12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 39 



presently known have a postminimus. The nature of the vertebrae of 

 Eosauravus would indicate that its affinities probably lie with the cap- 

 torhinomorphs. No pelycosaur is presently known to possess vertebrae 

 of a pure cotylosaur type such as is evident in Eosauravus. In view 

 of the primitive pattern of the tarsus, a position near the base of the 

 captorhinomorphs is indicated. 



Establishment of a true reptile of captorhinomorph affinities deep 

 in the Middle Pennsylvanian helps to clear away some of the uncer- 

 tainty surrounding the time of origin of reptiles. The varied reptiles 

 found in the Upper Pennsylvanian of Kansas (Peabody, 1954) and 

 more fragmentary remains from elsewhere indicate that the evolution 

 of pelycosaurs and captorhinomorphs (if petrolacosaurs be considered 

 an offshoot of the captorhinomorphs as suggested by Vaughn, 1955, 

 p. 446) was well advanced. Eosauravus appears to have been at an 

 evolutionary stage which could be ancestral to any known later reptile. 



The particular adaptations of Eosauravus to life in a coal swamp 

 are difficult to assess. Moodie (1909, p. 12) suggests that the reptile 

 was aquatic or semi-aquatic mainly on the basis of an "expanded 

 foot" similar to the broad foot of the obviously aquatic mesosaurs. 

 However, the foot of Eosauravus and the rest of the preserved skele- 

 ton have little to suggest even semi-aquatic habits, but do allow the 

 possibility that this small reptile spent most of its time in the "upper 

 story" of the coal forest at Linton. 



REFERENCES 

 Case, E. C. 



191 1. A revision of the Cotylosauria of North America. Carnegie Inst. 

 Washington Publ. 145, pp. 1-122, 52 figs., 14 pis. 

 Cope, E. D. 



1874. Supplement to the extinct Batrachia and Reptilia of North America. 

 I. Catalogue of the air-breathing Vertebrata from the Coal-measures 

 of Linton, Ohio. Trans. Amer. Philos. Soc, vol. 15, pp. 261-278. 



1896. The Paleozoic reptilian order Cotylosauria. Amer. Nat., 1896, pp. 301- 



304, 1 pi. 



1897. On new Paleozoic Vertebrata from Illinois, Ohio and Pennsylvania. 



Proc. Amer. Philos. Soc, vol. 36, pp. 71-91, 3 pis. 

 Gregory, J. T. 



1950. Tetrapods of the Pennsylvanian nodules from Mazon Creek, Illinois. 

 Amer. Journ. Sci., vol. 248, pp. 833-873, 11 figs. 

 Gregory, J. T., Peabody, F. E., and Price, L. I. 



1956. Revision of the Gymnarthridae, American Permian microsaurs. Pea- 

 body Mus. Nat. Hist., Bull. 10, pp. 1-77, 33 figs., 1 pi. 

 Holmgren, Nils. 



1933- On the origin of the tetrapod limb. Acta Zool., Stockholm, vol. 14, 

 pp. 185-295, 106 figs. 



