|
Emydidae Emydines have oval to oblong and moderately domed carapaces; the plastron is large and occasionally hinged (namely in Emys, Emydoidea, and Terrapene), i.e. they can close their shells to some extent. The jaw closure mechanism articulates on a trochlear surface of the otic capsule and is enclosed in a synovial capsule. An epipterygoid is present in the skull; the internal carotid canal lies in the pterygoid, and the parietal but not the postorbital touches the squamosal. The facial nerve lacks a hyomandibular branch. The plastron lacks a mesoplastron, and the plastral buttresses usually articulate with the costals of the carapace; the carapace has 11 pairs of sutured peripherals around its margin and a nuchal without costiform processes. The neck withdraws vertically, and this mechanism is reflected in a anteroventrally oriented articular surface of the first thoracic vertebra; other vertebral traits are the exclusion of the 10th thoracic vertebra from the sacral complex and procoelous caudal vertebra. The pelvic girdle flexibly articulates with the plastron, and the ilium lacks a thelial process. Sexual dimorphism is common and particularly striking in Pseudemys and Graptemys (after Zug et al. 2001). |
