Remarks.—Smith (1941:121-122) describedC. pulcher plagosusfrom Tonalá, Chiapas, and characterized the subspecies by its having "(1) the ventrals completely unspotted; (2) secondary lines on paravertebral rows not continuous posteriorly; (3) all other lines on body also somewhat spotted in appearance; (4) dusky markings on chin and supralabial border very dim (less distinct than inp. pulcheror any member of thelineatusseries)." Although all Chiapan specimens lack ventral spots, specimens from Guatemala have no spots, small spots, or large spots. Even in specimens from Tegucigalpa, Honduras, the southernmost limit of the range,the spotting varies from a few inconspicuous spots to many large spots. Paravertebral rows were continuous posteriorly in alimens examined by me. Likewise, all other stripes were continuous bands of uniform width posteriorly, having appeared anteriorly as rows of spots or dashes. The amount of brown on the chin and labials has been shown previously not to be geographically significant. The absence of characters of adequate significance to separate populations precludes the naming of subspecies in this species.Mertens (1952a:93, and 1952b:61-62) designated three specimens from El Salvador asC. pulcher plagosus. In the latter paper, Mertens, on the basis of a description of a specimen of "C. lineatus" from Divisadero, El Salvador, given by Schmidt (1928:200), referred that specimen also toC. pulcher plagosus. I have examined this specimen and refer it toC. lineatus dunni. Although I have not seen Merten's specimens, on the basis of the excellent descriptions given by Mertens (1952b:61-62), I refer the three Salvadoranean specimens toC. lineatus dunni.The presence of paravertebral stripes in combination with the characteristics of the genus distinguishConophis pulcherfrom all other snakes in southern México and Central America. The only sympatric species of this genus,C. lineatus dunni, differs in that it lacks paravertebral stripes, although it may have a single vertebral stripe.Conophis lineatus dunnihas lateral dark stripes that are present on the 3rd and 4th scale-rows, never on the anterior third of the body as inC. pulcher. Even in juveniles the third pair of dark stripes includes the lower part of the 9th scale-row inC. pulcher, whereas the dorsal most dark stripe ofC. lineatus dunninever includes more than the lower part of the 8th scale-row.Distribution.—Pacific coastal region of Chiapas, México, southeastward into Guatemala; southeastern highlands and the dry valley of central and eastern Guatemala; Caribbean lowlands of Honduras southward to the region of Tegucigalpa, Honduras (fig. 4).Specimens examined.—Total of 27, as follows:Guatemala:no specific locality, CNHM 22912, NMW 16830.Jutiapa: Hacienda Mongoy, UMMZ 106725.El Progreso: El Progreso, CAS 67000;El Rancho, UMMZ 106724;San Antonio, CAS 66999. "Peten," USNM 6751(2), 6803.Sacatepequez: Dueñas, BMNH 64.1.26.17, 64.1.26.126-127.Zacapa: Pepesca, AMNH 72555-56.Honduras:no specific locality, AMNH 58364.Cortes: San Pedro Sula, CNHM 5295-96.Francisco Morazan: El Zamarano, AMNH 70189; Tegucigalpa, MCZ 49785, 49787-88, 49791, 49793, 49795.México:Chiapas:Soconusco, UIMNH 33646-47; Tonalá, USNM 109707.Conophis vittatusPetersTomodon lineatum(in part), Duméril, Bibron andDuméril,Erpétologie Générale, 7(pt. 2):936-938, February 25, 1854.Conophis vittatusPeters, Monatsb. Akad. Wiss. Berlin, pp. 519-520, pl.,fig. 3, October, 1860; Cope, Proc. Amer. Philos. Soc., 11:162, 1870; BocourtinDuméril, Bocourt and Mocquard, Mission Scientifique au Mexique et dans l'Amerique Centrale, 2:644-646, pl. 38, fig. 7, 1886; Günther, Biologia Centrali-Americana, p. 165, March, 1895; Boulenger, Catalogue of the Snakes in the British Museum (Natural History), 3:123-124, 1896; Cope, Amer. Nat., 30:1024, 1896; Ann. Rept. U. S. Natl. Mus. for 1898, pp. 1094-1095, 1232, 1900; Gadow, Proc. Zool. Soc. London, 2:225, 1905; Amaral, Mem. Inst. Butantan, 4:211, 1929; Gadow, Jorullo, p. 55, 1930; Smith, Zool. Ser. Field Mus. Nat. Hist., 24:31-32, January 30, 1939; Taylor and Smith, Univ. Kansas Sci. Bull., 25:252-253, pl. 23, July 10, 1939; Stuart, Contr. Lab. Vert. Biol. Univ. Michigan, 65:23, March, 1954; Alvarez del Toro, Reptiles de Chiapas, pp. 153-154, 1960.Conophis lineatusCope, Proc. Acad. Nat. Sci. Philadelphia, 16(3):167, 1864 [necDuméril, Bibron and Duméril,Erpétologie Générale, 7(pt. 2):936-938, atlas, pl. 73, February 25, 1854; specimen from Colima]; Sumichrast, Arch. Sci. Nat., p. 246, 1873.Tomodon vittatus, Bocourt, Journ. de Zool., p. 407, 1876.Conophis sumichrasti sumichrastiCope, Journ. Acad. Nat. Sci. Philadelphia, ser. 2, 8:137, 1876 (Types.—United States National Museum, nos. 29123, 30258; type locality.—Tehuantepec, México); Bull. U. S. Natl. Mus., 32:77, 1887; Smith and Taylor, Univ. Kansas Sci. Bull., 33(pt. 2):334, March 20, 1950; Maldonado-Koerdell, Inst. Mexicanos Recursos Nat. Renov., p. 124, 1953.Conophis sumichrasti viduusCope, Journ. Acad. Nat. Sci., Philadelphia, ser. 2, 8:137, 1876 (Type.—United States National Museum, no. 30259; type locality.—Tehuantepec, México); Bull. U. S. Natl. Mus., 32:77, 1887; Cochran, Bull. U. S. Natl. Mus., 220:167, 1961.Conophis sumichrasti, Cope, Proc. Amer. Philos. Soc., 18:271, August 11, 1879; Sumichrast, Bull. Soc. Zool. France, p. 182, 1880; Cope, Trans. Amer. Philos. Soc., 18:194, April 15, 1895; Cochran, Bull. U. S. Natl. Mus., 220:167, 1961.Tachymenis lineata(in part), Garman, Mem. Mus. Comp. Zool., 8:60-61, July, 1884.Conophis vittatus sumichrasti, Cope, Ann. Rept. U. S. Natl. Mus. for 1898, p. 1095, 1900.Conophis vittatus vidensCope, Ann. Rept. U. S. Natl. Mus., for 1898, p. 1095, 1900 (apparentlapusforviduus).Conophis vittatus vittatus, Cope, Ann. Rept. U. S. Natl. Mus. for 1898, p. 1095, 1900; Smith, Journ. Washington Acad. Sci., 31:119-120, March 15, 1941; Proc. U. S. Natl. Mus., 92:395, November 5, 1942; Proc. U. S. Natl. Mus., 93:408, October 29, 1943; Ann. Carnegie Mus., 30:91, November 2, 1944; Smith and Taylor, Bull. U. S. Natl. Mus., 187:44, October 5, 1945; Smith, Rev. Soc. Mexicanos Hist. Nat., 7:71, December, 1946; Smith and Taylor, Univ. Kansas Sci. Bull., 33(pt. 2):331, March 20, 1950; Davis and Smith, Herpetologica, 8:134, January 30, 1953; Maldonado-Koerdell, Inst. Mexicanos Recursos Nat. Renov., p. 130, 1953; Peters, Occas. Papers Mus. Zool. Univ. Michigan, 554:22, June 23, 1954; Duellman, Occas. Papers Mus. Zool. Univ. Michigan, 560:15, October 22, 1954; Webb and Fugler, Herpetologica, 13:35, March 30, 1957; Duellman, Occas. Papers Mus. Zool. Univ. Michigan, 589:15, March 21, 1958; Zweifel, Amer. Mus. Novitates, 1949:2, 5, June 17, 1959; Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 15(1):91-92, December 20, 1961.Conophis vittata, Gadow, Proc. Zool. Soc. London, 2:196, 1905; Through Southern Mexico, p. 181, 1908.Conophis viduus, Smith, Zool. Ser. Field Mus. Nat. Hist., 24:31, January 30, 1939; Hartweg and Oliver, Misc. Publ. Mus. Zool. Univ. Michigan, 47:26-27, July 13, 1940.Conophis vittatus viduus, Smith, Journ. Washington Acad. Sci., 31:120-121, March 15, 1941; Proc. U. S. Natl. Mus., 92:395, November 5, 1942; Proc. U. S. Natl. Mus., 93:408, October 29, 1943; Woodbury and Woodbury, Journ. Washington Acad. Sci., 34(11):370, 1944; Smith and Taylor, Proc. U. S. Natl. Mus., 187:44, October 5, 1945; Univ. Kansas Sci. Bull., 33(pt. 2):340, March 20, 1950; Werler and Smith, Texas Journ. Sci., 4:565, fig. 16, December 30, 1952; Maldonado-Koerdell, Inst. Mexicanos Recursos Nat. Renov., p. 130, 1953; Davis and Dixon, Proc. Biol. Soc. Washington, 72:82-83, July 24, 1959.Conophis vittatus vittatus×Conophis vittatus viduus, Alvarez del Toro and Smith, Herpetologica, 12:13, March 6, 1956.Type.—Zoologisches Museum Berlin. Type locality not given, for the specimen was purchased from a dealer in Hamburg. The type locality was first restricted to "Acapulco," Guerrero, by Smith (1941:119), then to Laguna Coyuca, Guerrero, México, by Smith and Taylor (1950:331).Diagnosis.—Three or four dorsal dark stripes, each involving two or more adjacent scale-rows; never having brown or black on the 1st scale-row; seven supralabials immaculate white or pale tannish-white.Variation.—One hundred seventy-one specimens have 149 to 181 (163.7 ± 6.33) ventrals. One hundred fifty-three of these having complete tails have 55 to 76 (64.8 ± 4.90) subcaudals; the number of ventrals plus subcaudals varies from 214 to 245 (228.5). In 170 specimens the reduction from 19 to 17 dorsal scales takes place between ventrals 84 and 118 (102.3 ± 6.60). Sexual dimorphism is evident in the number of subcaudals; 58 females have 55 to 66 (60.0) and 95 males have 59 to 76 (67.8) subcaudals. The longest specimen (AMNH 68004) is a male from Escurano, Oaxaca, México, having a body length of 668 mm., a tail length of 182 mm. and a total length of850mm. A juvenile (CNHM 40435) fromTehuantepec, Oaxaca, México, has a body length of 133 mm., a tail length of 31 mm. and a total length of 164 mm.Variation in coloration is of such magnitude that it has been used as the basis for recognition of subspecies. Unfortunately, until this time, most specimens reported upon in the literature represented the two extremes of variation. After examining the coloration of 174 specimens with respect to geographic distribution, I conclude that only one highly variable species is represented. Specimens from the northern and western parts of the range (Michoacán, Colima, and Durango) have the color pattern ofC. vittatusas described by Peters (1860:518-521); these snakes have four narrow black stripes on a white or pale tan background, and an immaculate white venter. The lateral dark stripe, which on the head passes through the eye, is present on the dorsal half of the 3rd and the ventral half of the 4th scale-rows; the dorsolateral dark stripe, which passes along the middle of the head and splits on the nape, is present on the middle of the 8th scale-row. The other extreme in color pattern consists of three broad stripes; the two dorsolateral stripes are fused. This pattern is prevalent in specimens from the area around Tehuantepec, Oaxaca. The lateral stripes include the dorsal half to two-thirds of the 2nd, all of the 3rd and 4th, and half of the 5th scale-rows; the fused dorsolateral stripes sometimes cover all of the area dorsal to and including the dorsal third of the 7th scale-row.Snakes from areas between Tehuantepec and the margins of the distributionof this species are variously intermediate between the extremes described above. In some snakes from these areas the lateral stripes are broad and include either the dorsal half of the 2nd scale-row or the ventral half of the 5th scale-row, but not both on the same specimen. Also, the dorsolateral stripes are broad and include most of the 9th and a part of the 10th scale-rows. Many specimens from the area around Tehuantepec, where the three-striped pattern is prevalent, have an intermediate pattern. Some have white on the center of the 10th scale-row or lateral stripes that are not so broad as to include the 3rd and 4th and half of each of the 2nd and 5th scale-rows.The supralabials are immaculate white or pale tan, except that in some specimens the dorsalmost part of some supralabials are dark brown or black as they are included in the ventral boundary of the dark stripe that passes through the eye. There are no dusky markings on the chin or on any of the ventral scales.There is no ontogenetic change in color pattern; juveniles have the same coloration as adults from the same geographic area.Color in life is not greatly different from that of preserved specimens. One specimen (UMMZ 114483) from 10.8 miles south ofOaxaca,had in life black stripes, a pale yellowish tan dorsal ground-color and a pale off-white venter.An excellent photograph of this species appears in Schmidt and Inger (1957:230) under the nameConophis lineatus.Remarks.—I have been unable to find variation of geographic importance in scutellation in this species. A wide range of variation in the characters of scutellation is present in specimens from most localities; it shows no significant clinal or geographic trends. As I have stated previously, in the discussion of variation, coloration has been the feature primarily used by previous workers to distinguish two "subspecies" for this species;C. vittatus vittatushaving four black stripes andC. vittatus viduushaving three black stripes. Most of the three-striped snakes occur in the vicinity of Tehuantepec, Oaxaca, whereas the four-striped snakes are found near the margins of the range of the species in Durango, Colima, Michoacán, Morelos and Puebla. Specimens that would have to be considered intergrades between the "subspecies" are found in Michoacán, Guerrero, Oaxaca and Chiapas. At the time the subspecies were proposed only specimens from Tehuantepec or from marginal areas were known. Utilizing the large number of specimens of this species presently available, geographic variation is found to be clinal, from those with three stripes from near Tehuantepec, through several intermediate patterns present on specimens from single localities in Guerrero, Oaxaca and Chiapas, to those with four dark stripes in areas farthest removed to the north and west from Tehuantepec. Since only coloration shows geographic variation, and since this variation represents a continuous cline, subspecies cannot be recognized for this species.The presence and position of the three or four dark stripes on the body and the absence of brown on the 1st scale-row or on the ventral scales, in combination with the generic characters, distinguishConophis vittatusfrom all other Méxican snakes. The only other snake that occurs in western México that has been confused withC. vittatusisConiophanes piceivittus taylori, which has 25, instead of 19, scale-rows.Distribution.—Semi-arid habitats on Pacific slopes from extreme southern Durango southeastward to Tuxtla Gutierrez, Chiapas, and inland in the eastern Balsas Basin to Morelos and western Puebla (fig. 5).Fig. 5.Selected locality records forConophis vittatus.Specimens examined.—Total of 174, as follows:México:no specific locality, AMNH 66150-52, SU 9465.Chiapas: Piedra Parada, USNM 121453.Pizo de Oro, UIMNH 40821. Tuxtla Gutierrez, Parque Madero, UIMNH 37992-93, 38036-37.Colima: no specific locality, MCZ 46860, USNM 31394, 31396-97. 1 mi. SW Colima, AMNH 12783. S of Manzanillo, AMNH 19641.Durango: Hacienda de Gabriel, AMNH 14217.Guerrero: Acahuizotla, TCWC 7419, 9469.1 mi. W Acahuizotla, TCWC 7418. 3 mi. W Acapulco, AMNH 71626.6 mi. E Acapulco, TCWC 9476-77.10 mi. S Acapulco, TCWC 8578.Agua del Obispo, CNHM 104948, TCWC 11586. near Chilpancingo, MVZ 45067, UMMZ 85722-23.1 mi. SW Colotlipa, TCWC 9471-74.2 mi. SW Colotlipa, TCWC 9475. 14 mi. S Ixtapán de la Sal, KU 67648.Laguna Coyuca, CNHM 25881, UMMZ 80942. near La Unión, AMNH 66337.Magueyes, Laguna Coyuca, AMNH 66149.Playa Encantada, TCWC 9470. 1 mi. S Tierra Colorada, KU 67649. nearXaltinanguis, km. 405, CNHM 104947.Michoacán: Coalcomán, UMMZ 104693.1/2 mi. SE Coalcomán, UMMZ 104492.1 mi. N. Coalcomán, UMMZ 112543.1 mi. NE Coalcomán, UMMZ 104692. Puerta de la Playa, UMMZ 105155. 12 mi. STzitzio (by road), UMMZ 99153.Morelos: 12 km. NW Axochiapan, TCWC 7311, UIMNH 17613, 25924. 7 mi. SE Cuernavaca, MVZ 32258.Huajintlán, km. 133, CNHM 103270. 12 km. S Puente de Ixtla, km. 133, CNHM 104949.Oaxaca: Bisiliana, AMNH 68010.near Caoba, foot of Cerro Arenal, AMNH 68009.Cerro Arenal, AMNH 68000-03.Cerro de Laollaga, UIMNH 36213.Cerro de San Pedro, UIMNH 17616.Cerro Palma de Oro, UIMNH 37116. "C. Madrena, Sto. T. Quieri," UIMNH 46904. near Chivela, MCZ 25021. Cinco Cerros, UIMNH 37114.Dami Liesa, AMNH 66877, UIMNH 6158, 37115.Escuranos, AMNH 66873-74, 68004-06.Finca Santa Teresa, 2 km. NW Tehuantepec, UMMZ 82648.Huilotepec, AMNH 66878, UIMNH 40820.between Huilotepec and Tehuantepec, AMNH 65106, UMMZ 82644-45.Las Tejas, UIMNH 6151-54.Mixtequilla, UIMNH 6157, 36211.between Mixtequilla Mountains and Tehuantepec, UMMZ 82652.between Niltepec and "Carixxal,"AMNH 68876. 10.8 mi. SE Oaxaca, UMMZ 114483.Quiengola, UIMNH 17617.between Quiengola Mountains and Tehuantepec, UMMZ 82647.Rancho Poso Río, 6 km. S Tehuantepec, UIMNH 6144-49, 37117-19, UMMZ 82649-51.Rincón Bamba, CNHM 105129-30, UIMNH 17615.Salazar, AMNH 66875.vicinity of Salina Cruz, UMMZ 82653.San Gerónimo, AMNH 4306, CNHM 1457.San Lucas Ixtepec, UIMNH 36206. San Juan Lajarcia, UIMNH 36212. San Mateo del Mar, AMNH 65914.San Pablo, UIMNH 36207.Santa María (Cerro de Liesa), AMNH 68011. Tapanatepec, MCZ 27806-11. Tehuantepec, AMNH 19644, 65107-09, 65907-13 plus 7, 66871-72, 66879, 68007-08, CNHM 40435-36, 105126-28, MCZ 46403, UIMNH 6150, 17614, 17618, 29692, 36208, 37120-21, UMMZ 82642-43, 82646, USNM 109709-14,1-2 leagues SSE Tehuantepec, UMMZ 82639-41. Tenango, UIMNH 36209-10.between Tlacolulita and Tequisistlán, CNHM 105125.Yerba Santa, UIMNH 6155-56. Puebla: Atencingo, KU 39626.SkullIn studying the osteology of the genusConophis, I have examined two complete skeletons (oneC. vittatusand oneC. lineatus); two additional skulls ofC. vittatusandC. lineatus; and 24 sets of dentigerous bones, representing all of the species. Terminology of the skeletal elements is that of Duellman (1958), Parker (1878), Radovanovic (1937) and Szunyoghy (1932). The drawing of the right side of the skull of a specimen ofTomodon lineatusthat appears in Jan and Sordelli (1881:liv. 50, pl. 2, fig. 34) is of little value due to its small size and lack of detail.The skull ofConophisis typical of a relatively unspecialized colubrid snake. Skulls ofConophis lineatus concolorandC. vittatusclosely resemble each other. The following description is based primarily on the skull ofC. lineatus concolor(UMMZ S-778).The elements are discussed in the following order: nasal region, cranium and associated elements, maxillo-palatal-pterygoid arch, mandible, dentition, and vertebrae.Nasal region.—The premaxillary is relatively heavy and has a concavity posteroventrally. The lateral processes slope downward, but remain fairly thick, and do not project far laterally. This shape (fig. 6) tends to strengthen the nasal region; this anterior strengthening may be a reflection of the fossorial habits of these snakes. There are no posterior processes of the premaxillary; thus the line of fusion with the nasals and septo-maxillaries is broad. Thenasal plate is more than twice as long as wide. The nasals are relatively flat above, although each curves slightly downward medially and fuses into the medial nasal septum; laterally each nasal is narrower and deflected downward, forming a small dorsal shield over the nasal cavity. The septo-maxillaries are closely associated with the vomers and form the cavity in which the organ of Jacobson is situated. The broad medial part of the septo-maxillary forms the roof and anterior border of the cavity, whereas the anterior part of the vomer contains the main part of the capsule and forms the posterior and most of the lateral borders of the cavity. The vomer has a thin anterior ridge that gradually disappears before it reaches the border of the premaxillary. The vomer is approximately U-shaped, when viewed from below. It has no posterior process and does not articulate with the parasphenoid; there is a sizeable gap between the two bones. The septo-maxillary has a lateral process that terminally is directed slightly anteriorly.Fig. 6.The skull, lacking dentigerous bones, ofConophis lineatus concolor(UMMZ S-788) showing (A) dorsal, (B) lateral, and (C) ventral views. × 3.Cranium and associated elements.—The frontal is almost three times as long as it is wide; it is flat above with an emarginate dorsolateral margin that forms the upper limit of the optic capsule. Ventrally the frontal is concave and forms the median limits of the optic cavity. Farther ventrally the frontal joins with the parasphenoid, which at this place forms the ventral extent of the skull, and together with the basisphenoid forms the ventral part of the posterior three-fourths of the skull. In ventral aspect, the parasphenoid is a long, thin bone, slightly expanded anteriorly. It forms the anterior floor of the optic foramen; whereas the frontal forms the anterior roof of the same opening. The frontal and its septo-maxillary process surround the olfactory fenestra. The prefrontal articulates with the anterolateral process of the frontal. The posterior surface of the prefrontal forms the anterior wall of the orbit of the eye. The articulating surface upon which the median process of the maxillary bone rests is situated ventrally. The anterior dorsal surface of the prefrontal, together with the anterolateral edge of the frontal, extends slightly over the nasal cavity, affording some degree of protection for the contained organs and forming the posterior border of the cavity. A small nasal process also extends anteriorly from the ventrolateral surface of the prefrontal. The orbital-nasalis foramen is located in the anterior surface of the prefrontal. The parietals are fused into one large bone that forms the roof and sides of the middle part of the cranial cavity. From its suture with the frontal, the dorsal surface of the parietal is relatively flat in the area bounded laterally by the parietal crests, which extend posteromedially from the anterolateral corners of the bone and converge medially at a point near its posterior margin. A slight posterior extension of the parietal crests forms the supratemporal crest, which is present on the posterior part of the parietal and on the anterior part of the supraoccipital. The postfrontals are attached to the anterolateral processes of the parietal. Together the anterior surfaces of these two bones form the posterior rim of the orbit of the eye. The postfrontal extends laterally and ventrally and has a terminal extension that projects anterolaterally. In an articulated skull the trans-palatine articulates with the ventrolateral articulating surface of the postfrontal. Anteromedially, the parietal forms the roof and posterior margin of the optic foramen. The basisphenoid, which is fused with the parasphenoid, also forms a small part of the posteroventral margin of the optic foramen. The basisphenoid forms the floor of the middle part of the cranial cavity and the ventromedial down-pouching that contains the pituitary body. Posterolateral to the parietal and dorsal to the posterior part of the basisphenoid is the prootic. Laterally this bone is deeply emarginate; posteriorly it forms a large part of the otic notch, through which the columella passes. The columella is a long, thin bony rod that terminates posteriorly in cartilage. It is the cartilagenous part of the columella that connects with the external sound detecting mechanism. There are several foramina on the lateral surface of the prootic. On the anterolateral surface of the prootic, branches of the trigeminal nerve pass through three foramina whereas the facial nerve passes through the single posterior foramennear the otic notch. The squamosal is attached dorsoventrally to the posterior part of the parietal and to the lateral part of the prootic. At this place of attachment there is on the prootic a relatively heavy crest that forms a rather broad articulating base. The squamosal is long, flat, and curves slightly in a dorsal direction throughout its length; it becomes thinner and narrower posteriorly. The posterior third of the squamosal forms a broad base by means of which the squamosal articulates with the quadrate. The columella and the squamosal extend posteriorly beyond the limits of the braincase. Posteriorly the skull consists of four bones: an unpaired median dorsal supraoccipital, an unpaired median ventral basioccipital and two lateral exoccipitals. The basioccipital does not have noticeable pterygoid processes, but is rather smooth ventrally and only slightly emarginate on its posterolateral margins. Posteriorly, this bone forms the ventral part of the occipital condyle. The rest of the condyle, on each side, is formed by the exoccipitals. The exoccipitals also form part of the base to which the squamosal is attached. The exoccipitals extend around the sides of the foramen magnum and meet dorsally. Each exoccipital also forms the posterior part of the otic notch, which traverses the exoccipital. The exoccipitals bear moderate occipital crests that extendposterolaterally across the supraoccipital as branches from the supratemporal crest. The supraoccipital also has a medial crest that extends a short distance posteriorly from the supratemporal crest onto the exoccipitals at their dorsal line of fusion.Fig. 7.The maxillo-palatal-pterygoid arch ofConophis lineatus concolor(UMMZ S-788) showing (A) dorsal, (B) lateral, and (C) ventral views. × 3. Teeth shown by means of broken lines were represented only by their sockets.Maxillo-palatal-pterygoid arch.—In an articulated skull, the anterior edge of the maxillary is immediately posterior to the lateral tip of the premaxillary (fig. 7). The maxillary is curved moderately laterally and is not robust at its tip, but it becomes heavier about one-third of its length posteriorly. A dorsomedian process begins at about one-third of its distance from the anterior end; the prefrontal articulates with this process. The process is broad and almost flat, except that at its medial end, an elongate, rounded knob extends ventrally. The dorsomedian process of the maxillary extends toward, but does not meet, a lateral process from the palatine. The maxillary teeth are set in sockets on the ventral surface of the bone. Just posterior to the level of the last prediastemal tooth is the median trans-palatine process that articulates with the anteromedian part of the trans-palatine. Immediately posterior to this process, the maxillary narrows slightly; then it broadens to form an obliquely oriented knob. The posteroventral surface of the posterior knob of the maxillary bears one or two enlarged maxillary teeth. (These teeth are discussed further in the section on Dentition.) The anterolateral part of the trans-palatine articulates with the dorsal surface of the posterior knob of the maxillary. Toward the middle of its length, the trans-palatine narrows considerably; then it broadens again and articulates with the pterygoid. The palatine is slightly rounded at its anterior end, which extends anteriorly to the posterior margin of the vacuity containing Jacobson's organ. The palatine extends posteriorly to the trans-palatine process of the maxilla, where the palatine articulates with the pterygoid. A posterior pterygoid process from the palatine projects posteromedially from the end of the palatine and overlaps the anterior end of the pterygoid. Just less than one-half the distance from the anterior end of the palatine, there is a lateral process that curves ventrolaterally forming a blunt tip posteriorly. Slightly more posteriorly and on the medial side of the palatine, is a medial sphenoid process, which is thin, rather broad, and curves ventromedially; ultimately it comes to lie near the anterior part of the parasphenoid. The palatine teeth are set in shallow sockets on the ventral edge of the bone. Of the bones of the maxillo-palatal-pterygoid arch, those on the pterygoid extend farthest posteriorly. The pterygoid is broad medially and posteriorly, although pointed at its posterior tip. The trans-palatine articulates in a broad line at about one-third of the distance along the lateral margin of the pterygoid. Immediately posterior to this articulation, there is a median ridge on the pterygoid; lateral to the pterygoid ridge is an abrupt hollow, the pterygoid groove. Posteromedially, this groove becomes gradually more shallow and disappears. The dorsal surface of the pterygoid is rounded anteriorly and somewhat flattened posteriorly, whereas the ventral surface is gently rounded along its length, except that there is a high median crest. The pterygoid teeth are situated in shallow sockets along this crest. The teeth diminish in size posteriorly.Fig. 8.The left mandible and associated quadrate ofConophis lineatus concolor(UMMZ S-788) showing (A) lateral and (B) medial views. × 3. Teeth shown by means of broken lines were represented only by their sockets.Mandible.—The dentary (fig. 8) is compressed laterally and rounded below. The teeth, which are longest about one-third of the way from the anterior end of the dentary, are set in sockets on the medial side of the bone.The posterior half of the dentary overlies the fused surangular-prearticular part of the articular. Ventrally, the posterior part of the dentary underlies the splenial, which is set in a median trench within the dentary. Near the common suture of the dentary and the splenial is the large inferior alveolar foramen; completely within the splenial and ventral to the inferior alveolar foramen is the anterior mylohyoid foramen. Posterior to the splenial and also forming a part of the ventral surface of the mandible is the wedge-shaped angular, which lies directly beneath the fused surangular-prearticular. As has been implied, the articular, the surangular, and the prearticular are fused. The prearticular part of this bone forms a part of Meckel's canal. In the surangular part, immediately posterior to the end of the dentary, is the large surangular foramen. Lying in a longitudinal axis along the medial surface of the articular is a high crest, dorsal to which is a deep hollow. The lateral wall of the articular above this hollow is thin and rounded dorsally; the ventral surface is uniformly round and slightly curved dorsally, except that it ends with a short tympanic crest, which projects beyond the articulation with the quadrate. Where the quadrate articulates with the dorsolateral surface of the posterior portion of the squamosal, the former is broad and has a high mid-lateral crest, which extends about one-third of the distance down the quadrate before disappearing. The columellar process (the place of fusion of thecolumella) is about two-thirds of the way down the medial surface of the quadrate. Ventrally the quadrate has a narrow neck dorsal to its articulation with the articular. The articulation is formed by two lateral flanges of the quadrate that fit over a medial ridge formed by the articular.DentitionTeeth on the maxillary and pterygoid decrease in size posteriorly, whereas those of the dentary do likewise except for the first one or two that are usually slightly smaller than those immediately posterior. The palatine teeth are subequal in size. The enlarged, grooved teeth on the maxillary are in shallow sockets on the posteroventral surface of the posterior knob of the maxillary. These teeth point posteriorly. The grooves are deep and are situated anterolaterally. One or two enlarged grooved teeth are present on a given maxillary. There seems to be a correlation between the type of preservation, the age of the snake, and the number of grooved teeth. Old (large) individuals always have only one grooved tooth that is rooted and functional, whereas some of the younger animals have two in place. Usually replacement teeth are present in alcoholic specimens, but these unrooted teeth are lost in the preparation of dried skeletons. Thus, it seems that inConophisonly one pair of grooved teeth is functional at any one time, although usually replacement teeth are present behind and beside the functional one. Some specimens have one tooth in the medial socket on one side and one in the lateral socket on the other. Replacement teeth on the maxillary and dentary are present in the buccal tissue on the medial side of the bones, whereas on the palatines and pterygoids, the replacement teeth are present laterally. Apparently there are no significant differences in dentition among the members of the genusConophis.VertebraeThe fiftieth vertebra ofConophis vittatus(UMMZ 82642) can be described as follows: The neural spine is elongate, thin and low; the posterior edge is sharply emarginate, and the anterior edge is only slightly emarginate. The zygosphene is thin dorsoventrally; in a ventral or dorsal view the zygosphene has a slightly concave anterior edge, the flat surface of which is oriented ventrolaterally. The centrum is elongate and triangular from below; it is widest at the paradiapophyses and narrowest at the short condylar neck. The condylus is directed posteriorly. The centrum, when viewed laterally, is slightly concave and has prominent subcentral ridges that extend from the median side of the paradiapophysial articular surfaces posteriorly to the neck of the condylus. The paradiapophysial articular surfaces are well developed and have two facets. The diapophysial surface is larger and more spherical than the parapophysial one. The parapophysial process projects beyond the parapophysial articular surface and is nearly even with the lip of the cotyle, which is slightly oval. The neural arch is slightly depressed; its width is somewhat less than the width of the cotyle. The articular surfaces of the postzygapophyses are oval and are directed posterolaterally. There is a strongly developed concave interzygapophysial ridge. A well-developed accessory spine extends laterally beyond the oval articular facets of the pre-zygapophysis and forms a slightly flattened, blunt spine. Excellent drawingsof the middle thoracic vertebra ofConophis lineatus dunnifrom Honduras were published by Auffenberg (1958:6).HemipenesThe hemipenes ofConophisare moderately caliculate, having spines covering the surface from the base to near the apex (fig. 9). These spines are largest near the base and are reduced to small papillate projections near the apex. The apex terminates in a small disc having three to five laminae inC. vittatusand one lamina inC. lineatus concolor. The sulcus is bifurcate; the fork is near the base and almost gives the appearance of two sulci on some specimens. Distally the apices are widely separated, and the intervening space gives the hemipenis a slightly bilobed appearance in some species (especiallyC. vittatus) or a deeply bilobed appearance in others (especiallyC. lineatus concolor).Fig. 9.The everted left hemipenis of Conophis vittatus (UMMZ 82650). × 5.The everted hemipenis reaches posteriorly to the eighth subcaudal scale. The sulcus bifurcates at the third subcaudal scale. The situation is similarin situ(Cope, 1895:pl. 28, fig. 2).There are no apparent hemipenial differences among the species of the genusConophis. As can be seen in the above description, the hemipenis ofC. vittatusis less bilobed and has a more pronounced disc at the apex than the others. The hemipenis ofC. lineatus concoloris most bilobed, but has the smallest apical disc. The other species and subspecies vary widely within these extremes.Food and FeedingConophiseats mostly small lizards, especiallyCnemidophorus. In MéxicoConophisoccurs in semi-arid habitat whereCnemidophorusis common. A specimen each ofConophis vittatusandC. lineatus lineatuswere obtained while I was collectingCnemidophorus. The only record ofConophishaving fed on a warm-blooded vertebrate was obtained in the course of this study, when I recovered from the stomach of aConophis lineatus concolor(CNHM 36299) from Chichén Itzá, Yucatán, a heteromyid rodent (Heteromys gaumeri).Ralph Axtell (personal communication) observedConophisactively searching for food at dusk. His observations were made near Tehuantepec, Oaxaca, and the snakes were seen to chase lizards of the genusCnemidophorus. Near Alvarado, Veracruz, in the late afternoon, I watched aConophis lineatus lineatusfollow a lizard into a hole.Mittleman (1944:122) presents the only discussion of the mode of feeding of a captive specimen ofConophis lineatusssp. When presented with aThamnophisslightly smaller than itself, theConophisstruck, and within eight minutes immobilized theThamnophis. Within one-half hour theThamnophiswas swallowed. Three days later theConophisate anotherThamnophis, though still distended from its first meal; nine days later it ate aStoreria. In the course of several months, theConophisate various toads and hylids and two moreStoreria. Apparently members of the genusConophisdo not constrict their prey, but rely upon a combination of loss of blood and action of the venom to completely immobilize their prey.Ditmars (1931:pls. 26-27) showed three photographs of "Conophis lineatus" (actuallyConophis pulcher) ingesting another snake, identified by him as a youngOphis (= Xenodon) colubrinus.Effect of PoisonThe rear fangs of these snakes are large for the size of the snake. Various collectors have been bitten, and several reports of the effect of the poison have been published. The snakes are aggressive and bite constantly while being handled. A field companion, Dale L. Hoyt, was bitten on the forefinger by a specimen ofC. l. lineatusand immediately felt a burning sensation. The finger swelled, much as it would if stung by a wasp, but it returned to normal size in about twenty-four hours. Ditmars (1931:legend pl. 27) reported immediate burning pain and a localized swelling, an inch in diameter and half an inch high, which lasted for several hours. Mertens (1952b:83) reported merely that the hand of the gardener at the Instituto Tropical in San Salvador bled strongly for a full hour. Edward H. Taylor was bitten by a specimen ofConophis vittatus(Taylor and Smith, 1939:252); pain and swelling lasted for some time. Taylor (personal communication) is still troubled by damage incurred by that bite, which apparently resulted in mechanical damage to the second joint of the middle finger, for the joint swells when the finger is used or exercised. William E. Duellman (personal communication) was bitten on the hand in July,1956. There was immediate pain and localized swelling, both of which disappeared several hours later.TAXONOMIC RELATIONSHIPS AND EVOLUTIONThe genusConophisis known only from the Recent. Except thatConophisbelongs to the subfamily xenodontinae and probably is of New World origin, little is known about the relationships of the genus. Auffenberg (1958) described a new genus and species of fossil colubrid snake from the Miocene of Montana asDryinoides oxyrhachisand compared it with several recent genera. This specimen, of which there is a relatively complete skull and a series of vertebrae, seems most closely to resemble a specimen ofConophis lineatus dunni(UF 7657) from Honduras, with which it was compared in basic osteology. The two genera could be related, for the progenitors ofConophispossibly inhabited much of North America in the Miocene.Another possibility is that the main stock of the xenodontines reached South America in earliest Tertiary times, and that the formation of the Panamanian and Colombian seaways that separated South America and Central America from the Late Paleocene to the middle of the Pliocene left theConophisstock isolated in Middle America where members of the genus dispersed through semi-arid habitats.Turning our attention now to the species within the genus, instead of the genus as a whole,Conophis vittatusis readily set apart from other members of the genus on the basis of the universal presence of seven supralabials. In basic coloration it also differs, having no stripe on the 1st scale-row, or spots on the venter, and a maximum of four broad stripes on the body. The other species appear to be more closely related; these make up theC. lineatus-group.Conophis nevermannidiffers so much from the other species that it might be placed in a separate group. Nevertheless, the basic striped pattern, which is masked by the increased melanism of many specimens, indicates thatnevermanniis more closely related to thelineatus-group than tovittatus. Thelineatus-group, thus, consists ofpulcher,nevermanniand the three subspecies oflineatus. In this group the color pattern is characterized by the high frequency of ventral spotting, darkening of part of the supralabials, dark pigmentation on the 1st scale-row, and more than four dark stripes on the body of adults.Conophis lineatus concolor, on which the dark pigmentation on the body apparently is secondarily lost, is an exception.If differences in color pattern be used as an indication of the relationships between the species and subspecies of the genusConophis, I would considerC. vittatusthe most divergent unit. The subspecies oflineatusclosely resemble one another and, as a unit, resemblepulcherfrom which they differprimarilyin the position of the dorsalmost stripes.Conophis nevermanniis more divergent than ispulcherfrom the specieslineatus, but probably is not so far removed fromlineatusas isvittatus.In the light of what has been pointed out immediately above with respect to resemblances of, and differences between, the species, an hypothesis to account for their formation and for their presence in the areas where they are today is the following: Concurrent with climatic fluctuations in the Late Pliocene and Pleistocene, the northernmost population differentiated into the speciesvittatus, and has subsequently spread north and west from the region of Tehuantepec, México. During the same periodnevermannibecame isolated in northern Costa Rica.The speciespulcherprobably differentiated from the remaininglineatusstock during the Early Pleistocene orogenic upheaval in Guatemala. Thepulcherstock was isolated on the Pacific Coastal slopes of Guatemala, whilelineatusmoved through the subhumid corridor of northern Middle America into México and southward toward Costa Rica (Stuart, 1954a). In the Late Pleistocene and Recent,pulchermoved back across the central Guatemalan highlands occupying its present range in northern Middle America. Primarily because of the formation of unsuitable habitat (wet forest) that presently separates the geographic ranges of populations oflineatus, this species differentiated into three subspecies.
Remarks.—Smith (1941:121-122) describedC. pulcher plagosusfrom Tonalá, Chiapas, and characterized the subspecies by its having "(1) the ventrals completely unspotted; (2) secondary lines on paravertebral rows not continuous posteriorly; (3) all other lines on body also somewhat spotted in appearance; (4) dusky markings on chin and supralabial border very dim (less distinct than inp. pulcheror any member of thelineatusseries)." Although all Chiapan specimens lack ventral spots, specimens from Guatemala have no spots, small spots, or large spots. Even in specimens from Tegucigalpa, Honduras, the southernmost limit of the range,the spotting varies from a few inconspicuous spots to many large spots. Paravertebral rows were continuous posteriorly in alimens examined by me. Likewise, all other stripes were continuous bands of uniform width posteriorly, having appeared anteriorly as rows of spots or dashes. The amount of brown on the chin and labials has been shown previously not to be geographically significant. The absence of characters of adequate significance to separate populations precludes the naming of subspecies in this species.Mertens (1952a:93, and 1952b:61-62) designated three specimens from El Salvador asC. pulcher plagosus. In the latter paper, Mertens, on the basis of a description of a specimen of "C. lineatus" from Divisadero, El Salvador, given by Schmidt (1928:200), referred that specimen also toC. pulcher plagosus. I have examined this specimen and refer it toC. lineatus dunni. Although I have not seen Merten's specimens, on the basis of the excellent descriptions given by Mertens (1952b:61-62), I refer the three Salvadoranean specimens toC. lineatus dunni.The presence of paravertebral stripes in combination with the characteristics of the genus distinguishConophis pulcherfrom all other snakes in southern México and Central America. The only sympatric species of this genus,C. lineatus dunni, differs in that it lacks paravertebral stripes, although it may have a single vertebral stripe.Conophis lineatus dunnihas lateral dark stripes that are present on the 3rd and 4th scale-rows, never on the anterior third of the body as inC. pulcher. Even in juveniles the third pair of dark stripes includes the lower part of the 9th scale-row inC. pulcher, whereas the dorsal most dark stripe ofC. lineatus dunninever includes more than the lower part of the 8th scale-row.
Remarks.—Smith (1941:121-122) describedC. pulcher plagosusfrom Tonalá, Chiapas, and characterized the subspecies by its having "(1) the ventrals completely unspotted; (2) secondary lines on paravertebral rows not continuous posteriorly; (3) all other lines on body also somewhat spotted in appearance; (4) dusky markings on chin and supralabial border very dim (less distinct than inp. pulcheror any member of thelineatusseries)." Although all Chiapan specimens lack ventral spots, specimens from Guatemala have no spots, small spots, or large spots. Even in specimens from Tegucigalpa, Honduras, the southernmost limit of the range,the spotting varies from a few inconspicuous spots to many large spots. Paravertebral rows were continuous posteriorly in alimens examined by me. Likewise, all other stripes were continuous bands of uniform width posteriorly, having appeared anteriorly as rows of spots or dashes. The amount of brown on the chin and labials has been shown previously not to be geographically significant. The absence of characters of adequate significance to separate populations precludes the naming of subspecies in this species.
Mertens (1952a:93, and 1952b:61-62) designated three specimens from El Salvador asC. pulcher plagosus. In the latter paper, Mertens, on the basis of a description of a specimen of "C. lineatus" from Divisadero, El Salvador, given by Schmidt (1928:200), referred that specimen also toC. pulcher plagosus. I have examined this specimen and refer it toC. lineatus dunni. Although I have not seen Merten's specimens, on the basis of the excellent descriptions given by Mertens (1952b:61-62), I refer the three Salvadoranean specimens toC. lineatus dunni.
The presence of paravertebral stripes in combination with the characteristics of the genus distinguishConophis pulcherfrom all other snakes in southern México and Central America. The only sympatric species of this genus,C. lineatus dunni, differs in that it lacks paravertebral stripes, although it may have a single vertebral stripe.Conophis lineatus dunnihas lateral dark stripes that are present on the 3rd and 4th scale-rows, never on the anterior third of the body as inC. pulcher. Even in juveniles the third pair of dark stripes includes the lower part of the 9th scale-row inC. pulcher, whereas the dorsal most dark stripe ofC. lineatus dunninever includes more than the lower part of the 8th scale-row.
Distribution.—Pacific coastal region of Chiapas, México, southeastward into Guatemala; southeastern highlands and the dry valley of central and eastern Guatemala; Caribbean lowlands of Honduras southward to the region of Tegucigalpa, Honduras (fig. 4).
Specimens examined.—Total of 27, as follows:Guatemala:no specific locality, CNHM 22912, NMW 16830.Jutiapa: Hacienda Mongoy, UMMZ 106725.El Progreso: El Progreso, CAS 67000;El Rancho, UMMZ 106724;San Antonio, CAS 66999. "Peten," USNM 6751(2), 6803.Sacatepequez: Dueñas, BMNH 64.1.26.17, 64.1.26.126-127.Zacapa: Pepesca, AMNH 72555-56.
Honduras:no specific locality, AMNH 58364.Cortes: San Pedro Sula, CNHM 5295-96.Francisco Morazan: El Zamarano, AMNH 70189; Tegucigalpa, MCZ 49785, 49787-88, 49791, 49793, 49795.
México:Chiapas:Soconusco, UIMNH 33646-47; Tonalá, USNM 109707.
Conophis vittatusPeters
Tomodon lineatum(in part), Duméril, Bibron andDuméril,Erpétologie Générale, 7(pt. 2):936-938, February 25, 1854.
Conophis vittatusPeters, Monatsb. Akad. Wiss. Berlin, pp. 519-520, pl.,fig. 3, October, 1860; Cope, Proc. Amer. Philos. Soc., 11:162, 1870; BocourtinDuméril, Bocourt and Mocquard, Mission Scientifique au Mexique et dans l'Amerique Centrale, 2:644-646, pl. 38, fig. 7, 1886; Günther, Biologia Centrali-Americana, p. 165, March, 1895; Boulenger, Catalogue of the Snakes in the British Museum (Natural History), 3:123-124, 1896; Cope, Amer. Nat., 30:1024, 1896; Ann. Rept. U. S. Natl. Mus. for 1898, pp. 1094-1095, 1232, 1900; Gadow, Proc. Zool. Soc. London, 2:225, 1905; Amaral, Mem. Inst. Butantan, 4:211, 1929; Gadow, Jorullo, p. 55, 1930; Smith, Zool. Ser. Field Mus. Nat. Hist., 24:31-32, January 30, 1939; Taylor and Smith, Univ. Kansas Sci. Bull., 25:252-253, pl. 23, July 10, 1939; Stuart, Contr. Lab. Vert. Biol. Univ. Michigan, 65:23, March, 1954; Alvarez del Toro, Reptiles de Chiapas, pp. 153-154, 1960.
Conophis lineatusCope, Proc. Acad. Nat. Sci. Philadelphia, 16(3):167, 1864 [necDuméril, Bibron and Duméril,Erpétologie Générale, 7(pt. 2):936-938, atlas, pl. 73, February 25, 1854; specimen from Colima]; Sumichrast, Arch. Sci. Nat., p. 246, 1873.
Tomodon vittatus, Bocourt, Journ. de Zool., p. 407, 1876.
Conophis sumichrasti sumichrastiCope, Journ. Acad. Nat. Sci. Philadelphia, ser. 2, 8:137, 1876 (Types.—United States National Museum, nos. 29123, 30258; type locality.—Tehuantepec, México); Bull. U. S. Natl. Mus., 32:77, 1887; Smith and Taylor, Univ. Kansas Sci. Bull., 33(pt. 2):334, March 20, 1950; Maldonado-Koerdell, Inst. Mexicanos Recursos Nat. Renov., p. 124, 1953.
Conophis sumichrasti viduusCope, Journ. Acad. Nat. Sci., Philadelphia, ser. 2, 8:137, 1876 (Type.—United States National Museum, no. 30259; type locality.—Tehuantepec, México); Bull. U. S. Natl. Mus., 32:77, 1887; Cochran, Bull. U. S. Natl. Mus., 220:167, 1961.
Conophis sumichrasti, Cope, Proc. Amer. Philos. Soc., 18:271, August 11, 1879; Sumichrast, Bull. Soc. Zool. France, p. 182, 1880; Cope, Trans. Amer. Philos. Soc., 18:194, April 15, 1895; Cochran, Bull. U. S. Natl. Mus., 220:167, 1961.
Tachymenis lineata(in part), Garman, Mem. Mus. Comp. Zool., 8:60-61, July, 1884.
Conophis vittatus sumichrasti, Cope, Ann. Rept. U. S. Natl. Mus. for 1898, p. 1095, 1900.
Conophis vittatus vidensCope, Ann. Rept. U. S. Natl. Mus., for 1898, p. 1095, 1900 (apparentlapusforviduus).
Conophis vittatus vittatus, Cope, Ann. Rept. U. S. Natl. Mus. for 1898, p. 1095, 1900; Smith, Journ. Washington Acad. Sci., 31:119-120, March 15, 1941; Proc. U. S. Natl. Mus., 92:395, November 5, 1942; Proc. U. S. Natl. Mus., 93:408, October 29, 1943; Ann. Carnegie Mus., 30:91, November 2, 1944; Smith and Taylor, Bull. U. S. Natl. Mus., 187:44, October 5, 1945; Smith, Rev. Soc. Mexicanos Hist. Nat., 7:71, December, 1946; Smith and Taylor, Univ. Kansas Sci. Bull., 33(pt. 2):331, March 20, 1950; Davis and Smith, Herpetologica, 8:134, January 30, 1953; Maldonado-Koerdell, Inst. Mexicanos Recursos Nat. Renov., p. 130, 1953; Peters, Occas. Papers Mus. Zool. Univ. Michigan, 554:22, June 23, 1954; Duellman, Occas. Papers Mus. Zool. Univ. Michigan, 560:15, October 22, 1954; Webb and Fugler, Herpetologica, 13:35, March 30, 1957; Duellman, Occas. Papers Mus. Zool. Univ. Michigan, 589:15, March 21, 1958; Zweifel, Amer. Mus. Novitates, 1949:2, 5, June 17, 1959; Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 15(1):91-92, December 20, 1961.
Conophis vittata, Gadow, Proc. Zool. Soc. London, 2:196, 1905; Through Southern Mexico, p. 181, 1908.
Conophis viduus, Smith, Zool. Ser. Field Mus. Nat. Hist., 24:31, January 30, 1939; Hartweg and Oliver, Misc. Publ. Mus. Zool. Univ. Michigan, 47:26-27, July 13, 1940.
Conophis vittatus viduus, Smith, Journ. Washington Acad. Sci., 31:120-121, March 15, 1941; Proc. U. S. Natl. Mus., 92:395, November 5, 1942; Proc. U. S. Natl. Mus., 93:408, October 29, 1943; Woodbury and Woodbury, Journ. Washington Acad. Sci., 34(11):370, 1944; Smith and Taylor, Proc. U. S. Natl. Mus., 187:44, October 5, 1945; Univ. Kansas Sci. Bull., 33(pt. 2):340, March 20, 1950; Werler and Smith, Texas Journ. Sci., 4:565, fig. 16, December 30, 1952; Maldonado-Koerdell, Inst. Mexicanos Recursos Nat. Renov., p. 130, 1953; Davis and Dixon, Proc. Biol. Soc. Washington, 72:82-83, July 24, 1959.
Conophis vittatus vittatus×Conophis vittatus viduus, Alvarez del Toro and Smith, Herpetologica, 12:13, March 6, 1956.
Type.—Zoologisches Museum Berlin. Type locality not given, for the specimen was purchased from a dealer in Hamburg. The type locality was first restricted to "Acapulco," Guerrero, by Smith (1941:119), then to Laguna Coyuca, Guerrero, México, by Smith and Taylor (1950:331).
Diagnosis.—Three or four dorsal dark stripes, each involving two or more adjacent scale-rows; never having brown or black on the 1st scale-row; seven supralabials immaculate white or pale tannish-white.
Variation.—One hundred seventy-one specimens have 149 to 181 (163.7 ± 6.33) ventrals. One hundred fifty-three of these having complete tails have 55 to 76 (64.8 ± 4.90) subcaudals; the number of ventrals plus subcaudals varies from 214 to 245 (228.5). In 170 specimens the reduction from 19 to 17 dorsal scales takes place between ventrals 84 and 118 (102.3 ± 6.60). Sexual dimorphism is evident in the number of subcaudals; 58 females have 55 to 66 (60.0) and 95 males have 59 to 76 (67.8) subcaudals. The longest specimen (AMNH 68004) is a male from Escurano, Oaxaca, México, having a body length of 668 mm., a tail length of 182 mm. and a total length of850mm. A juvenile (CNHM 40435) fromTehuantepec, Oaxaca, México, has a body length of 133 mm., a tail length of 31 mm. and a total length of 164 mm.
Variation in coloration is of such magnitude that it has been used as the basis for recognition of subspecies. Unfortunately, until this time, most specimens reported upon in the literature represented the two extremes of variation. After examining the coloration of 174 specimens with respect to geographic distribution, I conclude that only one highly variable species is represented. Specimens from the northern and western parts of the range (Michoacán, Colima, and Durango) have the color pattern ofC. vittatusas described by Peters (1860:518-521); these snakes have four narrow black stripes on a white or pale tan background, and an immaculate white venter. The lateral dark stripe, which on the head passes through the eye, is present on the dorsal half of the 3rd and the ventral half of the 4th scale-rows; the dorsolateral dark stripe, which passes along the middle of the head and splits on the nape, is present on the middle of the 8th scale-row. The other extreme in color pattern consists of three broad stripes; the two dorsolateral stripes are fused. This pattern is prevalent in specimens from the area around Tehuantepec, Oaxaca. The lateral stripes include the dorsal half to two-thirds of the 2nd, all of the 3rd and 4th, and half of the 5th scale-rows; the fused dorsolateral stripes sometimes cover all of the area dorsal to and including the dorsal third of the 7th scale-row.
Snakes from areas between Tehuantepec and the margins of the distributionof this species are variously intermediate between the extremes described above. In some snakes from these areas the lateral stripes are broad and include either the dorsal half of the 2nd scale-row or the ventral half of the 5th scale-row, but not both on the same specimen. Also, the dorsolateral stripes are broad and include most of the 9th and a part of the 10th scale-rows. Many specimens from the area around Tehuantepec, where the three-striped pattern is prevalent, have an intermediate pattern. Some have white on the center of the 10th scale-row or lateral stripes that are not so broad as to include the 3rd and 4th and half of each of the 2nd and 5th scale-rows.
The supralabials are immaculate white or pale tan, except that in some specimens the dorsalmost part of some supralabials are dark brown or black as they are included in the ventral boundary of the dark stripe that passes through the eye. There are no dusky markings on the chin or on any of the ventral scales.
There is no ontogenetic change in color pattern; juveniles have the same coloration as adults from the same geographic area.
Color in life is not greatly different from that of preserved specimens. One specimen (UMMZ 114483) from 10.8 miles south ofOaxaca,had in life black stripes, a pale yellowish tan dorsal ground-color and a pale off-white venter.
An excellent photograph of this species appears in Schmidt and Inger (1957:230) under the nameConophis lineatus.
Remarks.—I have been unable to find variation of geographic importance in scutellation in this species. A wide range of variation in the characters of scutellation is present in specimens from most localities; it shows no significant clinal or geographic trends. As I have stated previously, in the discussion of variation, coloration has been the feature primarily used by previous workers to distinguish two "subspecies" for this species;C. vittatus vittatushaving four black stripes andC. vittatus viduushaving three black stripes. Most of the three-striped snakes occur in the vicinity of Tehuantepec, Oaxaca, whereas the four-striped snakes are found near the margins of the range of the species in Durango, Colima, Michoacán, Morelos and Puebla. Specimens that would have to be considered intergrades between the "subspecies" are found in Michoacán, Guerrero, Oaxaca and Chiapas. At the time the subspecies were proposed only specimens from Tehuantepec or from marginal areas were known. Utilizing the large number of specimens of this species presently available, geographic variation is found to be clinal, from those with three stripes from near Tehuantepec, through several intermediate patterns present on specimens from single localities in Guerrero, Oaxaca and Chiapas, to those with four dark stripes in areas farthest removed to the north and west from Tehuantepec. Since only coloration shows geographic variation, and since this variation represents a continuous cline, subspecies cannot be recognized for this species.The presence and position of the three or four dark stripes on the body and the absence of brown on the 1st scale-row or on the ventral scales, in combination with the generic characters, distinguishConophis vittatusfrom all other Méxican snakes. The only other snake that occurs in western México that has been confused withC. vittatusisConiophanes piceivittus taylori, which has 25, instead of 19, scale-rows.
Remarks.—I have been unable to find variation of geographic importance in scutellation in this species. A wide range of variation in the characters of scutellation is present in specimens from most localities; it shows no significant clinal or geographic trends. As I have stated previously, in the discussion of variation, coloration has been the feature primarily used by previous workers to distinguish two "subspecies" for this species;C. vittatus vittatushaving four black stripes andC. vittatus viduushaving three black stripes. Most of the three-striped snakes occur in the vicinity of Tehuantepec, Oaxaca, whereas the four-striped snakes are found near the margins of the range of the species in Durango, Colima, Michoacán, Morelos and Puebla. Specimens that would have to be considered intergrades between the "subspecies" are found in Michoacán, Guerrero, Oaxaca and Chiapas. At the time the subspecies were proposed only specimens from Tehuantepec or from marginal areas were known. Utilizing the large number of specimens of this species presently available, geographic variation is found to be clinal, from those with three stripes from near Tehuantepec, through several intermediate patterns present on specimens from single localities in Guerrero, Oaxaca and Chiapas, to those with four dark stripes in areas farthest removed to the north and west from Tehuantepec. Since only coloration shows geographic variation, and since this variation represents a continuous cline, subspecies cannot be recognized for this species.
The presence and position of the three or four dark stripes on the body and the absence of brown on the 1st scale-row or on the ventral scales, in combination with the generic characters, distinguishConophis vittatusfrom all other Méxican snakes. The only other snake that occurs in western México that has been confused withC. vittatusisConiophanes piceivittus taylori, which has 25, instead of 19, scale-rows.
Distribution.—Semi-arid habitats on Pacific slopes from extreme southern Durango southeastward to Tuxtla Gutierrez, Chiapas, and inland in the eastern Balsas Basin to Morelos and western Puebla (fig. 5).
Fig. 5.Selected locality records forConophis vittatus.
Fig. 5.Selected locality records forConophis vittatus.
Specimens examined.—Total of 174, as follows:México:no specific locality, AMNH 66150-52, SU 9465.Chiapas: Piedra Parada, USNM 121453.Pizo de Oro, UIMNH 40821. Tuxtla Gutierrez, Parque Madero, UIMNH 37992-93, 38036-37.Colima: no specific locality, MCZ 46860, USNM 31394, 31396-97. 1 mi. SW Colima, AMNH 12783. S of Manzanillo, AMNH 19641.Durango: Hacienda de Gabriel, AMNH 14217.Guerrero: Acahuizotla, TCWC 7419, 9469.1 mi. W Acahuizotla, TCWC 7418. 3 mi. W Acapulco, AMNH 71626.6 mi. E Acapulco, TCWC 9476-77.10 mi. S Acapulco, TCWC 8578.Agua del Obispo, CNHM 104948, TCWC 11586. near Chilpancingo, MVZ 45067, UMMZ 85722-23.1 mi. SW Colotlipa, TCWC 9471-74.2 mi. SW Colotlipa, TCWC 9475. 14 mi. S Ixtapán de la Sal, KU 67648.Laguna Coyuca, CNHM 25881, UMMZ 80942. near La Unión, AMNH 66337.Magueyes, Laguna Coyuca, AMNH 66149.Playa Encantada, TCWC 9470. 1 mi. S Tierra Colorada, KU 67649. nearXaltinanguis, km. 405, CNHM 104947.Michoacán: Coalcomán, UMMZ 104693.1/2 mi. SE Coalcomán, UMMZ 104492.1 mi. N. Coalcomán, UMMZ 112543.1 mi. NE Coalcomán, UMMZ 104692. Puerta de la Playa, UMMZ 105155. 12 mi. STzitzio (by road), UMMZ 99153.Morelos: 12 km. NW Axochiapan, TCWC 7311, UIMNH 17613, 25924. 7 mi. SE Cuernavaca, MVZ 32258.Huajintlán, km. 133, CNHM 103270. 12 km. S Puente de Ixtla, km. 133, CNHM 104949.Oaxaca: Bisiliana, AMNH 68010.near Caoba, foot of Cerro Arenal, AMNH 68009.Cerro Arenal, AMNH 68000-03.Cerro de Laollaga, UIMNH 36213.Cerro de San Pedro, UIMNH 17616.Cerro Palma de Oro, UIMNH 37116. "C. Madrena, Sto. T. Quieri," UIMNH 46904. near Chivela, MCZ 25021. Cinco Cerros, UIMNH 37114.Dami Liesa, AMNH 66877, UIMNH 6158, 37115.Escuranos, AMNH 66873-74, 68004-06.Finca Santa Teresa, 2 km. NW Tehuantepec, UMMZ 82648.Huilotepec, AMNH 66878, UIMNH 40820.between Huilotepec and Tehuantepec, AMNH 65106, UMMZ 82644-45.Las Tejas, UIMNH 6151-54.Mixtequilla, UIMNH 6157, 36211.between Mixtequilla Mountains and Tehuantepec, UMMZ 82652.between Niltepec and "Carixxal,"AMNH 68876. 10.8 mi. SE Oaxaca, UMMZ 114483.Quiengola, UIMNH 17617.between Quiengola Mountains and Tehuantepec, UMMZ 82647.Rancho Poso Río, 6 km. S Tehuantepec, UIMNH 6144-49, 37117-19, UMMZ 82649-51.Rincón Bamba, CNHM 105129-30, UIMNH 17615.Salazar, AMNH 66875.vicinity of Salina Cruz, UMMZ 82653.San Gerónimo, AMNH 4306, CNHM 1457.San Lucas Ixtepec, UIMNH 36206. San Juan Lajarcia, UIMNH 36212. San Mateo del Mar, AMNH 65914.San Pablo, UIMNH 36207.Santa María (Cerro de Liesa), AMNH 68011. Tapanatepec, MCZ 27806-11. Tehuantepec, AMNH 19644, 65107-09, 65907-13 plus 7, 66871-72, 66879, 68007-08, CNHM 40435-36, 105126-28, MCZ 46403, UIMNH 6150, 17614, 17618, 29692, 36208, 37120-21, UMMZ 82642-43, 82646, USNM 109709-14,1-2 leagues SSE Tehuantepec, UMMZ 82639-41. Tenango, UIMNH 36209-10.between Tlacolulita and Tequisistlán, CNHM 105125.Yerba Santa, UIMNH 6155-56. Puebla: Atencingo, KU 39626.
Skull
In studying the osteology of the genusConophis, I have examined two complete skeletons (oneC. vittatusand oneC. lineatus); two additional skulls ofC. vittatusandC. lineatus; and 24 sets of dentigerous bones, representing all of the species. Terminology of the skeletal elements is that of Duellman (1958), Parker (1878), Radovanovic (1937) and Szunyoghy (1932). The drawing of the right side of the skull of a specimen ofTomodon lineatusthat appears in Jan and Sordelli (1881:liv. 50, pl. 2, fig. 34) is of little value due to its small size and lack of detail.
The skull ofConophisis typical of a relatively unspecialized colubrid snake. Skulls ofConophis lineatus concolorandC. vittatusclosely resemble each other. The following description is based primarily on the skull ofC. lineatus concolor(UMMZ S-778).
The elements are discussed in the following order: nasal region, cranium and associated elements, maxillo-palatal-pterygoid arch, mandible, dentition, and vertebrae.
Nasal region.—The premaxillary is relatively heavy and has a concavity posteroventrally. The lateral processes slope downward, but remain fairly thick, and do not project far laterally. This shape (fig. 6) tends to strengthen the nasal region; this anterior strengthening may be a reflection of the fossorial habits of these snakes. There are no posterior processes of the premaxillary; thus the line of fusion with the nasals and septo-maxillaries is broad. Thenasal plate is more than twice as long as wide. The nasals are relatively flat above, although each curves slightly downward medially and fuses into the medial nasal septum; laterally each nasal is narrower and deflected downward, forming a small dorsal shield over the nasal cavity. The septo-maxillaries are closely associated with the vomers and form the cavity in which the organ of Jacobson is situated. The broad medial part of the septo-maxillary forms the roof and anterior border of the cavity, whereas the anterior part of the vomer contains the main part of the capsule and forms the posterior and most of the lateral borders of the cavity. The vomer has a thin anterior ridge that gradually disappears before it reaches the border of the premaxillary. The vomer is approximately U-shaped, when viewed from below. It has no posterior process and does not articulate with the parasphenoid; there is a sizeable gap between the two bones. The septo-maxillary has a lateral process that terminally is directed slightly anteriorly.
Fig. 6.The skull, lacking dentigerous bones, ofConophis lineatus concolor(UMMZ S-788) showing (A) dorsal, (B) lateral, and (C) ventral views. × 3.
Fig. 6.The skull, lacking dentigerous bones, ofConophis lineatus concolor(UMMZ S-788) showing (A) dorsal, (B) lateral, and (C) ventral views. × 3.
Cranium and associated elements.—The frontal is almost three times as long as it is wide; it is flat above with an emarginate dorsolateral margin that forms the upper limit of the optic capsule. Ventrally the frontal is concave and forms the median limits of the optic cavity. Farther ventrally the frontal joins with the parasphenoid, which at this place forms the ventral extent of the skull, and together with the basisphenoid forms the ventral part of the posterior three-fourths of the skull. In ventral aspect, the parasphenoid is a long, thin bone, slightly expanded anteriorly. It forms the anterior floor of the optic foramen; whereas the frontal forms the anterior roof of the same opening. The frontal and its septo-maxillary process surround the olfactory fenestra. The prefrontal articulates with the anterolateral process of the frontal. The posterior surface of the prefrontal forms the anterior wall of the orbit of the eye. The articulating surface upon which the median process of the maxillary bone rests is situated ventrally. The anterior dorsal surface of the prefrontal, together with the anterolateral edge of the frontal, extends slightly over the nasal cavity, affording some degree of protection for the contained organs and forming the posterior border of the cavity. A small nasal process also extends anteriorly from the ventrolateral surface of the prefrontal. The orbital-nasalis foramen is located in the anterior surface of the prefrontal. The parietals are fused into one large bone that forms the roof and sides of the middle part of the cranial cavity. From its suture with the frontal, the dorsal surface of the parietal is relatively flat in the area bounded laterally by the parietal crests, which extend posteromedially from the anterolateral corners of the bone and converge medially at a point near its posterior margin. A slight posterior extension of the parietal crests forms the supratemporal crest, which is present on the posterior part of the parietal and on the anterior part of the supraoccipital. The postfrontals are attached to the anterolateral processes of the parietal. Together the anterior surfaces of these two bones form the posterior rim of the orbit of the eye. The postfrontal extends laterally and ventrally and has a terminal extension that projects anterolaterally. In an articulated skull the trans-palatine articulates with the ventrolateral articulating surface of the postfrontal. Anteromedially, the parietal forms the roof and posterior margin of the optic foramen. The basisphenoid, which is fused with the parasphenoid, also forms a small part of the posteroventral margin of the optic foramen. The basisphenoid forms the floor of the middle part of the cranial cavity and the ventromedial down-pouching that contains the pituitary body. Posterolateral to the parietal and dorsal to the posterior part of the basisphenoid is the prootic. Laterally this bone is deeply emarginate; posteriorly it forms a large part of the otic notch, through which the columella passes. The columella is a long, thin bony rod that terminates posteriorly in cartilage. It is the cartilagenous part of the columella that connects with the external sound detecting mechanism. There are several foramina on the lateral surface of the prootic. On the anterolateral surface of the prootic, branches of the trigeminal nerve pass through three foramina whereas the facial nerve passes through the single posterior foramennear the otic notch. The squamosal is attached dorsoventrally to the posterior part of the parietal and to the lateral part of the prootic. At this place of attachment there is on the prootic a relatively heavy crest that forms a rather broad articulating base. The squamosal is long, flat, and curves slightly in a dorsal direction throughout its length; it becomes thinner and narrower posteriorly. The posterior third of the squamosal forms a broad base by means of which the squamosal articulates with the quadrate. The columella and the squamosal extend posteriorly beyond the limits of the braincase. Posteriorly the skull consists of four bones: an unpaired median dorsal supraoccipital, an unpaired median ventral basioccipital and two lateral exoccipitals. The basioccipital does not have noticeable pterygoid processes, but is rather smooth ventrally and only slightly emarginate on its posterolateral margins. Posteriorly, this bone forms the ventral part of the occipital condyle. The rest of the condyle, on each side, is formed by the exoccipitals. The exoccipitals also form part of the base to which the squamosal is attached. The exoccipitals extend around the sides of the foramen magnum and meet dorsally. Each exoccipital also forms the posterior part of the otic notch, which traverses the exoccipital. The exoccipitals bear moderate occipital crests that extendposterolaterally across the supraoccipital as branches from the supratemporal crest. The supraoccipital also has a medial crest that extends a short distance posteriorly from the supratemporal crest onto the exoccipitals at their dorsal line of fusion.
Fig. 7.The maxillo-palatal-pterygoid arch ofConophis lineatus concolor(UMMZ S-788) showing (A) dorsal, (B) lateral, and (C) ventral views. × 3. Teeth shown by means of broken lines were represented only by their sockets.
Fig. 7.The maxillo-palatal-pterygoid arch ofConophis lineatus concolor(UMMZ S-788) showing (A) dorsal, (B) lateral, and (C) ventral views. × 3. Teeth shown by means of broken lines were represented only by their sockets.
Maxillo-palatal-pterygoid arch.—In an articulated skull, the anterior edge of the maxillary is immediately posterior to the lateral tip of the premaxillary (fig. 7). The maxillary is curved moderately laterally and is not robust at its tip, but it becomes heavier about one-third of its length posteriorly. A dorsomedian process begins at about one-third of its distance from the anterior end; the prefrontal articulates with this process. The process is broad and almost flat, except that at its medial end, an elongate, rounded knob extends ventrally. The dorsomedian process of the maxillary extends toward, but does not meet, a lateral process from the palatine. The maxillary teeth are set in sockets on the ventral surface of the bone. Just posterior to the level of the last prediastemal tooth is the median trans-palatine process that articulates with the anteromedian part of the trans-palatine. Immediately posterior to this process, the maxillary narrows slightly; then it broadens to form an obliquely oriented knob. The posteroventral surface of the posterior knob of the maxillary bears one or two enlarged maxillary teeth. (These teeth are discussed further in the section on Dentition.) The anterolateral part of the trans-palatine articulates with the dorsal surface of the posterior knob of the maxillary. Toward the middle of its length, the trans-palatine narrows considerably; then it broadens again and articulates with the pterygoid. The palatine is slightly rounded at its anterior end, which extends anteriorly to the posterior margin of the vacuity containing Jacobson's organ. The palatine extends posteriorly to the trans-palatine process of the maxilla, where the palatine articulates with the pterygoid. A posterior pterygoid process from the palatine projects posteromedially from the end of the palatine and overlaps the anterior end of the pterygoid. Just less than one-half the distance from the anterior end of the palatine, there is a lateral process that curves ventrolaterally forming a blunt tip posteriorly. Slightly more posteriorly and on the medial side of the palatine, is a medial sphenoid process, which is thin, rather broad, and curves ventromedially; ultimately it comes to lie near the anterior part of the parasphenoid. The palatine teeth are set in shallow sockets on the ventral edge of the bone. Of the bones of the maxillo-palatal-pterygoid arch, those on the pterygoid extend farthest posteriorly. The pterygoid is broad medially and posteriorly, although pointed at its posterior tip. The trans-palatine articulates in a broad line at about one-third of the distance along the lateral margin of the pterygoid. Immediately posterior to this articulation, there is a median ridge on the pterygoid; lateral to the pterygoid ridge is an abrupt hollow, the pterygoid groove. Posteromedially, this groove becomes gradually more shallow and disappears. The dorsal surface of the pterygoid is rounded anteriorly and somewhat flattened posteriorly, whereas the ventral surface is gently rounded along its length, except that there is a high median crest. The pterygoid teeth are situated in shallow sockets along this crest. The teeth diminish in size posteriorly.
Fig. 8.The left mandible and associated quadrate ofConophis lineatus concolor(UMMZ S-788) showing (A) lateral and (B) medial views. × 3. Teeth shown by means of broken lines were represented only by their sockets.
Fig. 8.The left mandible and associated quadrate ofConophis lineatus concolor(UMMZ S-788) showing (A) lateral and (B) medial views. × 3. Teeth shown by means of broken lines were represented only by their sockets.
Mandible.—The dentary (fig. 8) is compressed laterally and rounded below. The teeth, which are longest about one-third of the way from the anterior end of the dentary, are set in sockets on the medial side of the bone.The posterior half of the dentary overlies the fused surangular-prearticular part of the articular. Ventrally, the posterior part of the dentary underlies the splenial, which is set in a median trench within the dentary. Near the common suture of the dentary and the splenial is the large inferior alveolar foramen; completely within the splenial and ventral to the inferior alveolar foramen is the anterior mylohyoid foramen. Posterior to the splenial and also forming a part of the ventral surface of the mandible is the wedge-shaped angular, which lies directly beneath the fused surangular-prearticular. As has been implied, the articular, the surangular, and the prearticular are fused. The prearticular part of this bone forms a part of Meckel's canal. In the surangular part, immediately posterior to the end of the dentary, is the large surangular foramen. Lying in a longitudinal axis along the medial surface of the articular is a high crest, dorsal to which is a deep hollow. The lateral wall of the articular above this hollow is thin and rounded dorsally; the ventral surface is uniformly round and slightly curved dorsally, except that it ends with a short tympanic crest, which projects beyond the articulation with the quadrate. Where the quadrate articulates with the dorsolateral surface of the posterior portion of the squamosal, the former is broad and has a high mid-lateral crest, which extends about one-third of the distance down the quadrate before disappearing. The columellar process (the place of fusion of thecolumella) is about two-thirds of the way down the medial surface of the quadrate. Ventrally the quadrate has a narrow neck dorsal to its articulation with the articular. The articulation is formed by two lateral flanges of the quadrate that fit over a medial ridge formed by the articular.
Dentition
Teeth on the maxillary and pterygoid decrease in size posteriorly, whereas those of the dentary do likewise except for the first one or two that are usually slightly smaller than those immediately posterior. The palatine teeth are subequal in size. The enlarged, grooved teeth on the maxillary are in shallow sockets on the posteroventral surface of the posterior knob of the maxillary. These teeth point posteriorly. The grooves are deep and are situated anterolaterally. One or two enlarged grooved teeth are present on a given maxillary. There seems to be a correlation between the type of preservation, the age of the snake, and the number of grooved teeth. Old (large) individuals always have only one grooved tooth that is rooted and functional, whereas some of the younger animals have two in place. Usually replacement teeth are present in alcoholic specimens, but these unrooted teeth are lost in the preparation of dried skeletons. Thus, it seems that inConophisonly one pair of grooved teeth is functional at any one time, although usually replacement teeth are present behind and beside the functional one. Some specimens have one tooth in the medial socket on one side and one in the lateral socket on the other. Replacement teeth on the maxillary and dentary are present in the buccal tissue on the medial side of the bones, whereas on the palatines and pterygoids, the replacement teeth are present laterally. Apparently there are no significant differences in dentition among the members of the genusConophis.
Vertebrae
The fiftieth vertebra ofConophis vittatus(UMMZ 82642) can be described as follows: The neural spine is elongate, thin and low; the posterior edge is sharply emarginate, and the anterior edge is only slightly emarginate. The zygosphene is thin dorsoventrally; in a ventral or dorsal view the zygosphene has a slightly concave anterior edge, the flat surface of which is oriented ventrolaterally. The centrum is elongate and triangular from below; it is widest at the paradiapophyses and narrowest at the short condylar neck. The condylus is directed posteriorly. The centrum, when viewed laterally, is slightly concave and has prominent subcentral ridges that extend from the median side of the paradiapophysial articular surfaces posteriorly to the neck of the condylus. The paradiapophysial articular surfaces are well developed and have two facets. The diapophysial surface is larger and more spherical than the parapophysial one. The parapophysial process projects beyond the parapophysial articular surface and is nearly even with the lip of the cotyle, which is slightly oval. The neural arch is slightly depressed; its width is somewhat less than the width of the cotyle. The articular surfaces of the postzygapophyses are oval and are directed posterolaterally. There is a strongly developed concave interzygapophysial ridge. A well-developed accessory spine extends laterally beyond the oval articular facets of the pre-zygapophysis and forms a slightly flattened, blunt spine. Excellent drawingsof the middle thoracic vertebra ofConophis lineatus dunnifrom Honduras were published by Auffenberg (1958:6).
Hemipenes
The hemipenes ofConophisare moderately caliculate, having spines covering the surface from the base to near the apex (fig. 9). These spines are largest near the base and are reduced to small papillate projections near the apex. The apex terminates in a small disc having three to five laminae inC. vittatusand one lamina inC. lineatus concolor. The sulcus is bifurcate; the fork is near the base and almost gives the appearance of two sulci on some specimens. Distally the apices are widely separated, and the intervening space gives the hemipenis a slightly bilobed appearance in some species (especiallyC. vittatus) or a deeply bilobed appearance in others (especiallyC. lineatus concolor).
Fig. 9.The everted left hemipenis of Conophis vittatus (UMMZ 82650). × 5.
Fig. 9.The everted left hemipenis of Conophis vittatus (UMMZ 82650). × 5.
The everted hemipenis reaches posteriorly to the eighth subcaudal scale. The sulcus bifurcates at the third subcaudal scale. The situation is similarin situ(Cope, 1895:pl. 28, fig. 2).
There are no apparent hemipenial differences among the species of the genusConophis. As can be seen in the above description, the hemipenis ofC. vittatusis less bilobed and has a more pronounced disc at the apex than the others. The hemipenis ofC. lineatus concoloris most bilobed, but has the smallest apical disc. The other species and subspecies vary widely within these extremes.
Food and Feeding
Conophiseats mostly small lizards, especiallyCnemidophorus. In MéxicoConophisoccurs in semi-arid habitat whereCnemidophorusis common. A specimen each ofConophis vittatusandC. lineatus lineatuswere obtained while I was collectingCnemidophorus. The only record ofConophishaving fed on a warm-blooded vertebrate was obtained in the course of this study, when I recovered from the stomach of aConophis lineatus concolor(CNHM 36299) from Chichén Itzá, Yucatán, a heteromyid rodent (Heteromys gaumeri).
Ralph Axtell (personal communication) observedConophisactively searching for food at dusk. His observations were made near Tehuantepec, Oaxaca, and the snakes were seen to chase lizards of the genusCnemidophorus. Near Alvarado, Veracruz, in the late afternoon, I watched aConophis lineatus lineatusfollow a lizard into a hole.
Mittleman (1944:122) presents the only discussion of the mode of feeding of a captive specimen ofConophis lineatusssp. When presented with aThamnophisslightly smaller than itself, theConophisstruck, and within eight minutes immobilized theThamnophis. Within one-half hour theThamnophiswas swallowed. Three days later theConophisate anotherThamnophis, though still distended from its first meal; nine days later it ate aStoreria. In the course of several months, theConophisate various toads and hylids and two moreStoreria. Apparently members of the genusConophisdo not constrict their prey, but rely upon a combination of loss of blood and action of the venom to completely immobilize their prey.
Ditmars (1931:pls. 26-27) showed three photographs of "Conophis lineatus" (actuallyConophis pulcher) ingesting another snake, identified by him as a youngOphis (= Xenodon) colubrinus.
Effect of Poison
The rear fangs of these snakes are large for the size of the snake. Various collectors have been bitten, and several reports of the effect of the poison have been published. The snakes are aggressive and bite constantly while being handled. A field companion, Dale L. Hoyt, was bitten on the forefinger by a specimen ofC. l. lineatusand immediately felt a burning sensation. The finger swelled, much as it would if stung by a wasp, but it returned to normal size in about twenty-four hours. Ditmars (1931:legend pl. 27) reported immediate burning pain and a localized swelling, an inch in diameter and half an inch high, which lasted for several hours. Mertens (1952b:83) reported merely that the hand of the gardener at the Instituto Tropical in San Salvador bled strongly for a full hour. Edward H. Taylor was bitten by a specimen ofConophis vittatus(Taylor and Smith, 1939:252); pain and swelling lasted for some time. Taylor (personal communication) is still troubled by damage incurred by that bite, which apparently resulted in mechanical damage to the second joint of the middle finger, for the joint swells when the finger is used or exercised. William E. Duellman (personal communication) was bitten on the hand in July,1956. There was immediate pain and localized swelling, both of which disappeared several hours later.
TAXONOMIC RELATIONSHIPS AND EVOLUTION
The genusConophisis known only from the Recent. Except thatConophisbelongs to the subfamily xenodontinae and probably is of New World origin, little is known about the relationships of the genus. Auffenberg (1958) described a new genus and species of fossil colubrid snake from the Miocene of Montana asDryinoides oxyrhachisand compared it with several recent genera. This specimen, of which there is a relatively complete skull and a series of vertebrae, seems most closely to resemble a specimen ofConophis lineatus dunni(UF 7657) from Honduras, with which it was compared in basic osteology. The two genera could be related, for the progenitors ofConophispossibly inhabited much of North America in the Miocene.
Another possibility is that the main stock of the xenodontines reached South America in earliest Tertiary times, and that the formation of the Panamanian and Colombian seaways that separated South America and Central America from the Late Paleocene to the middle of the Pliocene left theConophisstock isolated in Middle America where members of the genus dispersed through semi-arid habitats.
Turning our attention now to the species within the genus, instead of the genus as a whole,Conophis vittatusis readily set apart from other members of the genus on the basis of the universal presence of seven supralabials. In basic coloration it also differs, having no stripe on the 1st scale-row, or spots on the venter, and a maximum of four broad stripes on the body. The other species appear to be more closely related; these make up theC. lineatus-group.Conophis nevermannidiffers so much from the other species that it might be placed in a separate group. Nevertheless, the basic striped pattern, which is masked by the increased melanism of many specimens, indicates thatnevermanniis more closely related to thelineatus-group than tovittatus. Thelineatus-group, thus, consists ofpulcher,nevermanniand the three subspecies oflineatus. In this group the color pattern is characterized by the high frequency of ventral spotting, darkening of part of the supralabials, dark pigmentation on the 1st scale-row, and more than four dark stripes on the body of adults.Conophis lineatus concolor, on which the dark pigmentation on the body apparently is secondarily lost, is an exception.
If differences in color pattern be used as an indication of the relationships between the species and subspecies of the genusConophis, I would considerC. vittatusthe most divergent unit. The subspecies oflineatusclosely resemble one another and, as a unit, resemblepulcherfrom which they differprimarilyin the position of the dorsalmost stripes.Conophis nevermanniis more divergent than ispulcherfrom the specieslineatus, but probably is not so far removed fromlineatusas isvittatus.
In the light of what has been pointed out immediately above with respect to resemblances of, and differences between, the species, an hypothesis to account for their formation and for their presence in the areas where they are today is the following: Concurrent with climatic fluctuations in the Late Pliocene and Pleistocene, the northernmost population differentiated into the speciesvittatus, and has subsequently spread north and west from the region of Tehuantepec, México. During the same periodnevermannibecame isolated in northern Costa Rica.
The speciespulcherprobably differentiated from the remaininglineatusstock during the Early Pleistocene orogenic upheaval in Guatemala. Thepulcherstock was isolated on the Pacific Coastal slopes of Guatemala, whilelineatusmoved through the subhumid corridor of northern Middle America into México and southward toward Costa Rica (Stuart, 1954a). In the Late Pleistocene and Recent,pulchermoved back across the central Guatemalan highlands occupying its present range in northern Middle America. Primarily because of the formation of unsuitable habitat (wet forest) that presently separates the geographic ranges of populations oflineatus, this species differentiated into three subspecies.