Development of the skull of the Hawksbill Seaturtle, Eretmochelys imbricata

The embryonic development of the cranium of the Hawksbill Seaturtle (Eretmochelys imbricata) is described on the basis of cleared and double-stained specimens. Illustrations and descriptions of the chondrocranium at Stage 25 form the basis of comparison with similar data for the Loggerhead Seaturtle, Caretta caretta. Morphological changes through prehatching ontogeny are described for all dermal and endochondral elements of the skull and jaws, and the sequence of appearance and ossification of these elements are compared with similar data for Chelonia mydas, Natator depressa, and Dermochelys coriacea. Comparisons among suggest that a possible remnant of the dorsal edge of the orbital cartilage remains and represents a portion of the posterior orbital cartilage in C. caretta, representing a novel pattern of development for the posterior orbital cartilage for this species. Anatomy of cartilages of the orbitotemporal region are described for E. imbricata and C. caretta. J. Morphol. 274:1124-1142, 2013. (c) 2013 Wiley Periodicals, Inc.