Genus Natator

McCulloch, 1908
Flatback turtles

This is a monotypic genus; its single species is N. depressus. The flattened, oval carapace lacks a vertebral keel, and is barely serrated posteriorly. Four pleural scutes are present on each side, and five vertebrals are present. The skeletal system most closely resembles that of Lepidochelys or Caretta. Following the nuchal are 9-12 neurals, most are hexagonal but shape-variation is common. The most posterior neurals form a series of smaller bones than those neurals more anterior (except for the second neural, which is also short). Eleven pairs of peripherals are present with the tenth pair not touching a rib. The carapace also has three suprapygals and one pygal. The hingeless plastron has an intergular scute and a pair of postanal scutes. Four inframarginal scutes lie on each bridge. In the skull, the vomer contacts the premaxillae and separates the maxillae. The triturating surfaces of the maxillae are ridged, but those of the premaxillae are not. The frontal bones are excluded from the orbital rims. A single pair of prefrontal scales and three postocular scales are present. The upper jaw does not strongly project into a hooked beak. Each forelimb has a single claw.

Formerly this species was included with Chelonia mydas in the genus Chelonia, but detailed morphological studies by Limpus et al. (1988) and Zangerl et al. (1988) and biochemical analyses by Limpus et al. (1988) have show N. depressus has a greater affinity with Lepidochelys than with C. mydas. Therefore both Limpus et al. (1988) and Zangerl et al. (1988) independently resurrected the genus Natator McCulloch, 1908 for this species.