being large females); pale postocular stripe having narrow, dusky or blackish borders (especially UMMZ 92751, TU 14436); pale postocular stripe usually complete, occasionally interrupted having prominent dark-bordered anterior segment just behind eye (TU 14416); lower border of postocular stripe usually in contact with dusky postlabial line; no other markings on side of head; pattern on dorsal surface of soft parts of body not contrasting, composed of closely approximated fine markings that are little darker than background, over-all coloration pale grayish; occasionally, few larger and more contrasting markings on hind limbs (UMMZ 92751, TU 14436).Underparts white, usually lacking markings; occasional dusky markings on plastral area (UMMZ 110502), dark spots or flecks on undersurface of carapace (BCB 6043, UMMZ 92666), or markings on throat (UMMZ 95032).Surface of carapace smooth in adult males; large females lacking prominences posteriorly in center of carapace or in nuchal region; anterior edge of carapace smooth in both sexes, but occasionally having regularly spaced furrows or wrinkles (Fig. 8g).Variation.—Short dusky lines and streaks seem to be lacking from the juvenal pattern on the carapace more often in southern populations (Gulf Coast drainage of Texas) than in northern populations (Mississippi River drainage). I have seen one female, KU 48229 (Pl. 46, bottom, left), plastral length 14.5 centimeters that retained a well-defined juvenal pattern, and lacked a mottled and blotched pattern.Color notes from life of 11 turtles, KU 55296-306, (eight adult males, three immature females) from the Kansas River at Lawrence, Douglas County, Kansas, are: Buff-yellow rim of carapace, sometimes having pale orange tinge; dusky, dark brown markings on pale brown or tannish carapace of males; dark and pale brown mottled and blotched pattern on carapace of females (smallest specimens having plastral length, 11.0 cm.), many having orangish or buffy hue; soft parts of body brownish to olive-green dorsally, many having small, blackish marks on hind limbs; webbing of limbs yellowish; pale orange, some yellow, laterally at juncture of dark dorsum and pale ventrum (to a lesser extent on hind limbs); pale orange in some suffusing onto dorsal surface of soft parts of body; black-bordered postocular stripes in males having orangish tinge (pattern somewhat obscured in females); whitish ventral surface in some having pale orangish tinge here and there; many having dusky, grayish flecking on plastral area and anterior ventral surface (most intense on 55306 giving appearance of grayish suffusion).I have seen only three specimens from the Colorado River drainage in Texas. Two of these (UMMZ 92751, TU 14436) are characterized by much black pigmentation. A contrasting pattern of relatively large black marks occurs on the dorsal surface of the soft parts of the body, especially on the[536]hind limbs, and the pale postocular stripes have thick black borders. UMMZ 92751, having a plastral length of 5.5 centimeters, has a juvenal pattern of widely-spaced dark dots that lacks short lines. The othermuticusfrom the Colorado River (CM 3055), a large female 19.0 centimeters in plastral length, has ill-defined postocular stripes lacking dark borders, although a small dusky blotch occurs on the right side of the head.Comparisons.—T. m. muticusdiffers fromT. m. calvatusin having pale stripes on the snout, a juvenal pattern of small dusky spots (usually lacking ocellate spots) and short lines, and a pale postocular stripe lacking thick, blackish borders (except in some turtles from the Colorado River system of Texas). One unique characteristic ofmuticusis the short, dusky lines in the juvenal pattern; these marks, however, are occasionally absent.Remarks.—Trionyx muticusgenerally has been considered a distinct species since its description by Lesueur (1827:263-66, Pl. 7); Wied-Neuwied (1865:53), at least, questioned the identity ofmuticus, believing it to be based on a secondary sexual difference ofT. spiniferus. Lesueur did not designate a type in the description, and mentioned that he had seen only three specimens (op. cit.:264). Stejneger (1944:17-18) discussed two mounted specimens (Nos. 787 and 788) in the Natural History Museum at Paris, and mentioned that No. 787 was designated "… as the type on the printed label (although presumably not done by Lesueur)." Dr. Jean Guibé (in litt.September 24, 1959) informed me that Nos. 787 and 788 are numbers without value and correspond, respectively, to catalog numbers 8813 and 8814. In addition, the Museum possesses an alcoholic specimen, No. 564, obtained by Lesueur from the Wabash River, that seems to have been acquired by the museum after the publication of the original description. No. 8813 is regarded as a lectotype.Gray (1864:87) described the speciesmicrocephalusand questionably included it in the genusPotamochelysFitzinger, 1843; the locality was stated as "Sarawak (Wallace)." Gray especially noted the small elongate head and believed that the acquisition of adult specimens would prove that it belonged to a new genus. Later, Gray (1869:221) proposed the generic nameCalliniaas a new name forAspidonectesas understood by Agassiz (1857:403). Gray referredmicrocephalatoCallinia(op. cit.:214, 222) and recognized alsoAmyda mutica(op. cit.:212). Baur (1888:1121) remarked that "Callinia microcephalaGray, of the British Museum, with the locality Sarawak, isAmyda muticaLes." The speciesmicrocephalushas since been considered a synonym ofTrionyx muticus. Schmidt (1953:110) designated the type locality as New Harmony, Indiana.Müller (1878:641) listed the speciesTrionyx muticusfrom México as follows: "*b. in Alcohol. Mexico. 1872. [2]." Smith and Taylor (1950:18, footnote) wrote that the record required confirmation. Webb and Legler (1960:24) questionably referred this record to the synonomy ofT. ater, which resemblesmuticus.T. muticusis not known to occur in México. According to Dr. Lothar Forcart (in litt.) of the Naturhistorische Museum in Basel, Switzerland, only one specimen on which Müller based his record is extant. My examination of this specimen reveals that it is a hatchlingT. s. emoryi, plastral length 3.5 centimeters, bearing catalog number 1032; there are no additional data of collection.[537]Strecker and Williams (1927:16) mentioned one specimen ofmuticusthat was obtained at Christoval, Tom Green County, Texas, and I presume this is the basis for Pope's mention of this species from Tom Green County, Texas (1949:319). Although I do not doubt thatT. muticusoccurs in Tom Green County, this record possibly is based onT. spiniferbecause, 1) there are no specimens ofmuticusin the Strecker Museum from Tom Green County, but there is one specimen ofspinifer(SM 3282), and in none of Strecker's publications is there any mention ofspiniferfrom Tom Green County, and 2) Strecker had, at least once, misidentified the two species; his record ofmuticusfrom Wallace Bayou, Louisiana (Strecker and Frierson, 1926:last page, no numbers), representsT. spinifer pallidus(SM 2374-75).Specimens examined.—Total 261, as follows:Alabama:County unknown: USNM 118167, Wheeler Reservoir, Tennessee River.Arkansas:Franklin: KU 19459-60, Ozark.Lafayette: KU 2938, 3057, Lewisville.Lawrence: CNHM 92003, Imboden; CNHM 92005, Powhatan; USNM 59214, Black River, Black Rock.Marion: TU 14606 (2), White River at Cotter.Prairie: KU 1831, 1868, 1870, 1874-76, 1930-31, 1957-63, 2294-302, 2305-06, 2308-09, 2838-41, 3002, White River, DeVall's Bluff.Kansas:Barber: USNM 95185-86, 1 mi. S Lake City.Doniphan: KU 1872, 1878, 1964, Doniphan Lake.Douglas: KU 2220, 16148, 23230, 40179, 50825-26, 55296-306, Kansas River, Lawrence; KU 45065-66, 1 mi. N, 1.5 mi. W Lakeview.Ford: KU 51516, Ford.Kearny: KU 48216, 4 mi. S, 1.5 mi. W Deerfield.Marshall: KU 48228, Blue Rapids.Pottawatomie: KU 48229-33, 48238, 2 mi. E Manhattan, Riley County.Reno: USNM 95260, 6 mi. E Turon.Riley: KU 46861, 48234-35, 4 mi. N Manhattan; KU 48236, 2 mi. NE Randolph.Sedgwick: UMMZ 95362, Wichita.Shawnee: UMMZ 95366-67, Topeka.Sumner: USNM 95415, 3 mi. SE Oxford.Washington: KU 48237, 8 mi. S Hanover.Woodson: KU 45064, 1 mi. E, 2 mi. S Neosho Falls.County unknown: USNM 51528.Illinois:Cass: INHS 2146, Beardstown.Coles: INHS 1965-67, 3 mi. S Charleston.Jackson: INHS 5894, 6.5 mi. N Aldridge, Union County; UMMZ 81570, Mississippi River.Jasper: INHS 2412, Rose Hill.Jersey: INHS 2156-58, Grafton.Mason: INHS 2147, Cedar Creek.Mercer: INHS 3458, Keithsburg.Monroe: INHS 4088, 3 mi. NE Columbia.Morgan: CNHM 6028, INHS 2148, Meredosia.Pope: CNHM 2463 (30), Golconda.Schuyler: UI 40-41, Crooked Creek.Shelby: INHS 2283, Holliday.Wabash: INHS 5228, Mt. Carmel.Indiana:Daviess: UMMZ 110234, White River, 1.5 mi. W Elnora.Jefferson: USNM 8337, Madison.Knox: UMMZ 111880-81, "near" Decker Chapel.Posey: INHS 7278-80, 7447, TTC 798, Wabash River, 2-2.5 mi. S New Harmony; UMMZ 110598, 8 mi. NW Mt. Vernon.Iowa:Allamakee: UMMZ 92657,1/4mi. W Victory, Vernon County, Wisconsin; UMMZ 92658-64, Mississippi River, "near" Lansing.Boon: UMMZ 92665, Des Moines River at Ledge State Park.Greene: UMMZ 92666, 3.5 mi. N Scranton.Muscatine: USNM 53521, 54733-34, 54742, 60054-56, Fairport.Louisiana:Beauregard: TU 1242, Sabine River, Merryville.Caddo: CNHM 7845, Gayles.Catahoula: USNM 113228, Jonesville.Concordia: USNM 99870, Red River, "near" Shaw.Ouachita: TU 5989, Monroe.Richland: USNM 100422, Rayville.Sabine: TU 13163, 13294, Sabine River, 8 miles SW Negreet.St. James: TU 7543, Vacherie.St. Mar: USNM 100406, Berwick Bay, "near" Morgan City.Vernon: KU 41380, 46777, Sabine River NW Burr Ferry.Minnesota:Hennepin: AMNH 4761-62, Fort Snelling.Mississippi:Washington:USNM 92605, Greenville.County unknown: USNM 115939.[538]Missouri:Clark: USNM 59267, 59278, Alexandria.Daviess: UMMZ 95505, Grand River, 1 mi. S Jameson.St. Louis: SM 2052, St. Louis.Wayne: UMMZ 82823, St. Francis River.Nebraska:Webster: UMMZ 89526, Republican River, 2 mi. E Inavale.Oklahoma:Cleveland: OU 5480-81, 6473, South Canadian River, 4 mi. SE Norman.Hughes: KU 50845, 4 mi. N Atwood.Kay: OU 9741, 8 mi. E Ponca City.Le Flore: OU 2148; OU 27390, Poteau River below Wister Dam.Love: OU 27472, Hickory Creek, 9 mi. E Marietta.Major: OU 8597, 7 mi. E Orienta.Marshall: KU 50827-29, 50848, 50853, OU 27593-94, TU 16077 (4), Lake Texoma, 2 mi. E Willis.McIntosh: OU 8993, 4 mi. W Onapa.Oklahoma: OU 10137, Lake Oberholser.Payne: UMMZ 89629, Cimarron River, 3 mi. E Ripley; UMMZ 90002, 19 mi. SE Stillwater.Pottawatomie: OU 25176-83, South Canadian River, 5 mi. SW Shawnee.Roger Mills: OU 12472.Sequoyah: OU 9006, Illinois River, 2 mi. NE Gore.Tulsa: UMMZ 95032 (4), Arkansas River at Tulsa.Woodward: CNHM 15472-73; OU 8599-600, 5 mi. E, 1 mi. N Woodward.South Dakota:Yankton: UMMZ 110499-500, Missouri River at Fort Randall; UMMZ 110501-02, Missouri River at Yankton.Tennessee:Benton: UMMZ 53198, Trotter's Landing.Lake: USNM 102677, Reelfoot Lake.Obion: USNM 102910, Reelfoot Lake.Texas:Archer: TU 16173, Lake Diversion.Baylor: TU 16172 (2), Lake Kemp.Brazos: TCWC 7250, Bryan.Clay: TCWC 7248-49, 7259-61, 8 mi. NW Ringgold, Montague County; TU 16667, 3 mi. W Byers.Grayson: UI 2419, Lake Texoma.Gregg: SM 6685, near Gladewater; USNM 22629, Sabine River, 5 mi. S Longview.Liberty: TU 14416, 14375, Trinity River, "near" jct. with Big Creek.McLennan: BCB 6030, 6043, SM 2557, 2561, Lake Waco.Matagorda: CM 3055, Colorado River, Bay City.San Saba: TU 14436, San Saba River, 11 mi. NNW San Saba.Tarrant: UMMZ 92750, Worth Lake, Fort Worth.Wharton: UMMZ 92751, Colorado River, Wharton.No Data: MCZ 1594 (erroneously recorded from Mobile, Alabama); USNM 029261, 59982.Records in the literature.—Arkansas:Garland: Hot Springs (Combs and HurterinStrecker, 1924:47).Jefferson: Pine Bluff.Pulaski: Little Rock.Sebastian: Fort Smith (Hurter and Strecker, 1909:21).Illinois:Adams: Quincy (GarmaninCahn, 1937:179).Alexander: Horseshoe Lake (Cahn,loc. cit.); Cairo (GarmaninCahn,loc. cit.).Carroll: 5 mi. S Savanna (Stejneger, 1944:24).Clay: Louisville.Clinton: Carlyle.Crawford: Robinson (Cahn,loc. cit.).Cumberland: Embarrass River (Peters, 1942:183).Fayette: Vandalia.Gallatin: Shawneetown (Cahn,loc. cit.).Hancock: between Warsaw and Hamilton (Stejneger,op. cit.:23).Jackson: Murphysboro.Jasper: Newton.Marion: Centralia.Mason: Havana.Massac: symbol on map.Menard: Petersburg.Peoria: Peoria.Randolph: Chester (Cahn,loc. cit.).Richland: Olney (Stejneger,loc. cit.).Rock Island: Rock Island.St. Clair: East St. Louis (Cahn,loc. cit.).Union: (Cagle, 1942a:199).White: Carmi.Whiteside: Sterling (Cahn,loc. cit.).Woodford: Mackinaw Creek (GarmaninCahn,loc. cit.).Indiana:Carroll: "near" Delphi (Agassiz, 1857:400).Vigo: Terre Haute (Blatchley, 1891:22).Iowa:Des Moines: "near" Burlington (Agassiz, 1857:400).Dubuque: Mississippi River, 8 mi. S Dubuque (Goldsmith, 1945:447).Lee: Keokuk (Stejneger, 1944:23).Kansas:Barber: 5 mi. SE Lake City; Salt River, S of Aetna (Burt, 1935:321).Cowley: symbols on map (Smith, 1956:157).Gray: Arkansas River, 1 mi. W Cimarron (Clarke, 1956:215).Leavenworth: Missouri River, Fort Leavenworth (Brumwell, 1951:207-08).McPherson: Lindsborg (Breukelman and Smith, 1946:112).Pratt: State Fish Hatchery, "near" Pratt (Taylor, 1933:269).Trego: Wakeeney (Stejneger, 1944:24).Kentucky:Fleming: Fox.Rowan: Triplett (Welter and Carr, 1939:130).County unknown: Ohio River (Funkhouser, 1925:71).[539]Louisiana:De Soto: Bayou Pierre (Strecker and Frierson, 1926:last page, no numbers).Minnesota:Houston: Brownsville (Breckenridge, 1944:183).Winona: Homer (Stejneger, 1944:23).Mississippi:Warren: Vicksburg (Cook, 1946:185).Missouri:Jackson: Fry's Lake (Anderson, 1942:219).Jefferson: Meramec River (Boyer and Heinze, 1934:199).County unknown: Osage River (Agassiz, 1857:400).Nebraska:Franklin:1/2mi. S Franklin; 1 mi. SE Naponee.Furnas: 4 mi. E Cambridge.Lancaster: Lincoln.Nemaha: Peru.Thayer: (Hudson, 1942:102).Thomas: (Smith, 1958:36).New Mexico:San Miguel: Conchos River above Conchos Dam (Shields and Lindeborg, 1956:120).Ohio:Brown: mouth White Oak Creek, Higginsport.Muskingum: "near" Gaysport.Pike: Scioto River in Camp Creek, Newton and Scioto Twps.; Pike Lake.Scioto: Scioto River in Clay and Rush Twps.; Scioto River, Portsmouth; Scioto River, 3 mi. N Rushtown.Tuscarawas: Tuscarawas River, 2 mi. below Gnadenhutten; "near" Winfield.Washington: Dam No. 2, Muskingum River, northern edge of Marietta; Ohio River, 4 mi. SE Marietta (Conant, 1951:156, 264).Oklahoma:Alfalfa: 6.5 mi. NE Ingersoll.Comanche: Camp Boulder, Wichita National Forest (Ortenburger and Freeman, 1930:188).McCurtain:Pushmataha: (Ortenburger, 1927:100).Pennsylvania:Allegheny: Neville Island, Ohio River below Pittsburgh (Atkinson, 1901:154).Clarion: Allegheny River at Foxburg (Netting, 1944:85).?South Dakota:County unknown: Fort Mackenzie, Missouri River, 6-8 mi. below Cedar Island (Stejneger, 1944:15).Tennessee:Lake: Mississippi River (Parker, 1948:29).Pickett: Obey River at Eagle Creek Ford (Shoup, Peyton and Gentry, 1941:75).Wisconsin:Crawford:Pepin: Mississippi River (Breckenridge, 1944:183; Pope and Dickinson, 1928:82).
Type.—Lectotype, Museum d'Histoire Naturelle, Paris, No. 8813; dried carapace and plastron; obtained from the Wabash River, New Harmony, Posey County, Indiana, by C. A. Lesueur in August, 1827 (Pl. 53).
Range.—Central United States; in the Mississippi River drainage from extreme western Pennsylvania, southern Minnesota and South Dakota south to Tennessee, Louisiana and Oklahoma; streams of the Gulf Coast drainage from the Mississippi River in Louisiana westward into Texas including the Colorado River drainage (see map,Fig. 22).
Diagnosis.—Juvenal pattern of dusky dots and usually short lines or bacilliform marks; ill-defined pale stripes on snout usually evident just in front of eyes; pale postocular stripe lacking thick, black borders that are approximately one-half width of pale stripe (except some in the Colorado River drainage of Texas).
Description.—Plastral length of smallest hatchling, 2.1 centimeters (INHS 3458); of largest male, 14.0 centimeters (CNHM 92003); of largest female, 21.5 centimeters (KU 2308).
Juvenal pattern of dusky, grayish marks lacking sharp margins, and usually consisting of both small spots and short streaks or dashes, the former predominating; short streaks or dashes occasionally lacking (TU 14375,Pl. 45, bottom, left; UMMZ 92751); markings variable in number, few and widely spaced, or several and closely approximated (Pl. 45, top, topotypes); pale rim[535]separated from ground color by ill-defined, dusky margin; pattern on adult males well-defined resembling that of hatchlings (TU 16172.1, 16173), scarcely discernable (TU 13294), or absent (TU 1242); mottled and blotched pattern on carapace usually contrasting in large females.
Pale stripes extending forward from eyes usually not more than half distance to tip of snout; inner borders of pale stripes on snout usually absent or dusky and indistinct, occasionally blackish (TU 14606); outer borders of pale stripes darker than inner borders, usually blackish; pale stripes on snout occasionally absent (CNHM 7845, UMMZ 92665, TU 5989, none of these specimens being large females); pale postocular stripe having narrow, dusky or blackish borders (especially UMMZ 92751, TU 14436); pale postocular stripe usually complete, occasionally interrupted having prominent dark-bordered anterior segment just behind eye (TU 14416); lower border of postocular stripe usually in contact with dusky postlabial line; no other markings on side of head; pattern on dorsal surface of soft parts of body not contrasting, composed of closely approximated fine markings that are little darker than background, over-all coloration pale grayish; occasionally, few larger and more contrasting markings on hind limbs (UMMZ 92751, TU 14436).
Underparts white, usually lacking markings; occasional dusky markings on plastral area (UMMZ 110502), dark spots or flecks on undersurface of carapace (BCB 6043, UMMZ 92666), or markings on throat (UMMZ 95032).
Surface of carapace smooth in adult males; large females lacking prominences posteriorly in center of carapace or in nuchal region; anterior edge of carapace smooth in both sexes, but occasionally having regularly spaced furrows or wrinkles (Fig. 8g).
Variation.—Short dusky lines and streaks seem to be lacking from the juvenal pattern on the carapace more often in southern populations (Gulf Coast drainage of Texas) than in northern populations (Mississippi River drainage). I have seen one female, KU 48229 (Pl. 46, bottom, left), plastral length 14.5 centimeters that retained a well-defined juvenal pattern, and lacked a mottled and blotched pattern.
Color notes from life of 11 turtles, KU 55296-306, (eight adult males, three immature females) from the Kansas River at Lawrence, Douglas County, Kansas, are: Buff-yellow rim of carapace, sometimes having pale orange tinge; dusky, dark brown markings on pale brown or tannish carapace of males; dark and pale brown mottled and blotched pattern on carapace of females (smallest specimens having plastral length, 11.0 cm.), many having orangish or buffy hue; soft parts of body brownish to olive-green dorsally, many having small, blackish marks on hind limbs; webbing of limbs yellowish; pale orange, some yellow, laterally at juncture of dark dorsum and pale ventrum (to a lesser extent on hind limbs); pale orange in some suffusing onto dorsal surface of soft parts of body; black-bordered postocular stripes in males having orangish tinge (pattern somewhat obscured in females); whitish ventral surface in some having pale orangish tinge here and there; many having dusky, grayish flecking on plastral area and anterior ventral surface (most intense on 55306 giving appearance of grayish suffusion).
I have seen only three specimens from the Colorado River drainage in Texas. Two of these (UMMZ 92751, TU 14436) are characterized by much black pigmentation. A contrasting pattern of relatively large black marks occurs on the dorsal surface of the soft parts of the body, especially on the[536]hind limbs, and the pale postocular stripes have thick black borders. UMMZ 92751, having a plastral length of 5.5 centimeters, has a juvenal pattern of widely-spaced dark dots that lacks short lines. The othermuticusfrom the Colorado River (CM 3055), a large female 19.0 centimeters in plastral length, has ill-defined postocular stripes lacking dark borders, although a small dusky blotch occurs on the right side of the head.
Comparisons.—T. m. muticusdiffers fromT. m. calvatusin having pale stripes on the snout, a juvenal pattern of small dusky spots (usually lacking ocellate spots) and short lines, and a pale postocular stripe lacking thick, blackish borders (except in some turtles from the Colorado River system of Texas). One unique characteristic ofmuticusis the short, dusky lines in the juvenal pattern; these marks, however, are occasionally absent.
Remarks.—Trionyx muticusgenerally has been considered a distinct species since its description by Lesueur (1827:263-66, Pl. 7); Wied-Neuwied (1865:53), at least, questioned the identity ofmuticus, believing it to be based on a secondary sexual difference ofT. spiniferus. Lesueur did not designate a type in the description, and mentioned that he had seen only three specimens (op. cit.:264). Stejneger (1944:17-18) discussed two mounted specimens (Nos. 787 and 788) in the Natural History Museum at Paris, and mentioned that No. 787 was designated "… as the type on the printed label (although presumably not done by Lesueur)." Dr. Jean Guibé (in litt.September 24, 1959) informed me that Nos. 787 and 788 are numbers without value and correspond, respectively, to catalog numbers 8813 and 8814. In addition, the Museum possesses an alcoholic specimen, No. 564, obtained by Lesueur from the Wabash River, that seems to have been acquired by the museum after the publication of the original description. No. 8813 is regarded as a lectotype.
Gray (1864:87) described the speciesmicrocephalusand questionably included it in the genusPotamochelysFitzinger, 1843; the locality was stated as "Sarawak (Wallace)." Gray especially noted the small elongate head and believed that the acquisition of adult specimens would prove that it belonged to a new genus. Later, Gray (1869:221) proposed the generic nameCalliniaas a new name forAspidonectesas understood by Agassiz (1857:403). Gray referredmicrocephalatoCallinia(op. cit.:214, 222) and recognized alsoAmyda mutica(op. cit.:212). Baur (1888:1121) remarked that "Callinia microcephalaGray, of the British Museum, with the locality Sarawak, isAmyda muticaLes." The speciesmicrocephalushas since been considered a synonym ofTrionyx muticus. Schmidt (1953:110) designated the type locality as New Harmony, Indiana.
Müller (1878:641) listed the speciesTrionyx muticusfrom México as follows: "*b. in Alcohol. Mexico. 1872. [2]." Smith and Taylor (1950:18, footnote) wrote that the record required confirmation. Webb and Legler (1960:24) questionably referred this record to the synonomy ofT. ater, which resemblesmuticus.T. muticusis not known to occur in México. According to Dr. Lothar Forcart (in litt.) of the Naturhistorische Museum in Basel, Switzerland, only one specimen on which Müller based his record is extant. My examination of this specimen reveals that it is a hatchlingT. s. emoryi, plastral length 3.5 centimeters, bearing catalog number 1032; there are no additional data of collection.
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Strecker and Williams (1927:16) mentioned one specimen ofmuticusthat was obtained at Christoval, Tom Green County, Texas, and I presume this is the basis for Pope's mention of this species from Tom Green County, Texas (1949:319). Although I do not doubt thatT. muticusoccurs in Tom Green County, this record possibly is based onT. spiniferbecause, 1) there are no specimens ofmuticusin the Strecker Museum from Tom Green County, but there is one specimen ofspinifer(SM 3282), and in none of Strecker's publications is there any mention ofspiniferfrom Tom Green County, and 2) Strecker had, at least once, misidentified the two species; his record ofmuticusfrom Wallace Bayou, Louisiana (Strecker and Frierson, 1926:last page, no numbers), representsT. spinifer pallidus(SM 2374-75).
Specimens examined.—Total 261, as follows:Alabama:County unknown: USNM 118167, Wheeler Reservoir, Tennessee River.
Arkansas:Franklin: KU 19459-60, Ozark.Lafayette: KU 2938, 3057, Lewisville.Lawrence: CNHM 92003, Imboden; CNHM 92005, Powhatan; USNM 59214, Black River, Black Rock.Marion: TU 14606 (2), White River at Cotter.Prairie: KU 1831, 1868, 1870, 1874-76, 1930-31, 1957-63, 2294-302, 2305-06, 2308-09, 2838-41, 3002, White River, DeVall's Bluff.
Kansas:Barber: USNM 95185-86, 1 mi. S Lake City.Doniphan: KU 1872, 1878, 1964, Doniphan Lake.Douglas: KU 2220, 16148, 23230, 40179, 50825-26, 55296-306, Kansas River, Lawrence; KU 45065-66, 1 mi. N, 1.5 mi. W Lakeview.Ford: KU 51516, Ford.Kearny: KU 48216, 4 mi. S, 1.5 mi. W Deerfield.Marshall: KU 48228, Blue Rapids.Pottawatomie: KU 48229-33, 48238, 2 mi. E Manhattan, Riley County.Reno: USNM 95260, 6 mi. E Turon.Riley: KU 46861, 48234-35, 4 mi. N Manhattan; KU 48236, 2 mi. NE Randolph.Sedgwick: UMMZ 95362, Wichita.Shawnee: UMMZ 95366-67, Topeka.Sumner: USNM 95415, 3 mi. SE Oxford.Washington: KU 48237, 8 mi. S Hanover.Woodson: KU 45064, 1 mi. E, 2 mi. S Neosho Falls.County unknown: USNM 51528.
Illinois:Cass: INHS 2146, Beardstown.Coles: INHS 1965-67, 3 mi. S Charleston.Jackson: INHS 5894, 6.5 mi. N Aldridge, Union County; UMMZ 81570, Mississippi River.Jasper: INHS 2412, Rose Hill.Jersey: INHS 2156-58, Grafton.Mason: INHS 2147, Cedar Creek.Mercer: INHS 3458, Keithsburg.Monroe: INHS 4088, 3 mi. NE Columbia.Morgan: CNHM 6028, INHS 2148, Meredosia.Pope: CNHM 2463 (30), Golconda.Schuyler: UI 40-41, Crooked Creek.Shelby: INHS 2283, Holliday.Wabash: INHS 5228, Mt. Carmel.
Indiana:Daviess: UMMZ 110234, White River, 1.5 mi. W Elnora.Jefferson: USNM 8337, Madison.Knox: UMMZ 111880-81, "near" Decker Chapel.Posey: INHS 7278-80, 7447, TTC 798, Wabash River, 2-2.5 mi. S New Harmony; UMMZ 110598, 8 mi. NW Mt. Vernon.
Iowa:Allamakee: UMMZ 92657,1/4mi. W Victory, Vernon County, Wisconsin; UMMZ 92658-64, Mississippi River, "near" Lansing.Boon: UMMZ 92665, Des Moines River at Ledge State Park.Greene: UMMZ 92666, 3.5 mi. N Scranton.Muscatine: USNM 53521, 54733-34, 54742, 60054-56, Fairport.
Louisiana:Beauregard: TU 1242, Sabine River, Merryville.Caddo: CNHM 7845, Gayles.Catahoula: USNM 113228, Jonesville.Concordia: USNM 99870, Red River, "near" Shaw.Ouachita: TU 5989, Monroe.Richland: USNM 100422, Rayville.Sabine: TU 13163, 13294, Sabine River, 8 miles SW Negreet.St. James: TU 7543, Vacherie.St. Mar: USNM 100406, Berwick Bay, "near" Morgan City.Vernon: KU 41380, 46777, Sabine River NW Burr Ferry.
Minnesota:Hennepin: AMNH 4761-62, Fort Snelling.
Mississippi:Washington:USNM 92605, Greenville.County unknown: USNM 115939.
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Missouri:Clark: USNM 59267, 59278, Alexandria.Daviess: UMMZ 95505, Grand River, 1 mi. S Jameson.St. Louis: SM 2052, St. Louis.Wayne: UMMZ 82823, St. Francis River.
Nebraska:Webster: UMMZ 89526, Republican River, 2 mi. E Inavale.
Oklahoma:Cleveland: OU 5480-81, 6473, South Canadian River, 4 mi. SE Norman.Hughes: KU 50845, 4 mi. N Atwood.Kay: OU 9741, 8 mi. E Ponca City.Le Flore: OU 2148; OU 27390, Poteau River below Wister Dam.Love: OU 27472, Hickory Creek, 9 mi. E Marietta.Major: OU 8597, 7 mi. E Orienta.Marshall: KU 50827-29, 50848, 50853, OU 27593-94, TU 16077 (4), Lake Texoma, 2 mi. E Willis.McIntosh: OU 8993, 4 mi. W Onapa.Oklahoma: OU 10137, Lake Oberholser.Payne: UMMZ 89629, Cimarron River, 3 mi. E Ripley; UMMZ 90002, 19 mi. SE Stillwater.Pottawatomie: OU 25176-83, South Canadian River, 5 mi. SW Shawnee.Roger Mills: OU 12472.Sequoyah: OU 9006, Illinois River, 2 mi. NE Gore.Tulsa: UMMZ 95032 (4), Arkansas River at Tulsa.Woodward: CNHM 15472-73; OU 8599-600, 5 mi. E, 1 mi. N Woodward.
South Dakota:Yankton: UMMZ 110499-500, Missouri River at Fort Randall; UMMZ 110501-02, Missouri River at Yankton.
Tennessee:Benton: UMMZ 53198, Trotter's Landing.Lake: USNM 102677, Reelfoot Lake.Obion: USNM 102910, Reelfoot Lake.
Texas:Archer: TU 16173, Lake Diversion.Baylor: TU 16172 (2), Lake Kemp.Brazos: TCWC 7250, Bryan.Clay: TCWC 7248-49, 7259-61, 8 mi. NW Ringgold, Montague County; TU 16667, 3 mi. W Byers.Grayson: UI 2419, Lake Texoma.Gregg: SM 6685, near Gladewater; USNM 22629, Sabine River, 5 mi. S Longview.Liberty: TU 14416, 14375, Trinity River, "near" jct. with Big Creek.McLennan: BCB 6030, 6043, SM 2557, 2561, Lake Waco.Matagorda: CM 3055, Colorado River, Bay City.San Saba: TU 14436, San Saba River, 11 mi. NNW San Saba.Tarrant: UMMZ 92750, Worth Lake, Fort Worth.Wharton: UMMZ 92751, Colorado River, Wharton.
No Data: MCZ 1594 (erroneously recorded from Mobile, Alabama); USNM 029261, 59982.
Records in the literature.—Arkansas:Garland: Hot Springs (Combs and HurterinStrecker, 1924:47).Jefferson: Pine Bluff.Pulaski: Little Rock.Sebastian: Fort Smith (Hurter and Strecker, 1909:21).
Illinois:Adams: Quincy (GarmaninCahn, 1937:179).Alexander: Horseshoe Lake (Cahn,loc. cit.); Cairo (GarmaninCahn,loc. cit.).Carroll: 5 mi. S Savanna (Stejneger, 1944:24).Clay: Louisville.Clinton: Carlyle.Crawford: Robinson (Cahn,loc. cit.).Cumberland: Embarrass River (Peters, 1942:183).Fayette: Vandalia.Gallatin: Shawneetown (Cahn,loc. cit.).Hancock: between Warsaw and Hamilton (Stejneger,op. cit.:23).Jackson: Murphysboro.Jasper: Newton.Marion: Centralia.Mason: Havana.Massac: symbol on map.Menard: Petersburg.Peoria: Peoria.Randolph: Chester (Cahn,loc. cit.).Richland: Olney (Stejneger,loc. cit.).Rock Island: Rock Island.St. Clair: East St. Louis (Cahn,loc. cit.).Union: (Cagle, 1942a:199).White: Carmi.Whiteside: Sterling (Cahn,loc. cit.).Woodford: Mackinaw Creek (GarmaninCahn,loc. cit.).
Indiana:Carroll: "near" Delphi (Agassiz, 1857:400).Vigo: Terre Haute (Blatchley, 1891:22).
Iowa:Des Moines: "near" Burlington (Agassiz, 1857:400).Dubuque: Mississippi River, 8 mi. S Dubuque (Goldsmith, 1945:447).Lee: Keokuk (Stejneger, 1944:23).
Kansas:Barber: 5 mi. SE Lake City; Salt River, S of Aetna (Burt, 1935:321).Cowley: symbols on map (Smith, 1956:157).Gray: Arkansas River, 1 mi. W Cimarron (Clarke, 1956:215).Leavenworth: Missouri River, Fort Leavenworth (Brumwell, 1951:207-08).McPherson: Lindsborg (Breukelman and Smith, 1946:112).Pratt: State Fish Hatchery, "near" Pratt (Taylor, 1933:269).Trego: Wakeeney (Stejneger, 1944:24).
Kentucky:Fleming: Fox.Rowan: Triplett (Welter and Carr, 1939:130).County unknown: Ohio River (Funkhouser, 1925:71).
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Louisiana:De Soto: Bayou Pierre (Strecker and Frierson, 1926:last page, no numbers).
Minnesota:Houston: Brownsville (Breckenridge, 1944:183).Winona: Homer (Stejneger, 1944:23).
Mississippi:Warren: Vicksburg (Cook, 1946:185).
Missouri:Jackson: Fry's Lake (Anderson, 1942:219).Jefferson: Meramec River (Boyer and Heinze, 1934:199).County unknown: Osage River (Agassiz, 1857:400).
Nebraska:Franklin:1/2mi. S Franklin; 1 mi. SE Naponee.Furnas: 4 mi. E Cambridge.Lancaster: Lincoln.Nemaha: Peru.Thayer: (Hudson, 1942:102).Thomas: (Smith, 1958:36).
New Mexico:San Miguel: Conchos River above Conchos Dam (Shields and Lindeborg, 1956:120).
Ohio:Brown: mouth White Oak Creek, Higginsport.Muskingum: "near" Gaysport.Pike: Scioto River in Camp Creek, Newton and Scioto Twps.; Pike Lake.Scioto: Scioto River in Clay and Rush Twps.; Scioto River, Portsmouth; Scioto River, 3 mi. N Rushtown.Tuscarawas: Tuscarawas River, 2 mi. below Gnadenhutten; "near" Winfield.Washington: Dam No. 2, Muskingum River, northern edge of Marietta; Ohio River, 4 mi. SE Marietta (Conant, 1951:156, 264).
Oklahoma:Alfalfa: 6.5 mi. NE Ingersoll.Comanche: Camp Boulder, Wichita National Forest (Ortenburger and Freeman, 1930:188).McCurtain:Pushmataha: (Ortenburger, 1927:100).
Pennsylvania:Allegheny: Neville Island, Ohio River below Pittsburgh (Atkinson, 1901:154).Clarion: Allegheny River at Foxburg (Netting, 1944:85).
?South Dakota:County unknown: Fort Mackenzie, Missouri River, 6-8 mi. below Cedar Island (Stejneger, 1944:15).
Tennessee:Lake: Mississippi River (Parker, 1948:29).Pickett: Obey River at Eagle Creek Ford (Shoup, Peyton and Gentry, 1941:75).
Wisconsin:Crawford:Pepin: Mississippi River (Breckenridge, 1944:183; Pope and Dickinson, 1928:82).
Trionyx muticus calvatusWebbGulf Coast Smooth Softshell
Plate47
Trionyx muticus calvatusWebb, Univ. Kansas Publ. Mus. Nat. Hist., 11:519, 1 fig., 2 pls., August 14, 1959.
Type.—Holotype, UI 31071, hatchling, sex undetermined, alcoholic; obtained from Pearl River, Roses Bluff, 14 miles northeast Jackson, Rankin County, Mississippi, by William F. Childers on August 25, 1952.Range.—Southeastern United States from the Florida Parishes of Louisiana eastward to the western end of the panhandle of Florida; rivers of the Gulf Coast drainage from the Escambia River drainage, Florida, westward to Louisiana and Mississippi including the Pearl River drainage. The eastern extent of geographic range is not known (see map,Fig. 22).Diagnosis.—Juvenal pattern of large circular spots, often ocellate; no stripes on dorsal surface of snout; pattern on dorsal surface of limbs of fine markings, not in contrast with ground color; pale postocular stripes having thick black borders approximately one half width of pale stripe on adult males.Description.—Plastral length of smallest hatchling, 3.0 centimeters (TU 17301); of largest male, 11.8 centimeters (KU 47118); of largest female, 18.0 centimeters (TU 13473).[540]Juvenal pattern of dusky, circular spots, some ocellate, lacking short lines and streaks; number of spots variable; some spots on carapace of hatchlings may have maximum diameter of three millimeters (TU 17301); pale rim of carapace having dusky, ragged, inner border; juvenal pattern on adult males absent or usually evident, at least posteriorly (TU 17306.1).Dorsal surface of snout lacking pale stripes just in front of eyes; pale postocular stripe having thick, black borders on adult males, but narrower, dusky or blackish borders on juveniles and large females; lower border of postocular stripe usually in contact with dusky postlabial line; no other markings on side of head; pattern on dorsal surface of soft parts of body of closely approximated, fine markings that are not in contrast with ground color, over-all coloration grayish; occasionally few larger and more contrasting markings, especially on hind limbs and anteriolateral surface of forelimbs.Underparts whitish, lacking markings, occasional black flecks or dusky marks posteriorly along ventral edge of carapace (TU 17306.3).Surface of carapace smooth in adult males; large females lacking prominences posteriorly in center of carapace or in nuchal region; anterior edge of carapace smooth in both sexes, but occasionally having regularly spaced furrows or wrinkles on hatchlings.Comparisons.—T. m. calvatuscan be distinguished fromT. m. muticusby the absence of pale stripes on the snout just in front of the eyes, in having pale postocular stripes that have thick, black borders on adult males, and in having a juvenal pattern of large, circular spots that are often ocellate and three millimeters in diameter (no short lines).Remarks.—I have not seen specimens ofcalvatusfrom the Tombigbee-Alabama river drainage; presumably Cook's record (1946:185) from Lowndes County, Mississippi, represents this subspecies.It is still not certain thatcalvatusoccurs in streams that drain into Lake Pontchartrain, Louisiana; TU 17236 from the Amite River that lacks a diagnostic character is questionably referred tocalvatus(Webb, 1959:524). As mentioned previouslyT. s. aspershows little evidence of intergradation withT. spiniferin the Mississippi River drainage;asperis present in streams of the Lake Pontchartrain drainage.T. m. calvatuspresumably shows a corresponding relationship withT. m. muticusin the Mississippi River drainage. There are no specimens that indicate intergradation betweencalvatusandmuticus;calvatusis expected in streams that drain into Lake Pontchartrain, Louisiana. Probablycalvatusoccurs eastward in the Apalachicola drainage system.Specimens examined.—Total, 38 as follows:Florida:Escambia: KU 47116, 50852, 50854-55, 50835-36, TU 13473, 16682, 17301, 17302 (2), Escambia River, 2 mi. E, 1 mi. N Century.Louisiana:East Baton Rouge: TU 17236, Amite River, "near" Baton Rouge.Washington: TU 13795, Bogue Chitto River, Enon; TU 17303 (5), TU 17304 (4), Pearl River, "near" Varnado.No data: TU 17305.Mississippi:Lawrence: KU 47117-19, TU 16956, USNM 7655, Pearl River within 4 mi. of Monticello; TU 17306 (4), Pearl River, 9 mi. S Monticello.Marion: USNM 95133-34, Pearl River, Columbia.Perry: MSC uncatalogued (3), 3 mi. SE New Augusta.Rankin: UI 31071, Pearl River, Roses Bluff, 14 mi. NE Jackson.Records in the literature.—Mississippi:Forrest: no data.Jones: Crawford Bridge.Lowndes: Columbus, Lake Park (Cook, 1946:185).
Type.—Holotype, UI 31071, hatchling, sex undetermined, alcoholic; obtained from Pearl River, Roses Bluff, 14 miles northeast Jackson, Rankin County, Mississippi, by William F. Childers on August 25, 1952.
Range.—Southeastern United States from the Florida Parishes of Louisiana eastward to the western end of the panhandle of Florida; rivers of the Gulf Coast drainage from the Escambia River drainage, Florida, westward to Louisiana and Mississippi including the Pearl River drainage. The eastern extent of geographic range is not known (see map,Fig. 22).
Diagnosis.—Juvenal pattern of large circular spots, often ocellate; no stripes on dorsal surface of snout; pattern on dorsal surface of limbs of fine markings, not in contrast with ground color; pale postocular stripes having thick black borders approximately one half width of pale stripe on adult males.
Description.—Plastral length of smallest hatchling, 3.0 centimeters (TU 17301); of largest male, 11.8 centimeters (KU 47118); of largest female, 18.0 centimeters (TU 13473).
[540]
Juvenal pattern of dusky, circular spots, some ocellate, lacking short lines and streaks; number of spots variable; some spots on carapace of hatchlings may have maximum diameter of three millimeters (TU 17301); pale rim of carapace having dusky, ragged, inner border; juvenal pattern on adult males absent or usually evident, at least posteriorly (TU 17306.1).
Dorsal surface of snout lacking pale stripes just in front of eyes; pale postocular stripe having thick, black borders on adult males, but narrower, dusky or blackish borders on juveniles and large females; lower border of postocular stripe usually in contact with dusky postlabial line; no other markings on side of head; pattern on dorsal surface of soft parts of body of closely approximated, fine markings that are not in contrast with ground color, over-all coloration grayish; occasionally few larger and more contrasting markings, especially on hind limbs and anteriolateral surface of forelimbs.
Underparts whitish, lacking markings, occasional black flecks or dusky marks posteriorly along ventral edge of carapace (TU 17306.3).
Surface of carapace smooth in adult males; large females lacking prominences posteriorly in center of carapace or in nuchal region; anterior edge of carapace smooth in both sexes, but occasionally having regularly spaced furrows or wrinkles on hatchlings.
Comparisons.—T. m. calvatuscan be distinguished fromT. m. muticusby the absence of pale stripes on the snout just in front of the eyes, in having pale postocular stripes that have thick, black borders on adult males, and in having a juvenal pattern of large, circular spots that are often ocellate and three millimeters in diameter (no short lines).
Remarks.—I have not seen specimens ofcalvatusfrom the Tombigbee-Alabama river drainage; presumably Cook's record (1946:185) from Lowndes County, Mississippi, represents this subspecies.
It is still not certain thatcalvatusoccurs in streams that drain into Lake Pontchartrain, Louisiana; TU 17236 from the Amite River that lacks a diagnostic character is questionably referred tocalvatus(Webb, 1959:524). As mentioned previouslyT. s. aspershows little evidence of intergradation withT. spiniferin the Mississippi River drainage;asperis present in streams of the Lake Pontchartrain drainage.T. m. calvatuspresumably shows a corresponding relationship withT. m. muticusin the Mississippi River drainage. There are no specimens that indicate intergradation betweencalvatusandmuticus;calvatusis expected in streams that drain into Lake Pontchartrain, Louisiana. Probablycalvatusoccurs eastward in the Apalachicola drainage system.
Specimens examined.—Total, 38 as follows:Florida:Escambia: KU 47116, 50852, 50854-55, 50835-36, TU 13473, 16682, 17301, 17302 (2), Escambia River, 2 mi. E, 1 mi. N Century.
Louisiana:East Baton Rouge: TU 17236, Amite River, "near" Baton Rouge.Washington: TU 13795, Bogue Chitto River, Enon; TU 17303 (5), TU 17304 (4), Pearl River, "near" Varnado.No data: TU 17305.
Mississippi:Lawrence: KU 47117-19, TU 16956, USNM 7655, Pearl River within 4 mi. of Monticello; TU 17306 (4), Pearl River, 9 mi. S Monticello.Marion: USNM 95133-34, Pearl River, Columbia.Perry: MSC uncatalogued (3), 3 mi. SE New Augusta.Rankin: UI 31071, Pearl River, Roses Bluff, 14 mi. NE Jackson.
Records in the literature.—Mississippi:Forrest: no data.Jones: Crawford Bridge.Lowndes: Columbus, Lake Park (Cook, 1946:185).
NATURAL HISTORY
Habitat
Most writers who describe the general habitat of soft-shelled turtles mention large rivers and streams having some current, and large permanent, quiet bodies of water having soft mud or sand bottoms, but note the general avoidance of temporary water. The impermanence of water in the ponds and "charcos" of headwaters of streams may preclude the presence of softshells from these otherwise suitable habitats. Seemingly, soft-shelled turtles are not restricted to particular local situations or microhabitats in a continuous aquatic environment as are some kinds of fish, which seem to be more or less confined to riffle areas or deep holes. Certain activities of softshells such as burying themselves in soft sand in shallow water or seeking crawfish and other food over a gravel-rock substrate or one that is débris-laden, are best carried on in different habitats. Repeated observations of turtles that are probably engaged in a specific activity in a restricted area may lead to erroneous general conclusions regarding the over-all preference for a specific habitat. Perhaps this accounts for Conant's statement (1951:156) that "In the lower portion of the Scioto River [Ohio] it appears that the present species [muticus] is abundant whilespiniferis almost entirely absent."
Cagle (1954:181) wrote that softshells "inhabit the extreme headwaters and smaller tributaries." Other statements in the literature indicate the variety in kinds of habitat. In Louisiana, Beyer (1900:44) mentionedspiniferas abundant "in all inland waters, preferring, however, such bayous which have sloping and sandy banks upon which they are fond of sunning themselves." Viosca (1923:41) reported soft-shelled turtles as characteristic "of the large silt-bearing rivers … such as the Pearl, Amite, Mississippi and Atchafalaya." Cagle and Chaney (1950:386) wrote thatspiniferin Louisiana was found in greatest abundance in streams having some current, but that individuals were also common in quiet areas; the habitats recorded were: False River—a lake of clear water supporting an abundance of submerged vegetation, the shallow ends having mats of water hyacinth; Lakes Iatt and Bistineau—cypress swamps having clear or muddy water; Caddo Lake—a large lake having a light oil film on the surface of the water, and vegetation toward the shore consisting of cattails, water lilies and water hyacinths, and along the bank of cypress and willow trees; Caddo Lake Spillway—muddy with swift current; Sabine River—swift current, traps set in quieter backwater areas or near cypress logs in river; Lacassine Refuge—traps set in inlets and coves of ship channel having vegetation of water hyacinth, alligator grass, and along bank, saw grass, cypress knees and snags. Stejneger (1944:59) reportedspinifertaken in barrow pits in Mississippi.[542]In Southern Illinois, Cagle (1942:160) recordedspiniferin drainage ditches (normally having several feet of water and a lush growth of aquatic vegetation) that connect inland swamps to the Mississippi flood-plain but dry up periodically, and in Elkville Lake, an artificial lake having much aquatic vegetation in shallow areas (op. cit.:157). Myers (1927:339) recorded aspiniferfrom Indiana from a "tiny brook." In east-central Illinois P. W. Smith (1947:39) recordedspiniferin mud-bottomed dredge ditches, lakes, ponds, small streams and rivers, whereasmuticuswas found to prefer rivers having clean, sandy bottoms and was not taken from lakes or small streams. This restriction in habitat preference ofmuticusis again emphasized by Smith and Minton (1957:346) who wrote that in Illinois and Indiana,muticus"generally avoids lakes and minor streams." Weed (1923:48), however, recordedmuticus(andspinifer) from Meredosia Bay, Illinois, presumably a broad, shallow, muddy ox-bow lake of the Illinois River.In Minnesota,spiniferhas been taken from the Mississippi River, which is described as fairly swift having a fluctuating water level, sandy islands, mud banks, a bed of pebbles and large boulders, and abundant crawfish (Breckenridge, 1955:5). In Michigan, Edgren (1942:180) recordedspiniferfrom a "very small muck-bottomed lake." Evans and Roecker (1951:69) recordedspiniferfrom Long Point, Lake Ontario, which is a "broad sand spit, straight on the lakeward side but irregular with wet flats and lagoons on the bayside."In Kansas, Brumwell (1951:207-08) found "mostly young [muticus] … in the old ponds left during flood stages of the Missouri River" … andspiniferoccasionally … "in the backwaters where stagnant ponds had been formed." In southcentral Kansas, Burt (1935:321) reportedmuticusfrom "a sandbar at junction of a small creek and Medicine River" … and … a "shallow sand-bottomed, algae-filled pasture streamlet." The same author reportedspiniferfrom a "sand-bottomed prairie streamlet" … and … "an alga-filled pool near a stream." Burt (loc. cit.) remarked that "No ecological differences in general habitat and field behavior ofmuticaandspiniferare evident in Kansas." Clarke (1958:21) observedspiniferin Long Creek (Osage County, Kansas), which is a winding stream, characterized by numerous deep holes alternating with rocky riffles, and having high and wooded banks, and mostly mud bottom but occasional rock bottom.Marr (1944:490) mentioned aspiniferthat was obtained on the bank of a small, mud-bottomed stream in the Texas panhandle, and Linsdale and Gressitt (1937:222) recordedspiniferfrom irrigation canals in Baja California.In southern Florida,feroxoccurs in all fresh-water habitats (Duellman and Schwartz, 1958:272). Carr (1940:107) reportedferoxas widely distributed in streams, lakes, big springs and canals. Judging from the numbers of turtles, "the larger canals in the Everglades must represent something like an optimum habitat" (Carr, 1952:417). Wright and Funkhouser (1915:119) wrote that in the Okefinokee Swamp,feroxwas especially abundant where the water is deep and the bottom soft, and the species was found wherever there were alligators. Deckert (1918:31) wrote that youngferoxwere taken in springs and brooks near Jacksonville, Florida. Marchand (inCarr, 1952:417-19) observedferoxwhile water-goggling in Florida and noted that individuals buried themselves in deep water in white sand, mud or bubbling mud-sand springs, sometimes where there was vegetation overhead.[543]Neill (1951:16) collectedferoxin marshes, "prairies," flood-plain lakes, lagoons, ox-bow lakes, mangrove swamps, rivers, creeks, calcareous spring runs, man-made lakes and lime sinks. The same author (loc. cit.) reported takingagassizi(=asper) in large muddy rivers, clear "blackwater" streams, calcareous spring runs, creeks, marshes, lagoons, ox-bow lakes, flood-plain lakes, lime sinks, man-made lakes, and smaller ponds. Crenshaw and Hopkins (1955:16), however, stated that in the area whereT. feroxandT. spinifer asperoverlap, "asperis nearly always an inhabitant of fluviatile situations whereasferoxis equally closely confined to non-fluviatile lakes and ponds"; in the region of sympatry, Schwartz (1956:8) reportedferoxfrom "a moderately fast, blackwater stream [Combahee River, South Carolina]."Carr (1952:417) wrote thatferoxis not uncommon near the mouths of streams in brackish waters, where the tide must occasionally take it to sea, and cited Conant, who told of an individual found at sea in Bahaman waters; Carr (1940:25) listedferoxas occasional in the marine-littoral, mangrove swamps, as did Neill (1951:16). Neill (1958:26-27) mentioned his observance offeroxat the mouth of the Pithlachascotee River, Pasco County, Florida, where the water is sufficiently saline to favor the growth of oysters, and added that commercial fishermen had told him that these turtles are sometimes netted with loggerhead sea turtles (Caretta) in the Indian River. Neill (op. cit.:5-6) also noted the presence offeroxon Meritt Island, which supports an extensive saltwater herpetofauna, off the coast of Brevard County, Florida. Löding (1922:47) recordedspiniferfrom Fig Island, Mobile County, Alabama, which is probably a marine or brackish water habitat. Cagle and Chaney (1950:386) obtained onespiniferin a brackish marsh of the Sabine Wildlife Refuge, Louisiana; the poor trapping returns here (oneTrionyxand onePseudemysin 408 trap-hours) suggest that fresh-water species are not abundant in brackish habitats. Neill (1958:26-27) has summarized the occurrence of soft-shelled turtles in marine and brackish habitats.My own observations indicate a variety of habitat preferences; the term "relatively clear" refers to waters in which visibility extends four to six inches below the surface at night using a head-light.Individuals ofspiniferhave been taken in large, deep rivers having a moderate to swift current, relatively clear water, mostly sand and clay bottoms, and emergent débris intermittent along the shoreline; the banks may be steep and of mud having a sparse growth of herbs (Black Warrior River, south of Tuscaloosa, Alabama), or of low extensive, sandy bars and beaches (Escambia River, near Century, Florida,Pl. 50, Fig. 1). A juvenilespiniferwas taken by hand among rocks in quiet water behind a rocky shoal in the large, deep-channeled Ocmulgee River (near Hawkinsville, Georgia). Several individuals ofspiniferwere seen in the Flint River (near Bainbridge, Georgia), which had a swift current in a wide, deep channel, sandy or sand-silt banks, few brush piles along shore and many oölitic, submergent snags on an otherwise sandy bottom; the water was exceedingly clear and permitted water-goggling (this habitat has been obliterated by a dam on the Apalachicola River). A large femalespiniferwas taken on a set line from the bottom of one of several deep holes (approximately seven feet) that were connected by shallow areas or riffles (near headwaters of Escambia River—Escambia Creek, Escambia County, Alabama). Two large females ofspinifer(one escaped) were taken on a trotline set in a large,[544]deep, isolated barrow pit near the Escambia River (near Century, Florida); there was no aquatic vegetation, the water was slightly turbid, and the substrate was of a sand-silt or mud.In Arkansas,spiniferhas been taken in large deep rivers having relatively clear water, a moderate current, steep banks four to 15 feet high, and a substrate of mud with few rocks (one taken on trotline, escaped; Black River, near Black Rock, Lawrence County). Twospiniferwere taken (trotline and hoop-net) from a smaller (approximately 50 feet wide) turbid river having a swift current, débris along the shoreline, and mud-gravel banks (Petit Jean Creek, Yell County). Severalspiniferandmuticuswere taken from the White River (Marion County) having a sand-gravel or bed rock bottom and clear water; individuals were collected by hand in shallow water (approximately 31/2feet deep) as they lay on the bottom in the main channel where the current was moderate to swift or in a quiet-water side channel having submergent vegetation.Lake Texoma, an impoundment on the Red River, having a fluctuating water level with no permanent stand of aquatic vegetation, a mud-rock or sand-silt bottom, and turbid water (Pl. 49, Fig. 1) is a suitable habitat forspiniferandmuticus.T. spiniferis found in large rivers having relatively clear water, moderate currents, emergent logs and débris, and mud or sand banks (Little River, McCurtain County, Oklahoma,Pl. 48, Fig. 1), or small, shallow, turbid creeks having sand-gravel channels of pools connected by riffle areas (Mayhew Creek, Choctaw County, Oklahoma).Threespiniferwere taken from the Llano River (near Llano, Texas) in a period of low water level in hoop-nets set in a large quiet-water pond about four feet deep and having patches of rushes encroaching into the water from the shore. The river bed of sand, gravel and large boulders consisted of narrower, swift-water channels, small pools and riffles, and large ponds.Individuals ofT. s. emoryihave been taken in large ponds having little or no current, turbid, deep water, and clay or sand-gravel banks (Río Purificación, Padilla, Tamaulipas). Twoemoryiwere collected from a large pond (Río Sabinas, near Sabinas, Coahuila), which was connected to an adjoining one by riffle areas and had little or no current, relatively clear, greenish water, clay or mud banks, a sand-gravel bottom, and was flanked by brush and large cypress trees. A fewemoryiwere trapped in hoop-nets that were set in the Río Mesquites, a stream in central Coahuila approximately 20 feet wide and six feet deep, flanked by dense stands ofPhragmites, and having a moderate current, relatively clear, pea-green water and a mud-sand substrate with some gravel; the stream enlarged in some places to form quiet-water coves (Pl. 48, Fig. 2). One adult maleemoryiwas taken from a crystal-clear, dendritic, pond (El Mojarral, near Cuatro Ciénegas, Coahuila), having shallow areas averaging about two feet but several deep holes—in one of these at the west end of the pond the water was being emitted under pressure from an underwater cavern and "bubbling" at the surface; the vegetation consisted of scattered patches of water-lilies and stonewort; the bottom was a soft mud-marl, and in some places was carpeted with shells of small gastropods. This habitat corresponds to that of the type locality ofT. ater(Pl. 49, Fig. 2); see description in Webb and Legler (1960:26). The water of the ponds is warm; at 8 p. m. on July 31, 1959, the temperature of the water at the type locality ofaterwas 29° C., and the air was 27° C.An immature femalespiniferwas taken on a trotline in a swift, clear, cold-water[545]habitat having mud banks and an abundance of brush piles (Little Tennessee River, Monroe County, Tennessee).T. spiniferoccurs also in large ox-bow lakes having relatively clear water, extensive mats of submerged vegetation, a soft mud bottom, and several emergent stumps and fallen logs (Lake Concordia, Concordia Parish, Louisiana); alligator grass and cypress trees encroached to the shoreline.Locality data of some individuals ofspinifer,hartwegi,asper,pallidusandemoryithat were examined indicated that turtles were captured in ponds, bayous, sloughs, lakes, impoundments, rivers and creeks, indicating habitation of essentially all permanent waters.A juvenile ofhartwegiwas seen by Mr. Wendell L. Minckley on a gravel bar jutting into a small, shallow creek having a mud-gravel bottom (Carnahan Creek, Pottawatomie County, Kansas); the impounding of the Big Blue River by the Turtle Creek Dam will obliterate this habitat. Mr. J. Knox Jones, Jr. reported seeing a large softshell in a narrow, shallow, clear sandy creek in Holt County, Nebraska.T. s. emoryioccurs in large rivers having generally turbid waters, a moderate to swift current and mud or sand bottoms such as the Río Grande; this habitat corresponds to that of large rivers in the western parts of the range ofT. s. pallidus(Red and Washita) andT. s. hartwegi(Canadian and Cimarron). These last-named rivers, in periods of low water level, often have shallow, clear, flowing water in parts of the river bed.T. s. emoryihas also been taken from small creeks having bottoms of rocks and large boulders (Black River Village, Eddy County, New Mexico; field notes of Sydney Anderson and Kenneth Shain, June 12-14, 1958).I received a hatchlingT. s. guadalupensisthat was obtained in a clear, shallow-water stream (Hondo Creek, Bandera County, Texas, on April 12, 1958). The larger streams and rivers known to be inhabited byguadalupensisare generally clear having greenish-tinted waters. The geographic distribution ofguadalupensisindicates that that subspecies occurs principally in those waters that drain the limestone-mantled, Edward's Plateau off the Balcones Escarpment; the headwaters are characterized by clear, calcareous streams having occasional travertine deposits. It is probably this type of habitat to which Agassiz's statement (1857:408) of "clear, bold and rocky streams" refers.There are a few specimens whose locality data indicate a tolerance of brackish-water habitats. An adult malespiniferwas obtained at Delacroix Island, St. Bernard Parish, Louisiana, a locality said to have exceedingly brackish waters (Dr. George H. Bick, St. Mary's College, Notre Dame, Indiana); this adult male (TU 16170) is unique in having a mottled and blotched pattern. Another adult male (spinifer, TU 16071) was obtained in shallow water in Lake Pontchartrain at the mouth of Tchefuncta Creek; the salinity at the time of capture was recorded as 1.7 (datum from Dr. Royal D. Suttkus, Tulane University), indicating only slightly brackish water. Twospinifer(USNM 100409-10) and onemuticus(USNM 100406) were taken at Berwick Bay, near Morgan City, St. Mary's Parish, Louisiana; the waters at this locality are probably brackish. The tolerance of brackish waters doubtless facilitates the dispersal of these turtles along coastal marshes and swamps, and into adjacent drainage systems. The greater number of records in the literature pertaining toferoxsuggest that this species may be more tolerant of brackish and marine waters than arespiniferormuticus.
Cagle (1954:181) wrote that softshells "inhabit the extreme headwaters and smaller tributaries." Other statements in the literature indicate the variety in kinds of habitat. In Louisiana, Beyer (1900:44) mentionedspiniferas abundant "in all inland waters, preferring, however, such bayous which have sloping and sandy banks upon which they are fond of sunning themselves." Viosca (1923:41) reported soft-shelled turtles as characteristic "of the large silt-bearing rivers … such as the Pearl, Amite, Mississippi and Atchafalaya." Cagle and Chaney (1950:386) wrote thatspiniferin Louisiana was found in greatest abundance in streams having some current, but that individuals were also common in quiet areas; the habitats recorded were: False River—a lake of clear water supporting an abundance of submerged vegetation, the shallow ends having mats of water hyacinth; Lakes Iatt and Bistineau—cypress swamps having clear or muddy water; Caddo Lake—a large lake having a light oil film on the surface of the water, and vegetation toward the shore consisting of cattails, water lilies and water hyacinths, and along the bank of cypress and willow trees; Caddo Lake Spillway—muddy with swift current; Sabine River—swift current, traps set in quieter backwater areas or near cypress logs in river; Lacassine Refuge—traps set in inlets and coves of ship channel having vegetation of water hyacinth, alligator grass, and along bank, saw grass, cypress knees and snags. Stejneger (1944:59) reportedspinifertaken in barrow pits in Mississippi.
[542]
In Southern Illinois, Cagle (1942:160) recordedspiniferin drainage ditches (normally having several feet of water and a lush growth of aquatic vegetation) that connect inland swamps to the Mississippi flood-plain but dry up periodically, and in Elkville Lake, an artificial lake having much aquatic vegetation in shallow areas (op. cit.:157). Myers (1927:339) recorded aspiniferfrom Indiana from a "tiny brook." In east-central Illinois P. W. Smith (1947:39) recordedspiniferin mud-bottomed dredge ditches, lakes, ponds, small streams and rivers, whereasmuticuswas found to prefer rivers having clean, sandy bottoms and was not taken from lakes or small streams. This restriction in habitat preference ofmuticusis again emphasized by Smith and Minton (1957:346) who wrote that in Illinois and Indiana,muticus"generally avoids lakes and minor streams." Weed (1923:48), however, recordedmuticus(andspinifer) from Meredosia Bay, Illinois, presumably a broad, shallow, muddy ox-bow lake of the Illinois River.
In Minnesota,spiniferhas been taken from the Mississippi River, which is described as fairly swift having a fluctuating water level, sandy islands, mud banks, a bed of pebbles and large boulders, and abundant crawfish (Breckenridge, 1955:5). In Michigan, Edgren (1942:180) recordedspiniferfrom a "very small muck-bottomed lake." Evans and Roecker (1951:69) recordedspiniferfrom Long Point, Lake Ontario, which is a "broad sand spit, straight on the lakeward side but irregular with wet flats and lagoons on the bayside."
In Kansas, Brumwell (1951:207-08) found "mostly young [muticus] … in the old ponds left during flood stages of the Missouri River" … andspiniferoccasionally … "in the backwaters where stagnant ponds had been formed." In southcentral Kansas, Burt (1935:321) reportedmuticusfrom "a sandbar at junction of a small creek and Medicine River" … and … a "shallow sand-bottomed, algae-filled pasture streamlet." The same author reportedspiniferfrom a "sand-bottomed prairie streamlet" … and … "an alga-filled pool near a stream." Burt (loc. cit.) remarked that "No ecological differences in general habitat and field behavior ofmuticaandspiniferare evident in Kansas." Clarke (1958:21) observedspiniferin Long Creek (Osage County, Kansas), which is a winding stream, characterized by numerous deep holes alternating with rocky riffles, and having high and wooded banks, and mostly mud bottom but occasional rock bottom.
Marr (1944:490) mentioned aspiniferthat was obtained on the bank of a small, mud-bottomed stream in the Texas panhandle, and Linsdale and Gressitt (1937:222) recordedspiniferfrom irrigation canals in Baja California.
In southern Florida,feroxoccurs in all fresh-water habitats (Duellman and Schwartz, 1958:272). Carr (1940:107) reportedferoxas widely distributed in streams, lakes, big springs and canals. Judging from the numbers of turtles, "the larger canals in the Everglades must represent something like an optimum habitat" (Carr, 1952:417). Wright and Funkhouser (1915:119) wrote that in the Okefinokee Swamp,feroxwas especially abundant where the water is deep and the bottom soft, and the species was found wherever there were alligators. Deckert (1918:31) wrote that youngferoxwere taken in springs and brooks near Jacksonville, Florida. Marchand (inCarr, 1952:417-19) observedferoxwhile water-goggling in Florida and noted that individuals buried themselves in deep water in white sand, mud or bubbling mud-sand springs, sometimes where there was vegetation overhead.[543]Neill (1951:16) collectedferoxin marshes, "prairies," flood-plain lakes, lagoons, ox-bow lakes, mangrove swamps, rivers, creeks, calcareous spring runs, man-made lakes and lime sinks. The same author (loc. cit.) reported takingagassizi(=asper) in large muddy rivers, clear "blackwater" streams, calcareous spring runs, creeks, marshes, lagoons, ox-bow lakes, flood-plain lakes, lime sinks, man-made lakes, and smaller ponds. Crenshaw and Hopkins (1955:16), however, stated that in the area whereT. feroxandT. spinifer asperoverlap, "asperis nearly always an inhabitant of fluviatile situations whereasferoxis equally closely confined to non-fluviatile lakes and ponds"; in the region of sympatry, Schwartz (1956:8) reportedferoxfrom "a moderately fast, blackwater stream [Combahee River, South Carolina]."
Carr (1952:417) wrote thatferoxis not uncommon near the mouths of streams in brackish waters, where the tide must occasionally take it to sea, and cited Conant, who told of an individual found at sea in Bahaman waters; Carr (1940:25) listedferoxas occasional in the marine-littoral, mangrove swamps, as did Neill (1951:16). Neill (1958:26-27) mentioned his observance offeroxat the mouth of the Pithlachascotee River, Pasco County, Florida, where the water is sufficiently saline to favor the growth of oysters, and added that commercial fishermen had told him that these turtles are sometimes netted with loggerhead sea turtles (Caretta) in the Indian River. Neill (op. cit.:5-6) also noted the presence offeroxon Meritt Island, which supports an extensive saltwater herpetofauna, off the coast of Brevard County, Florida. Löding (1922:47) recordedspiniferfrom Fig Island, Mobile County, Alabama, which is probably a marine or brackish water habitat. Cagle and Chaney (1950:386) obtained onespiniferin a brackish marsh of the Sabine Wildlife Refuge, Louisiana; the poor trapping returns here (oneTrionyxand onePseudemysin 408 trap-hours) suggest that fresh-water species are not abundant in brackish habitats. Neill (1958:26-27) has summarized the occurrence of soft-shelled turtles in marine and brackish habitats.
My own observations indicate a variety of habitat preferences; the term "relatively clear" refers to waters in which visibility extends four to six inches below the surface at night using a head-light.
Individuals ofspiniferhave been taken in large, deep rivers having a moderate to swift current, relatively clear water, mostly sand and clay bottoms, and emergent débris intermittent along the shoreline; the banks may be steep and of mud having a sparse growth of herbs (Black Warrior River, south of Tuscaloosa, Alabama), or of low extensive, sandy bars and beaches (Escambia River, near Century, Florida,Pl. 50, Fig. 1). A juvenilespiniferwas taken by hand among rocks in quiet water behind a rocky shoal in the large, deep-channeled Ocmulgee River (near Hawkinsville, Georgia). Several individuals ofspiniferwere seen in the Flint River (near Bainbridge, Georgia), which had a swift current in a wide, deep channel, sandy or sand-silt banks, few brush piles along shore and many oölitic, submergent snags on an otherwise sandy bottom; the water was exceedingly clear and permitted water-goggling (this habitat has been obliterated by a dam on the Apalachicola River). A large femalespiniferwas taken on a set line from the bottom of one of several deep holes (approximately seven feet) that were connected by shallow areas or riffles (near headwaters of Escambia River—Escambia Creek, Escambia County, Alabama). Two large females ofspinifer(one escaped) were taken on a trotline set in a large,[544]deep, isolated barrow pit near the Escambia River (near Century, Florida); there was no aquatic vegetation, the water was slightly turbid, and the substrate was of a sand-silt or mud.
In Arkansas,spiniferhas been taken in large deep rivers having relatively clear water, a moderate current, steep banks four to 15 feet high, and a substrate of mud with few rocks (one taken on trotline, escaped; Black River, near Black Rock, Lawrence County). Twospiniferwere taken (trotline and hoop-net) from a smaller (approximately 50 feet wide) turbid river having a swift current, débris along the shoreline, and mud-gravel banks (Petit Jean Creek, Yell County). Severalspiniferandmuticuswere taken from the White River (Marion County) having a sand-gravel or bed rock bottom and clear water; individuals were collected by hand in shallow water (approximately 31/2feet deep) as they lay on the bottom in the main channel where the current was moderate to swift or in a quiet-water side channel having submergent vegetation.
Lake Texoma, an impoundment on the Red River, having a fluctuating water level with no permanent stand of aquatic vegetation, a mud-rock or sand-silt bottom, and turbid water (Pl. 49, Fig. 1) is a suitable habitat forspiniferandmuticus.T. spiniferis found in large rivers having relatively clear water, moderate currents, emergent logs and débris, and mud or sand banks (Little River, McCurtain County, Oklahoma,Pl. 48, Fig. 1), or small, shallow, turbid creeks having sand-gravel channels of pools connected by riffle areas (Mayhew Creek, Choctaw County, Oklahoma).
Threespiniferwere taken from the Llano River (near Llano, Texas) in a period of low water level in hoop-nets set in a large quiet-water pond about four feet deep and having patches of rushes encroaching into the water from the shore. The river bed of sand, gravel and large boulders consisted of narrower, swift-water channels, small pools and riffles, and large ponds.
Individuals ofT. s. emoryihave been taken in large ponds having little or no current, turbid, deep water, and clay or sand-gravel banks (Río Purificación, Padilla, Tamaulipas). Twoemoryiwere collected from a large pond (Río Sabinas, near Sabinas, Coahuila), which was connected to an adjoining one by riffle areas and had little or no current, relatively clear, greenish water, clay or mud banks, a sand-gravel bottom, and was flanked by brush and large cypress trees. A fewemoryiwere trapped in hoop-nets that were set in the Río Mesquites, a stream in central Coahuila approximately 20 feet wide and six feet deep, flanked by dense stands ofPhragmites, and having a moderate current, relatively clear, pea-green water and a mud-sand substrate with some gravel; the stream enlarged in some places to form quiet-water coves (Pl. 48, Fig. 2). One adult maleemoryiwas taken from a crystal-clear, dendritic, pond (El Mojarral, near Cuatro Ciénegas, Coahuila), having shallow areas averaging about two feet but several deep holes—in one of these at the west end of the pond the water was being emitted under pressure from an underwater cavern and "bubbling" at the surface; the vegetation consisted of scattered patches of water-lilies and stonewort; the bottom was a soft mud-marl, and in some places was carpeted with shells of small gastropods. This habitat corresponds to that of the type locality ofT. ater(Pl. 49, Fig. 2); see description in Webb and Legler (1960:26). The water of the ponds is warm; at 8 p. m. on July 31, 1959, the temperature of the water at the type locality ofaterwas 29° C., and the air was 27° C.
An immature femalespiniferwas taken on a trotline in a swift, clear, cold-water[545]habitat having mud banks and an abundance of brush piles (Little Tennessee River, Monroe County, Tennessee).T. spiniferoccurs also in large ox-bow lakes having relatively clear water, extensive mats of submerged vegetation, a soft mud bottom, and several emergent stumps and fallen logs (Lake Concordia, Concordia Parish, Louisiana); alligator grass and cypress trees encroached to the shoreline.
Locality data of some individuals ofspinifer,hartwegi,asper,pallidusandemoryithat were examined indicated that turtles were captured in ponds, bayous, sloughs, lakes, impoundments, rivers and creeks, indicating habitation of essentially all permanent waters.
A juvenile ofhartwegiwas seen by Mr. Wendell L. Minckley on a gravel bar jutting into a small, shallow creek having a mud-gravel bottom (Carnahan Creek, Pottawatomie County, Kansas); the impounding of the Big Blue River by the Turtle Creek Dam will obliterate this habitat. Mr. J. Knox Jones, Jr. reported seeing a large softshell in a narrow, shallow, clear sandy creek in Holt County, Nebraska.
T. s. emoryioccurs in large rivers having generally turbid waters, a moderate to swift current and mud or sand bottoms such as the Río Grande; this habitat corresponds to that of large rivers in the western parts of the range ofT. s. pallidus(Red and Washita) andT. s. hartwegi(Canadian and Cimarron). These last-named rivers, in periods of low water level, often have shallow, clear, flowing water in parts of the river bed.T. s. emoryihas also been taken from small creeks having bottoms of rocks and large boulders (Black River Village, Eddy County, New Mexico; field notes of Sydney Anderson and Kenneth Shain, June 12-14, 1958).
I received a hatchlingT. s. guadalupensisthat was obtained in a clear, shallow-water stream (Hondo Creek, Bandera County, Texas, on April 12, 1958). The larger streams and rivers known to be inhabited byguadalupensisare generally clear having greenish-tinted waters. The geographic distribution ofguadalupensisindicates that that subspecies occurs principally in those waters that drain the limestone-mantled, Edward's Plateau off the Balcones Escarpment; the headwaters are characterized by clear, calcareous streams having occasional travertine deposits. It is probably this type of habitat to which Agassiz's statement (1857:408) of "clear, bold and rocky streams" refers.
There are a few specimens whose locality data indicate a tolerance of brackish-water habitats. An adult malespiniferwas obtained at Delacroix Island, St. Bernard Parish, Louisiana, a locality said to have exceedingly brackish waters (Dr. George H. Bick, St. Mary's College, Notre Dame, Indiana); this adult male (TU 16170) is unique in having a mottled and blotched pattern. Another adult male (spinifer, TU 16071) was obtained in shallow water in Lake Pontchartrain at the mouth of Tchefuncta Creek; the salinity at the time of capture was recorded as 1.7 (datum from Dr. Royal D. Suttkus, Tulane University), indicating only slightly brackish water. Twospinifer(USNM 100409-10) and onemuticus(USNM 100406) were taken at Berwick Bay, near Morgan City, St. Mary's Parish, Louisiana; the waters at this locality are probably brackish. The tolerance of brackish waters doubtless facilitates the dispersal of these turtles along coastal marshes and swamps, and into adjacent drainage systems. The greater number of records in the literature pertaining toferoxsuggest that this species may be more tolerant of brackish and marine waters than arespiniferormuticus.
In summary,T. feroxoccurs in all fresh-water habitats, but chiefly in lentic habitats in the northern part of its range where it andT. s. asperare sympatric.T. feroxpossibly is more tolerant of brackish and marine waters than are the subspecies ofspiniferandmuticus.
The subspecies ofT. spiniferoccur in all fresh-water habitats. In the southern part of the geographic range, which overlaps that ofT. ferox,T. s. asperoccurs principally in running-water habitats.T. s. pallidusandT. s. asperare tolerant of brackish-water habitats.T. s. guadalupensis, known at present only from rivers and streams, occurs principally in river systems that drain the Edward's Plateau of southcentral Texas.T. ateris confined to crystal-clear ponds in central Coahuila.
The subspeciesmuticusoccurs in large rivers and streams throughout its geographic range, but is known from lakes and impoundments principally in the southern part of its range (the northernmost record is from Reelfoot Lake, Obion County, Tennessee); there is only one record ofmuticusfrom a small, shallow, headwater creek (Reno County, Kansas), and only one from a lentic habitat (Meredosia Bay, Illinois) in the northern part of its range.T. muticus calvatusis known at present only from rivers and streams.
The seemingly greater restriction ofmuticusto running-water habitats suggests less vagility than inspinifer(Netting, 1944:86).
Size and coloration are adaptations to habitat. Soft-shelled turtles of large size are best adapted to mesic, essentially continuous swampy or marshy habitats, whereas small size is an adaptation to less continuous, semi-isolated habitats. A turtle of the maximum size attained byferoxin the habitat ofemoryiwould, in a general way, probably be more conspicuous and exposed to its enemies, both in the aquatic environment and during overland excursions; perhaps the kind and amount of food would be insufficient. In any event, small size is correlated with the more arid habitats of the southwest, and large size with mesic ones in the southeast.T. ferox, the largest species, and the smallest population ofT. spinifer(resemblingmuticus) both occur in the southernmost part of the range of the genus. This situation does not support the corollary of Bergmann's Rule, that pertains to some groups of terrestrial reptiles, in which those subspecies occurring farther north, or in cooler climates during their season of activity, tend to be smaller.
Within the speciesspinifer, theemoryigroup of subspecies are pallid having whitish dots on the carapace and lack extensive black pigmentation; these features seem to confer protective coloration on the inhabitants of arid, essentially sandy or muddy habitats havingsluggish, turbid waters, whereas the more contrasting patterns of thespinifergroup of subspecies eastward seem more suited to existence in clearer, swifter waters.
The occurrence of the two clines,spinifer-hartwegiandpallidus-guadalupensis, in the speciesspiniferare notable in that the former occurs mostly in one large continuous drainage system, that of the Mississippi, and shows no sharp break in the one character distinguishing the two subspecies whereas populations composing thepallidus-guadalupensiscline are separated into several river drainages, and show a relatively sharp break in several characters at the Brazos-Colorado river divide. This situation seemingly supports the thesis that clines are maintained by some sort of parallel gradient in ecological or geological conditions. It is notable that streams draining the Edward's Plateau (inhabited byguadalupensis) differ in quantity (more) and quality (especially CO_{3}—, Ca++, and Mg++ions) of their solutes, and probably pH (higher) from those farther east (Hubbs, 1957:102). The gross difference in habitats mentioned above (sandy, turbid, sluggish streams in the westvs.clear, swift streams in the east) may affect the differentiation recognizable in thespinifer-hartwegicline.
Daily and Seasonal Activity
Diurnal Habits
Softshells bask on débris in the water or on banks close to the water; basking presumably raises the bodily temperature. In general in the southeastern and southwestern United States, I have seen softshells basking only rarely but once saw six at one time close together on logs in Bowie Creek, Hattiesburg, Mississippi (species undetermined). Surface (1908:122) sawspiniferin rows on rocks or logs in tributaries of the Ohio River. Duellman and Schwartz (1958:271-72) stated thatferoxbasks on banks or beds of aquatic vegetation. Deckert (1918:31) mentioned largeferox"sunning in shallow water at edge of pond." Minton (1944:447) wrote thatmuticusandspinifersun on steep mud banks (Wabash River). Cahn (1937:180) stated thatmuticus(in Illinois) basks on banks at the water's edge but seldom on logs, and suggests thatmuticusis less prone to leave the water thanspinifer. According to Carr (1952:438),muticusnever basks on logs or rocks. In Ohio, Conant (1951:159) mentionedspiniferas occasionally basking upon a log or rock, or sometimes on steep clay banks of streams. On banks, quick escape is facilitated by directing the head toward the water, thus eliminating the time that it wouldtake to turn around on land (Conant,loc. cit.; Newman, 1906:129). Evermann and Clark (1920:593) mentionedspiniferas basking on sandy or grassy shores, and large boulders. Muller (1921:181) wrote thatmuticusbasks four to ten feet from the water's edge on gently sloping sand and mud shores of small islands in the Mississippi River (near Fairport, Iowa). Muller stated that basking usually occurs in the morning, up until 2 p. m., and that beaches with a northern exposure were preferred; he observed 37 turtles within a 50-foot stretch of beach. In captivity, hatchlings bask on wire-mesh supports.
I have frequently observed softshells floating at the surface of the water, a habit previously mentioned by Surface (1908:122) and Pope (1949:305, 311). Individuals ofPseudemysand, to a lesser extent,Graptemysalso float at the surface; those kinds of turtles and softshells at least, often appear at the surface of the water, seemingly as a result of an inquisitiveness, following repeated disturbances that cause submergence.
Newman (1906:131) described the active pursuit of food: "They crawl or swim along the bottom, thrusting their snouts under stones and into masses of aquatic vegetation, occasionally snapping up a crayfish or larva that they have succeeded in dislodging. They do not tear up their food, but swallow it whole, using the forefeet to assist in forcing it down." Surface (1908:123) suggested that softshells may feed "upon insects which may be found floating on the water," and I have had captives take insects from the surface of the water. Carr (1940:107) also wrote thatferoxand numerous gars in the Tamiami Canal, often at the mouths of the tributary ditches, snap at each other furiously as floating bits of food are washed in from the Everglades. Another habit that has been mentioned as an aid in acquiring food (Breckenridge, 1944:186; Conant, 1951:156; Hudson, 1942:101) is burrowing just below the surface in a soft bottom in shallow water, to ambush passing fish, or other food. Presumably all kinds of softshells do this in both shallow and deep water of lakes or rivers having a suitable substrate;spiniferandmuticushave been reported to burrow in shallow waters (no observations in deep water) by Agassiz (1857:333), Cahn (1937:180, 189), Conant (1951:159) and Weed (1923:48). Marchand (inCarr, 1952:417-19) noted thatferoxburrows in deep water, and mentioned that in areas of bare white sand a group of fish invariably surrounds them, and one can locate buried softshells by observing these particular schools of fish. No mention was made of the turtles attempting to catch the fish. Other associations of soft-shelledturtles and fish have been described. Kirtland (inDeKay, 1842:7) observed several large bass that closely followed large numbers of turtles floating at the surface. Newman (1906:131) reported the observations of fishermen in Lake Maxinkuckee that large-mouth black bass stay not far away from swimming softshells; the same author also mentioned the observations of Jacob Reighard, who suggested that bass may be feeding upon minnows that he noticed following softshells. Seemingly some sort of commensalistic relationship exists whereby fish acquire food that is dislodged by grubbing and scurrying of softshells. Probably food is pursued on occasion from a buried position, but this habit probably is not executed specifically for obtaining food. Newman (op. cit.:129) was of the opinion that burrowing in shallow water is a habit to facilitate "warming up."
Marchand (loc. cit.) also wrote of other notable underwater observations onferoxin Florida. He commented on this turtle's inquisitiveness in deep water and unconcern upon being touched or even upon being handled to some degree. Calf-deep in soft mud, he noted a turtle that "emerged from the mud of the bottom, headed up toward shore, circled, and when about three feet above the bottom dived suddenly and completely disappeared." Marchand wrote that some areas on the bottom (Crystal Springs), which are rooted up by the burrowing of softshells, are bare and soft, and assume a characteristic, easily recognized, appearance.
Cahn (1937:180, 189) stated that the burrowing process consists of "flipping" the loose sand or silt over the back, whereas Conant (1951:159) described the process as a rapid lateral movement of the body. My observations of captives agree essentially with Conant's observations. The initial movement, directed at a slight angle, is principally with the forelegs although complemented by lateral movements of the body. When the turtle is approximately half buried, it makes rapid lateral movements of the body, which completely bury the turtle and orient its body in a horizontal position.
Behavior and Adaptations
Some characteristics of softshells that are often mentioned in the literature are: extreme shyness or wariness, ferociousness as captives, dazzling speed and agility on land and in water, and great dependence on aquatic environment. Certainly they are wary; and this wariness may account, in part, for the scarcity of observations of basking, and statements attesting to their great speed on land. To my mind, their reported ferociousness and savage dispositionas captives is overrated; of the many softshells that I have collected, only a few attempted to bite. The extensibility of their long neck does warrant more careful handling than needs to be employed with other species. Holbrook (inHay, 1892:145) even wrote that they "will sometime leap up and give a loud hiss," and Newman (1906:130) wrote that "they hiss violently and thrust out the head." Wright and Funkhouser (1915:120) reported a captiveferoxthat "could jump forward practically its own length." I have been bitten by individuals ofKinosternon,Sternothaerus,PseudemysandGraptemys, and cannot support the contention that softshells are more prone to bite than those species, a view shared by LeConte (inDeKay, 1842:7); many softshells on initial capture will tend to withdraw the head completely for a short time. Newman (loc. cit.) also wrote that recently captured specimens exude a thick, yellow, semi-fluid resembling yolk of an egg from the inguinal glands; the substance, however, is odorless but "undoubtedly homologous with the emission of the inguinal glands of the musk and snapping tortoises." Perhaps there is a difference in aggressiveness associated with geographic location, the age of the turtle or individual temperament.
Smith (1956:159), referring tomuticus, wrote that they are the best swimmers of all fresh-water turtles, and perhaps of any turtles. Corresponding statements of other authors attesting to their speed and agility (includingspiniferandferox) in water and on land are based principally on the published comments of Muller (1921:181), who observed that females disturbed while laying eggs "about fifty feet from water … covered the distance faster than a man can run." Cahn (1937:180) also stated thatmuticuson a "level, unobstructed sand beach … can outrun a man," and (op. cit.:181) can "capture fish with ease"; Cahn supported the latter statement by relating his observation of amuticusthat captured a small brook trout in a large tank. Smith (op. cit.:162) wrote thatspiniferis "said to overtake bass." Doubtless they are good swimmers and they do scurry rapidly on land.
Published statements relating to the strictly aquatic existence of softshells especiallymuticus, are based on recognition of "its drastic adaptations to aquatic existence" (Carr, 1952:428); these adaptations presumably include pharyngeal respiration and the marked depression of body form. Pharyngeal respiration was demonstrated formuticusandspinifer(Gage, 1884; Gage and Gage, 1886), and was considered the principal type of aquaticrespiration (some dermal and some cloacal) inTrionyx spinifer asperby Dunson (1960). Cloacal bursae (anal respiration) are lacking in trionychids (Smith and James, 1955:88). Accessory pharyngeal respiration is meaningful in light of the information furnished by Agassiz (1857:282-83), who found thatTrionyxhas a smaller lung capacity (weight of body in ounces/capacity of lungs in cubic inches = 16.9) than do some other genera (Pseudemys, 2.8;Testudo, 2.7;Terrapene, 1.1); corresponding values for more aquatic species wereChelydra, 9.3 andKinosternon, 16.0. Cahn (1937:181), however, wrote that he has demonstrated pharyngeal respiration in individuals ofPseudemys,ChrysemysandSternothaerus, and Allen and Neill (1950:13) suggested that it occurs inMacroclemys. More conclusive data are required to detect a positive correlation between small lung capacity, pharyngeal respiration, and degree of restriction to an aquatic habitat.