. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. SKELETON. 55 reduced or even disappear, those remaining being connected by a one or two-jointed copula. The chondrocranium of the larval ANURA (Rana, fig. 86) differs considerably from that of other amphibia as well as from the adult conditions. Like all amphib- ians it is platybasic. The pterygoquadrate has, besides the normal otic and epipterygoid processes, a cranio-quadrate process connected with the nasal region, in front of which is the articulation of the lower jaw. In front of the cornua are a pair of s
. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. SKELETON. 55 reduced or even disappear, those remaining being connected by a one or two-jointed copula. The chondrocranium of the larval ANURA (Rana, fig. 86) differs considerably from that of other amphibia as well as from the adult conditions. Like all amphib- ians it is platybasic. The pterygoquadrate has, besides the normal otic and epipterygoid processes, a cranio-quadrate process connected with the nasal region, in front of which is the articulation of the lower jaw. In front of the cornua are a pair of suprarostral cartilages and a similar pair of infrarostrals lie in front of the. exf FIG. 86.—Chondrocranium of tadpole of Rana before the metamorphosis; after Gaupp. c.,ant, anterior canal; els, superior labial cartilage; ctr, cornu trabeculae; car, foramen for carotid; ext. c, external canal; fe, ethmoid fenestra; m, Meckel's cartilage; pc, posterior canal; po, otic process of quadrate; pr. as.' ascending process of quadrate; q, quad- rate; tm, tectum medialis; ttm, taenia tecti marginalis; tsyn, tectum svnoticum; I—V, nerves and nerve exits. Meckelian, from which they are apparently derived. These four rostrals form a ring around the suctorial mouth and recall the labial cartilages of the elasmobranchs and the annular cartilage of the cyclostome mouth. At the time of metamorphosis the changes are great, and as the result is more like the chondrocranium of other amphibia, the larval condition must be regarded as adaptive rather than ancestral. The suprarostrals disappear and the jaw shifts the hinge back to the normal position, this being accompanied by the elon- gation of Meckel's cartilage, an absorption of the ascending process and a folding of the pterygoquadrate bar. At the same time a pterygoid grows out in front to join an antorbital process from the cranium. A stapes develops and connects. Please note that these images are extracted from scanned page images that ma
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