. The biology of the amphibia. Amphibians. 124 THE BIOLOGY OF THE AMPHIBIA. with his snout. No males, however, opened their mouths during any phase of the courtship and no biting was observed even in cases where courting pairs were crowded together in a small aquarium. Hence the elongate maxillary and dentary teeth of Eurycea seemed to have no specific function. In the related Gyrinophilus no sexual differences in dentition appear. In G. porphyriticus, the purple salamander, the teeth are all bicuspid. In the closely related G. danielsi, however, the teeth of both jaws are elongate and monocus
. The biology of the amphibia. Amphibians. 124 THE BIOLOGY OF THE AMPHIBIA. with his snout. No males, however, opened their mouths during any phase of the courtship and no biting was observed even in cases where courting pairs were crowded together in a small aquarium. Hence the elongate maxillary and dentary teeth of Eurycea seemed to have no specific function. In the related Gyrinophilus no sexual differences in dentition appear. In G. porphyriticus, the purple salamander, the teeth are all bicuspid. In the closely related G. danielsi, however, the teeth of both jaws are elongate and monocuspid. There is no evidence that these two species of Gyrinophilus differ essentially in feeding habits, and yet there is nearly as much difference in their dentition as between the two sexes of Eurycea. If the elongation of the teeth in the latter is merely due to "neutral" genes which happen to be sex-linked or sex-limited, the occurrence of a similar modification in both sexes of G. danielsi would Fig. 46.—The male Manculus quad- , , ridigitatus has the naso-labial grooves Seem to be due 10 Similar of each side extended into a cirrus. As genes which, however, have in many other plethodontids, the pre- -a A +u- T l A maxillary teeth are elongated, directed avoided tniS linkage. An forward, and exposed during the breed- apparent difference is never- theless to be found in the genesis of the teeth, since those of the male Eurycea fluctuate with the season and are apparently under the control of the sex hormone, while those of Gyrinophilus are not known to be influenced by hormones. The modification of the teeth of vertebrates is generally believed to be closely correlated with changes in food habits. Nevertheless, the most extreme types of dental modification in Amphibia fail to show this correlation. Many cases of dental change in the evolution of the frogs resemble those of urodeles. For example, in the ranid Dimorphognathus africanus (Fig. 40B) the premaxillary and
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Keywords: ., bookcentury1900, bookpublishernewyorkmcgr, booksubjectamphibians
