File:The dinosaur book - the ruling reptiles and their relatives (1951) (19777733854).jpg

Title: The dinosaur book : the ruling reptiles and their relatives
Identifier: bookruli00colb (find matches)
Year: 1951 (1950s)
Authors: Colbert, Edwin H. (Edwin Harris), 1905-2001; Knight, Charles Robert, 1874-1953; American Museum of Natural History
Subjects: Dinosaurs; Reptiles, Fossil
Publisher: New York : Published for the American Museum of Natural History by McGraw-Hill
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: IMLS / LSTA / METRO

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It was probably the development of this egg that marked the first divergence of the early reptiles from the amphibians, for just as certain fish were the progenitors of the amphibians, so were certain amphibians the progenitors of the reptiles. And the basic reptiliarT grandparents were labyrintho- donts. Therefore, while the thesis of laby- rinthodont extinction before the onslaught of their reptilian competitors is valid, it is in a wav equally valid to say that one branch of the labyrinthodont line was con- tinued by the reptiles because certain early labyrinthodonts were transformed into reptiles. The first reptiles had great evolutionary The "grandfather" of the reptiles: Sey- mouria. This animal formed an almost per- fect intermediate link between the early am- phibians and the ensuing reptiles, and repre- s^>§ents the structural ancestral type from which all the reptiles evolved Restoration by F. L. Juiiuc?
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potentialities. They were free of the water. They could venture over the face of the earth and continue their kind in regions where the less efficient amphibians could not survive. Thus was born a mighty race. The earliest reptiles were very much like their amphibian ancestors. In fact, some of the most primitive reptiles were so very am- phibian-like that there has been a great deal of argument as to whether these basic rep- tiles might not more properly be regarded as advanced amphibians. So it goes. The more we know about the classification of animals, the less distinct become the lines of demarcation separating one form from another or one group from another. In other words, we find the intermediate stages which prove the validity of evolution. Certainly there could hardlv be an ani- mal more exactly intermediate in its anatomical features between the amphibi- ans and the reptiles than the Permian genus, Seymouria (see-MOOR-e-ya), from the rocks known as the redbedsof Texas. This animal approximates structurally the stem for all reptilian life; it is the "grand- father reptile." The reptiles may be classified in a broad, general way on the basis of skull design, as follows: a. Anapsida (an-APS-i-da) Skull roof solid, without any openings be- hind the eye. b. Synapsida (sine-APS-i-da) Skull roof perforated by a lower opening behind the eye bounded above by the postorbital and squamosal bones, c. Parapsida (par-APS-i-da) Skull roof perforated by an upper opening behind the eye, bounded below by the post- 48

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