. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. 212 COMPARATIVE MORPHOLOGY OF VERTEBRATES. In a few mammals only one dentition has been retained (monophyodont); among these may be mentioned the monotremes, sirenians and cetacea. In the marsupial Myrrecobius, where the permanent dentition is greatly reduced, and in some of the insectivores and rodents, a prelacteal dentition has been observed in the embryo, while Rose has described traces of a prelacteal and a post-permanent dentition in man. In a number of mammals (guinea pigs, many bats, etc.) the milk dent
. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. 212 COMPARATIVE MORPHOLOGY OF VERTEBRATES. In a few mammals only one dentition has been retained (monophyodont); among these may be mentioned the monotremes, sirenians and cetacea. In the marsupial Myrrecobius, where the permanent dentition is greatly reduced, and in some of the insectivores and rodents, a prelacteal dentition has been observed in the embryo, while Rose has described traces of a prelacteal and a post-permanent dentition in man. In a number of mammals (guinea pigs, many bats, etc.) the milk dentition is lost before FIG. 214.—Jaws of a six month lion, after Weber. Milk teeth white, permanent dotted i, incisors; c, canines; m, molars; p, premolars. Only a few fishes (adult Acipenser, Coregonus, etc.) lack teeth, while in most they extend to the lining bones of the mouth and in some to the hyoid and branchial arches (pharyngeal bones). Usually they are conical, but they may be flattened and pavement-like or even form large plates, apparently by the coalescence of numbers of primitive teeth (dipnoi). In the amphibians the teeth are not so widely distrib- uted in the mouth, occurring on the margins of the jaws and on the palatines and vomers, rarely on the parasphenoid, while they are entirely lacking in Bufo and Pipa. Among the reptiles the turtles and some of the pterodactyls are toothless; most of the others have the teeth confined to the margin of the jaws, though they occur on the palatines and pterygoids in the snakes and lizards, and rarely (Sphenodon) on the vomer. While the conical shape prevails, the teeth present a great variety of forms, some of the theriomorphs closely simulating the mammals in their heterodont dentition. The teeth may be anchylosed to the summit of the jaws. 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
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1912
