File:The dinosaur book - the ruling reptiles and their relatives (1951) (20374144146).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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Labidosaurus Seymourta From "grandfather" Seytnouria, two general lines of reptiles descended. In one, the ani- mals remained small, like Labidosaurus. In the other, there was a tendency to giantism, as may be seen in Diadectes from North America and in the large pariasaurs from the Old World, one of which is shown opposite Restorations by John C. Germann an inheritance from the solid, bony skulls of their labyrinthodont ancestors. Of these anapsids, the first to appear were reptiles belonging to the order known as the Co- tylosauria (ko-TiLE=oj:sawr-^-y_a)• The sey- mouriamorphs, typified by Seytnouria, are perhaps the primitive ancestors of the coty- losaurs. Some authorities have included the seymouriamorphs among the labyrinthodont amphibians rather than among the primitive reptiles. The cotylosaurs evolved through Permian and Triassic times and then became extinct. / \ Their evolution was divided along two lines of development. There was a line of small Permian cotylosaurs, showing certain specializations, known as the labidosaurs (LAB-i-do-sawrs) or eaptorhinomorphs_(kap- +o^RTNE>o-morfs). In contrast the other group of cotylosaurs, known as the diadecto- morphs (dye-a-DEKT-o-morfs), consisted of quite large reptiles living in the Permian period, and small, highlv specialized sur- vivors persisting through the Triassic period. Labidosaurus was small, like Seytnouria. It had the long body and the sprawling, weak limbs of the primitive reptile. The skull, as in all anapsids, was roofed over by solid bone, and was abruptly truncated be- hind. A characteristic feature of this animal was the overhung, or hooked upper jaw. Diadectes (dye-a-DEKT-eez) was a rather large Permian reptile, some five or six feet in length. The legs were sprawling, as in the other primitive anapsids, so that this animal must have been rather clumsy when walking. Diadectes seemingly was a plant- eating reptile, for the teeth were blunt and peglike, and not at all suited to catching animals as were the pointed, spikelike teeth of Seytnouria and Labidosaurus. A remark- able feature of Diadectes was the large pineal opening on the top of the skull, showing that this reptile had a very large "pineal eye"—an organ sensitive to light, which still persists in a much reduced form in the recent lizards and the tuatara (Sphenodon) of New Zealand. Closely related to the American diadectids were the Permian pariasaurs (par-EYE-a-sawrs) of South Africa and Russia. These were really massive reptiles, as big as small cattle. Like the other large cotylosaurs they were seemingly plant eaters, large, heavy, and sluggish. They had 50

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