Produced by Chris Curnow, Charlene Taylor, Joseph Cooper and the Online Distributed Proofreading Team at http://www.pgdp.net University of Kansas Publications Museum of Natural History Volume 12, No. 2, pp. 155-180, 10 figs. -----------July 10, 1959--------------- The Ancestry of Modern Amphibia: A Review of the Evidence BY THEODORE H. EATON, JR. University of Kansas Lawrence 1959 University of Kansas Publications, Museum of Natural History Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Robert W. Wilson Volume 12, No. 2, pp. 155-180 Published July 10, 1959 University of Kansas Lawrence, Kansas PRINTED IN THE STATE PRINTING PLANT TOPEKA, KANSAS 1959 [Illustration] 27-8362 [Transcriber's Notes: Several typos have been regulated. One typo of "ancester" for "ancestor" was corrected. One instance of "salamanderlike" corrected to "salamaner-like".] The Ancestry of Modern Amphibia: A Review of the Evidence BY THEODORE H. EATON, JR. INTRODUCTION In trying to determine the ancestral relationships of modern orders of Amphibia it is not possible to select satisfactory structural ancestors among a wealth of fossils, since very few of the known fossils could even be considered possible, and scarcely any are satisfactory, for such a selection. The nearest approach thus far to a solution of the problem in this manner has been made with reference to the Anura. Watson's paper (1940), with certain modifications made necessary by Gregory (1950), provides the paleontological evidence so far available on the origin of frogs. It shows that several features of the skeleton of frogs, such as the enlargement of the interpterygoid spaces and orbits, reduction of the more posterior dermal bones of the skull, and downward spread of the neural arches lateral to the notochord, were already apparent in the Pennsylvanian _Amphibamus_ (Fig. 1), with which Gregory synonymized _Miobatrachus_ and _Mazonerpeton_. But between the Pennsylvanian and the Triassic (the age of the earliest known frog, _Protobatrachus_) there was a great lapse of time, and that which passed between any conceivable Paleozoic ancestor of Urodela and the earliest satisfactory representative of this order (in the Cretaceous) was much longer still. The Apoda, so far as known, have no fossil record.