File:The dinosaur book - the ruling reptiles and their relatives (1951) (20374153986).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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position that is strengthened by the fact that these reptiles are found in stream de- posits together with the remains of fishes. Such was Ophiacodon (o-fee-A-ko-don)./ Certain pelycosaurs evolved tremen- douslv long spines on the vertebrae, spines which in life must have supported a mem- branous sail that ran down the middle of the back. These were the sphenacodonts or finbacks, typified by the jrgnus Dimetrodoii. (dye-MET-ro-don), a good-sized reptile, six or seven feet in length. Dimetrodon had a deep skull, armed with many cruel, dagger- like teeth. The sail on the back was tall, thrusting up two or three feet above the line of the backbone. What was the purpose of this huge sail, seemingly so cumbersome, and certainly a serious drain upon the blood supply and the energy of the animal? Much thought and discussion has been given to this problem, with suggestions ranging from the not-so- sublime to the downright ridiculous. Ac- cording to one idea, the long spines on the vertebrae of Dimetrodon afforded a pro- tection for the spinal column—^protection against the attacks of savage enemies. The only thing wrong with this theory is that there were no other large, active carnivo- rous reptiles at that time to prey upon Dimetrodon. Dimetrodon was the lord of his small universe, he was one of the largest and certainly one of the most active and predaceous of the animals living in Texas during Permian times. Another idea had it that the "sail" of Dimetrodon really was a sail, that this animal ventured out onto the surface of the Permian lakes and rivers, scudding along before the wind, tacking back and forth in a fashion approved in the best yachting circles. Such a theory is, of course, one on the ridiculous side. Perhaps the truth is that the sail of Dimetrodon is not to be explained upon any functional grounds. It may very well be that this represents an unbalanced growth, This grotesque "sail" has been a subject of much conjecture. Probably it is merely a case of hereditary maladjustment. In this Permian scene of over 200 million years ago, Edaphosaurus is fleeing from his flesh-eating relative Dimetrodon (in the background). Both were about five or six feet long Restoration by John C. Germana
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