. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. VERTEBRAL COLUMN. 45 the sacrum even a greater number may be included (cp. the chapter on the pelvis, p. 9(3) : thus in the common Duck (Anas boschas), seven become united with the pelvis, eight remain free, and the pygostyle is composed of ten separately ossified and fused segments, making in all twenty-five vertebras originally present in the caudal region of this Bird. In Archseopteryx the pelvis was much shorter than in existing Birds, and much fewer vertebrae were united with it. Moreover,
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. VERTEBRAL COLUMN. 45 the sacrum even a greater number may be included (cp. the chapter on the pelvis, p. 9(3) : thus in the common Duck (Anas boschas), seven become united with the pelvis, eight remain free, and the pygostyle is composed of ten separately ossified and fused segments, making in all twenty-five vertebras originally present in the caudal region of this Bird. In Archseopteryx the pelvis was much shorter than in existing Birds, and much fewer vertebrae were united with it. Moreover, in embryos of an Australian parrot (Psittacus undu- latus) more vertebrae are formed in the embryo than are seen in the adult. The original type is well preserved to the present day in. FIG. 34.—PELVIS OF OWL (Strixbubo). (Ventral view.) W, position of the primary sacral vertebra?: between 11 and //, and behind IV, are seen the secondary sacral vertebras, fused with the primary ; 11, ilium; Is, isehium; P, pubis; t, foramen between ilium and pubis; JK, last pair of ribs. the Ratitae, in which the posterior caudal vertebrae remain free, instead of uniting to form a pygostyle, and the secondary sacral vertebrae remain longer distinct. Thus the chasm between Archaeopteryx and existing Birds is in this respect essentially lessened. The arches always become united into a single mass with the corresponding centra, and are no longer separated from them for life by sutures, as seen in Crocodiles, and exceptionally in Chelo- nians. The same may be said of the atlas and axis, in which also no sutures persist between the different parts. In the cervical region, where by means of saddle-shaped articulations the vertebras are able to move easily on one another, the bifurcated transverse. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resembl
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