Family Podocnemididae

Order Testudines
Suborder Pleurodira

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Family Podocnemididae

Madagascan Big-headed Turtles and American Sideneck River Turtles

Podocnemis unifilis

Appearance: Podocnemidids have broad domed, streamlined shells adapted to swimming.

The jaw closure mechanism articulates on a pterygoid trochlear surface that lacks a synovial capsule but contains a fluid-filled saclike duct from the buccal cavity. Both epipterygoid and parietal-squamosal contacts are missing in the skull; the internal carotid canal lies in the prootic, and the postorbital has strong contact to the squamosal. The facial nerve has a hyomandibular branch. The plastron has a mesoplastron and well-developed plastral buttresses that articulate with the costals on each side of the carapace; the carapace has 11 pairs of sutured peripherals around its margin and a nuchal without costiform processes. The neck withdraws horizontally, and this mechanism is reflected in an anteriorly oriented articular surface of the first thoracic vertebra; other vertebral traits are the inclusion of the 10th thoracic vertebra in the sacral complex and procoelous caudal vertebrae. The pelvic girdle is firmly fused to the plastron, and the ilium lacks a thelial process. The karyotype is 2N = 28 (after Zug et al. 2001).

Size: 20 cm (Podocnemis erythrocephala) to 80 cm (Podocnemis expansa) carapace length (adults).

Distribution: Madagascar, Northern South America.

Habitat: Rivers and other moderate currents.

Food: Mostly plants but occasionally small, slow-moving animal prey and carrion is also eaten.

Reproduction: Nesting takes place on sandy river banks. P. expansa nests in larger groups and each female lays s60 to 120 eggs (smaller species produce smaller clutches). Incubation periods in P. expansa eggs is 42 to 47 days, whereas those of P. vogli require 127 to 149 days.