SUMMARY

Fig. 10.Fig. 10. Leiopelma hochstetteri larva, lateral and ventral (after Stephenson, 1955), ×4.

Stephenson (1955) showed that embryos ofL. hochstetteridevelop equally well on land (in damp places) or in the water, and that embryos prematurely released from egg capsules develop successfully in the water. The larvae possess both pairs of legs (Fig. 10) and a broad gular foldsimilar to that of larval salamanders. InL. hochstetterithe fold grows back over the forelegs temporarily, but remains free from the body and presently the legs reappear, whereas inL. archeyithe forelegs are not covered at any time. No branchial chamber or spiracle is formed. Of course direct development, without a tadpole, occurs in several other groups of Anura, but in each case terrestrial adaptations are obvious. This is not true ofLeiopelma, which Stephenson regards as more nearly comparable with Urodela in its development than with other Anura, and he sees in it a "primary and amphibious" mode instead of a terrestrial specialization.

TheAscaphustadpole bears no outward resemblance to the larva ofLeiopelma, but is a normal tadpole in form, although sluggish in activity. Its greatly expanded labial folds bear numerous rows of horny epidermal "teeth," which, with the lips, serve to anchor the tadpole to stones in the swift water of mountain brooks. Noble (1927) noticed that particles of food were taken in through the external nares, and that a current of water passed through these openings and out by way of the median spiracle. It appears that any action by the teeth and jaws in scraping algae from the rocks (which were bare in the stream where I have collectedAscaphus) would be quite incidental, and that the lips and teeth must be primarily a clinging mechanism. Certain other mountain brook tadpoles (for example,Borborocoetes) show similar devices, but these are developed independently, as specializations from the usual sort of tadpole.

May it not be that closure of the gill-chamber by the opercular (=gular) fold, retardation of limb development, expansion of the lips, growth of parallel rows of horny teeth, and other correlated features that make a tadpole, were brought about as an adaptation of the primitive Anuran larva to a swift-stream habitat, and that this "basic patent" then later served to admit the tadpoles of descendant types to an alga-scraping habit in quiet water as well? The tadpole, as a unique larval type among vertebrates, bears the hallmarks of an abrupt adaptive shift, such as might have occurred within the limits of a single family, and it seems difficult to imagine the enclosed branchial chamber, the tooth-rows, and lips of a familiar tadpole as having evolved without some kind of suctorial function along the way.

The Anura probably originated among temnospondylous labyrinthodonts, through a line represented approximately byEugyrinus,Amphibamus, and the Triassic frogProtobatrachus, as shown by Watson, Piveteau and others. The known Paleozoic lepospondyls do not show clear indications of a relationship with Urodela, butLysorophusmay well be on the ancestral stem of the Apoda.

Between Urodela and Anura there are numerous resemblances which seem to indicate direct relationship through a common stock: (1) a similar reduction of dermal bones of the skull and expansion of palatal vacuities; (2) movable basipterygoid articulation in primitive members of both orders; (3) an operculum formed in the otic capsule, with opercularis muscle; (4) many details of cranial development, cranial muscles, and thigh muscles, especially betweenAscaphusand the Urodela, as shown by Pusey and Noble; (5) essentially similar manner of vertebral development, quite consistent with derivation of both orders from Temnospondyli; (6) presence in the larva ofLeiopelmaof a salamander-like gular fold, four limbs, and no suggestion of modification from a tadpole (Stephenson).

Broom, R.

1918. Observations on the genusLysorophusCope. Ann. Mag. Nat. Hist., (9)2:232-239.

Bystrow, A. P.

1938. Dvinosaurus als neotenische Form der Stegocephalen. Acta Zool., 19:209-295.

Case, E. C.

1935. Description of a collection of associated skeletons ofTrimerorhachis. Contrib. Mus. Pal. Univ. Michigan, 4:227-274.

Cope, E. D.

1889. The Batrachia of North America. Bull. U. S. Nat. Mus., 34:1-525.

de Beer, G. R.

1937. The development of the vertebrate skull. Pp. xxiii + 552. Oxford, Clarendon Press.

de Villiers, C. G. S.

1934. Studies of the cranial anatomy ofAscaphus trueiStejneger, the American "Liopelmid." Bull. Mus. Comp. Zool., 77:1-38.

Emelianov, S. W.

1936. Die Morphologie der Tetrapodenrippen. Zool. Jahrb. (Anat.), 62:173-274.

Francis, E. T. B.

1934. The anatomy of the salamander. Pp. xxxi + 381. Oxford, Clarendon Press.

Gamble, D. L.

1922. The morphology of the ribs and the transverse processes ofNecturus maculatus. Jour. Morph., 36:537-566.

Gray, P.

1930. On the attachments of the Urodele rib to the vertebra and their homologies with the capitulum and tuberculum of the Amniote rib. Proc. Zool. Soc. London, 1930(1931):907-911.

Gregory, J. T.

1950. Tetrapods from the Pennsylvanian nodules from Mazon Creek, Illinois. Am. Jour. Sci., 248:833-873.

Hecht, M. E.

1957. A case of parallel evolution in salamanders. Proc. Zool. Soc. Calcutta, Mookerjee Mem.:283-292.

Holmgren, N.

1933. On the origin of the tetrapod limb. Acta Zool., 14:185-295.1939. Contributions to the question of the origin of the tetrapod limb. Acta Zool., 20:89-124.1949a. Contributions to the question of the origin of tetrapods. Acta Zool., 30:459-484.1949b. On the tetrapod limb problem again. Acta Zool., 30:485-508.

1933. On the origin of the tetrapod limb. Acta Zool., 14:185-295.

1939. Contributions to the question of the origin of the tetrapod limb. Acta Zool., 20:89-124.

1949a. Contributions to the question of the origin of tetrapods. Acta Zool., 30:459-484.

1949b. On the tetrapod limb problem again. Acta Zool., 30:485-508.

Herre, W.

1935. Die Schwanzlurche der mitteleocänen (oberlutetischen) Braunkohle des Geiseltales und die Phylogenie der Urodelen unter Einschluss der fossilen Formen. Zoologica, 33:87, 1-5.

Jarvik, E.

1942. On the structure of the snout of Crossopterygians and lower gnathostomes in general. Zool. Bidrag fran Upsala, 21:235-675. 1952. On the fish-like tail in the Ichthyostegid Stegocephalians. Meddelelser on Grønland, 114(12):1-90.

Mookerjee, H.K.

1930a. On the development of the vertebral column of the Urodela. Phil. Trans. Roy. Soc. London, B 218:415-446.1930b. On the development of the vertebral column of the Anura. Philos. Trans. Royal Soc. London, B 219:165-196.

1930a. On the development of the vertebral column of the Urodela. Phil. Trans. Roy. Soc. London, B 218:415-446.

1930b. On the development of the vertebral column of the Anura. Philos. Trans. Royal Soc. London, B 219:165-196.

MacBride, E.W.

1932. Recent work on the development of the vertebral column. Cambridge, Biol. Rev., 7:108-148.

McDowell, S.B.

1958. Are the frogs specialized seymouriamorphs? (Abstract) Anat. Rec., 132(3):472.

Naef, A.

1929. Notizen zur Morphologie und Stammesgeschichte der Wirbeltiere. 15. Dreissig Thesen über Wirbelsäule und Rippen, insbesondere bei den Tetrapoden. Zool. Jahrb., 50:581-600.

Noble, G. K.

1922. The phylogeny of the Salientia; I. The osteology and the thigh musculature; their bearing on classification and phylogeny. Bull. Amer. Mus. Nat. Hist., 46:1-87.1927. The value of life-history data in the study of the evolution of the Amphibia. Annals New York Acad. Sci., 30:31-128.

1922. The phylogeny of the Salientia; I. The osteology and the thigh musculature; their bearing on classification and phylogeny. Bull. Amer. Mus. Nat. Hist., 46:1-87.

1927. The value of life-history data in the study of the evolution of the Amphibia. Annals New York Acad. Sci., 30:31-128.

Piveteau, J.

1937. Un Amphibien du Trias inférieur. Essai sur l'origine et l'évolution des Amphibiens Anoures. Annales de Paléontologie, 26:135-176.1955. Anoura. In: Traité de Paléontologie, 5:250-274. J. Piveteau, Masson et Cie, Paris.

1937. Un Amphibien du Trias inférieur. Essai sur l'origine et l'évolution des Amphibiens Anoures. Annales de Paléontologie, 26:135-176.

1955. Anoura. In: Traité de Paléontologie, 5:250-274. J. Piveteau, Masson et Cie, Paris.

Pusey, H. K.

1943. On the head of the liopelmid frog,Ascaphus truei. I. The chondrocranium, jaws, arches, and muscles of a partly grown larva. Quart. Jour. Micr. Sci., 84:105-185.

Reed, H. D.

1915. The sound-transmitting apparatus in Necturus. Anat. Rec., 9:581-590.

Remane, A.

1936. Wirbelsäule und ihre Abkömmlinge. In: Handbuch der vergleichenden Anatomie der Wirbeltiere, L. Bolket al., 4:1-206. Urban and Schwarzenberg, Berlin, Vienna.

Ritland, R. M.

1955a. Studies on the post-cranial morphology of Ascaphus truei. I. Skeleton and spinal nerves. Jour. Morph., 97:119-174.1955b. Studies on the post-cranial morphology of Ascaphus truei. II. Myology. Jour. Morph., 97:215-282.

1955a. Studies on the post-cranial morphology of Ascaphus truei. I. Skeleton and spinal nerves. Jour. Morph., 97:119-174.

1955b. Studies on the post-cranial morphology of Ascaphus truei. II. Myology. Jour. Morph., 97:215-282.

Romer, A. S.

1945. Vertebrate paleontology. 2nd edition. Pp. viii + 687. Univ. Chicago Press.1947. Review of the Labyrinthodontia. Bull. Mus. Comp. Zool., 99:3-368.

1945. Vertebrate paleontology. 2nd edition. Pp. viii + 687. Univ. Chicago Press.

1947. Review of the Labyrinthodontia. Bull. Mus. Comp. Zool., 99:3-368.

Säve-Söderbergh, G.

1934. Some points of view concerning the evolution of the vertebrates and the classification of this group. Arkiv för Zoologi, 26A:1-20.

Stadtmüller, F.

1936. Kranium und Visceralskelett der Stegocephalen und Amphibien. In: Handbuch der vergleichenden Anatomie der Wirbeltiere, by L. Bolket al., 4:501-698.

Stephenson, N. G.

1955. On the development of the frog,Leiopelma hochstetteriFitzinger. Proc. Zool. Soc. London, 124(4):785-795.

Stipanicic, P. N.andReig, O. A.

1955. Breve noticia sobre el hallazgo de anuros en el denominado "Complejo Porfirico de la Patagonia Extraandina," con consideraciones acerca de la composicion geologica del mismo. Revista de la Asoc. Geol. Argentina, 10(4):215-233.1956. El "complejo porfirico de la Patagonia extraandina" y su fauna de Anuros. Acta Geol. Lilloana (Univ. Nac. del Tucuman), 1:185-297.

1956. El "complejo porfirico de la Patagonia extraandina" y su fauna de Anuros. Acta Geol. Lilloana (Univ. Nac. del Tucuman), 1:185-297.

Sushkin, P. P.

1936. Notes on the pro-Jurassic Tetrapoda from U. S. S. R. III. Dvinosaurus Amalitzky, a perennibranchiate stegocephalian from the Upper Permian of North Dvina. Trav. Inst. Pal. Acad. Sci. URSS, 5:43-91.

Watson, D. M. S.

1940. The origin of frogs. Trans. Roy. Soc. Edinburgh, 40(7):195-231.

Transmitted April 7, 1959.

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