Reptiles and Birds

Abstract

We know even less about the reptilian neural crest than we do about that of fishes. Indeed, very few species have even been examined. In the one experimental study in which presumptive neural crest cells have been extirpated from reptilian embryos, Toerien (1965a) used embryos of the snapping turtle, Chelydra serpentina, to provide evidence that the mandibular and pharyngeal skeletons arise from neural crest cells and that the skeletogenic neural crest is regionalized as in other vertebrates (see Fig. 5.4). Extirpation of pre-optic cranial neural folds (and with them any resident neural crest cells) at the 4 to 6 somite stage resulted in embryos that lacked Meckel’s and quadrate cartilages. Extirpation of postoptic neural folds caudal to the level of the second pair of somites produced embryos lacking hyoid arch cartilages and the columella, and with abnormal tympanic membranes.