File:The chordates (1950) (20618085901).jpg

Title: The chordates
Identifier: chordates00rand (find matches)
Year: 1950 (1950s)
Authors: Rand, Herbert W. (Herbert Wilbur), 1872-1960
Subjects: Chordata
Publisher: Philadelphia : Blakiston
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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Sauropsida: Class Reptilia 467 The general contour of the reptilian body is less streamlined than that of typical aquatic anamniotes. A cervical region, at most only faintly suggested in anamniotes, is distinctly differentiated in reptiles, and in some, notably turtles, becomes much elongated. Gill-chambers, with the intervening gill-arches and internal gills, require much space. The absence of gills in the reptile permits of considerable narrowing of the region just behind the head and, further, important functional advantage is gained by the narrowing and elongating of the neck region. A fish, to change the direction of the line of vision, must rotate the whole body. It is of obvious advantage that the mobile neck of the land animal enables it to "look around" without changing its position and to look backward while running forward. Most modern reptiles have relatively long tails. The very long tail of the chameleon is pre- hensile and may be coiled around a twig to assist the lizard in holding on to its perch in a tree. In some lizards, and in turtles and tortoises, the tails are short. The paired appendages are somewhat more strongly developed than in amphibians, although in living reptiles they are short and in many cases incapable of lifting the body off the ground. Among extinct reptiles, however, were some dinosaurs whose long and strongly built legs indicate capacity for swift running. In the "ostrich dinosaurs" the short forelegs and the long, powerful hindlegs suggest a habit of bipedal locomotion (Fig. 360). In some reptiles legs are rudimentary or totally
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Fin. 360. Struthiomimus, an ostrich-like Cretaceous dinosaur, about 5 feet in height. (Courtesy, \merican Museum of Natural History, New York.)

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