Pig-nosed turtle

The pig-nosed turtle (Carettochelys insculpta), also known as the Fly River turtle, the pitted-shelled turtle, and the Warrajan, is a species of turtle which is native to northern Australia and southern New Guinea. It is the only living member of the genus Carettochelys and family Carettochelyidae, a family which also contains many fossil species with their closest relatives being the softshell turtles (family Trionychidae).

C. insculpta is the only living member of the genus Carettochelys, the subfamily Carettochelyinae, and the family Carettochelyidae, with Carettochelyidae being one of two families in the Trionychia, alongside Trionychidae (softshell turtles). Carettochelyidae has an extensive fossil record extending into the Paleogene and was formerly widespread, with fossils having been found in Asia, North America, Europe, Africa and Australia. Some literature claims two subspecies, but a 2010 paper rejects this. A fossil species of the genus, Carettochelys niahensis is known from the Neogene of Borneo.

The pig-nosed turtle is unlike any other species of freshwater turtle in its combination of traits. The feet are flippers, resembling those of marine turtles. The nose looks like that of a pig, having the nostrils at the end of a fleshy snout, hence the common name. The carapace is typically grey or olive, with a leathery texture, while the plastron is cream-coloured. Males can be distinguished from females by their longer and narrower tails. The pig-nosed turtles can grow to about 70 to 75 cm (28 to 30 in) straight carapace length, with a weight of over 20 kg (44 lb).

Unlike the soft-shelled turtles of the family Trionychidae, the pig-nosed turtle retains a domed bony carapace beneath its leathery skin, rather than a flat plate. It also retains a solid plastron, connected to the carapace by a strong bony bridge, rather than the soft margin of the trionychids.

The pig-nosed turtle is not completely aquatic. Little is known about its general behaviour, as there have been few studies in the wild. Its known extreme aggression in captivity suggests the species is markedly more territorial than most other turtles and tortoises. It seems to display a degree of social structure during the cooler dry season around the hydrothermal vents that line some river systems it inhabits.^{[citation needed]}

C. insculpta is omnivorous, eating a wide variety of plant and animal matter, including the flowers, fruit and leaves of figs, as well as preying upon crustaceans, molluscs and insects.

Females of C. insculpta reach maturity at 18 or more years, and males around 16 years. The females lay their eggs late in the dry season on sandy river banks.

When the offspring are fully developed, they will stay inside the eggs in hibernation until conditions are suitable for emergence. Hatching may be triggered when the eggs have been flooded with water or by a sudden drop in air pressure signaling an approaching storm.^{[citation needed]}