Macrochelys rarely leaves the water except to nest, whereas Chelydra commonly makes terrestrial forays in addition to nesting on land. The karyotype is 2N = 52.īiology: Chelydra and Macrochelys are aquatic turtles ( Fig. The plastron is greatly reduced and cruciform, and the plastral bridge is rigid the skull roof is strongly emarginated. The pelvic girdle flexibly articulates with the plastron, and the ilium lacks a thelial process. The neck withdraws vertically, and this mechanism is reflected in an 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 amphicoelous and opisthocoelous caudal vertebrae. The plastron lacks a mesoplastron, and the plastral buttresses articulate loosely or firmly with the costals of the carapace the carapace has 11 pairs of sutured peripherals around its margin and a nuchal with large costiform processes. The facial nerve lacks a hyomandibular branch. An epipterygoid is present in the skull the internal carotid canal lies in the pterygoid, and the parietal–squamosal and postorbital–squamosal are in strong contact. The jaw closure mechanism of chelydrids articulates on a trochlear surface of the otic capsule and is enclosed in a synovial capsule. They have large heads and broad, flattened carapaces with reduced plastra they possess among the longest tails of all turtles.
Geographic distribution of the extant Chelydridae.Ĭharacteristics: Chelydrids range in adult CL from the giant Macrochelys temminckii at 80 cm (maximum) to the smaller Chelydra serpentina at a maximum of 47 cm.