The ontogeny of the shell in side‐necked turtles, with emphasis on the homologies of costal and neural bones

摘要: Although we are starting to understand the molecular basis of shell development based on study cryptodires, basic comparative ontogenetic data for other major clade living turtle, pleurodires, largely missing. Herein, developmental and phylogenetic relation between bony endoskeleton Pleurodira examined by studying histological serial sections nine specimens three different species, including an series Emydura subglobosa. Emphasis is given portion carapace in which ribs vertebral spinous processes become part carapace. Central questions how neurals costals formed pleurodiran turtles, whether endoskeletal or exoskeletal origin, what factors relate neural reduction some Pleurodira. The do not develop as independent ossification centers, but they initial outgrowths periosteal collar arches. Slightly later development, both elements continues without a distinct periosteum metaplastically ossifying precondensed soft-tissue integumentary structures. Through ontogeny, turtles studied closely associated with hypaxial intercostalis musculature while epaxial interspinalis connects We here propose alternative structural hypothesis and, ultimately, complete loss series. spp. may be linked heterochrony, accompanied restricted influence epidermal–dermal interaction bone formation. J. Morphol., 2008. © 2008 Wiley-Liss, Inc.