The chordates (1950) (20618184931)


The chordates (1950) (20618184931)



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

Text Appearing Before Image:
Sauropsida: Class Aves =5S 539
Text Appearing After Image:
Fig. 417. Fossilized bones and feathers of Archueopleryx, as they appear on a slab of limestone. Above the slab is shown a partial reconstruction of the distal part of the wing, and below is represented the foot. (Courtesy, Zittel: "Handbuch der Palaeontologie," Munich. R. Oldenbourg.) and tapered gradually to the tip of the tail as in a lizard—there was no terminal pygostyle. So far as can be ascertained, the vertebrae were amphicoelous (as in Sphenodon). The ribs lack uncinate processes, but the animal may have had cartilaginous uncinates which did not fos- silize. The sternum, very poorly preserved, was probably small and without a carina. Abdominal ribs (gastralia) were present (as in Sphenodon and Crocodilia). The skeleton of the limbs is more reptilian than avian, especially that of the forelimb, which has three strongly developed digits, each terminating in a long, pointed claw. The three metacarpals are not fused to one another nor to the carpals—that is, there is no carpo-metacarpus as in modern birds. The skeletons show no signs of pneumaticity of bones. These two skeletons so closely resemble numerous fossil reptilian skeletons (being especially similar to those of certain small dinosaurs) that they would not arouse great interest but for the fact that the fossils not only prove the existence of feathers but to a large extent show the relations of the feathers to regions of the body. The feathers were large and, apparently, structurally similar to the quill-feathers of modern birds. The fossils clearly show well-developed primary and secondary remiges attached to the hand and forearm respectively, as in modern birds. The long tail carried numerous rectrices arranged in a single row along each side of it. They were symmetrically placed, possibly each vertebra supporting a pair. Their axes sloped sharply





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