The Mary River turtle is one of Australia's largest turtles.
Specimens in excess of 50 cm in carapace length have been recorded.
Hatchlings have a straight carapace length of 2.0–3.5 cm.
Adult Mary River turtles have an elongated, streamlined carapace that can be plain in colour or intricately patterned.
Overall colour can vary from rusty red to brown and almost black.
The plastron varies from cream to pale pink.
The skin colouration is similar to that of the shell and often has salmon pink present on the tail and limbs.
The iris can be pale blue.
Mary River turtles use bimodal respiration, and so are capable of absorbing oxygen via the cloaca whilst underwater.
 However, they do regularly come to the surface to breathe air in the usual way.

A unique feature of the male Mary River turtle is the tail, which can measure almost two-thirds of the carapace length.
 The tail has haemal arches, a feature lost in all other modern turtles.
It is probably a derived feature, but its function is not understood.
Another unique feature is the exceptionally long barbels under the mandible.
Proportionately, the Mary River turtle has the smallest head and largest hind feet of all the species within the catchment, which contributes to its distinction of being the fastest swimmer.

The turtle is occasionally informally referred to as the green haired turtle due to the fact that many specimens are covered with growing strands of algae which resemble hair.
The Mary River turtle is one of Australia's largest turtles. Specimens in excess of 50 cm in carapace length have been recorded. Hatchlings have a straight carapace length of 2.0–3.5 cm. Adult Mary River turtles have an elongated, streamlined carapace that can be plain in colour or intricately patterned. Overall colour can vary from rusty red to brown and almost black. The plastron varies from cream to pale pink. The skin colouration is similar to that of the shell and often has salmon pink present on the tail and limbs. The iris can be pale blue. Mary River turtles use bimodal respiration, and so are capable of absorbing oxygen via the cloaca whilst underwater.  However, they do regularly come to the surface to breathe air in the usual way.
A unique feature of the male Mary River turtle is the tail, which can measure almost two-thirds of the carapace length.  The tail has haemal arches, a feature lost in all other modern turtles. It is probably a derived feature, but its function is not understood. Another unique feature is the exceptionally long barbels under the mandible. Proportionately, the Mary River turtle has the smallest head and largest hind feet of all the species within the catchment, which contributes to its distinction of being the fastest swimmer.
The turtle is occasionally informally referred to as the green haired turtle due to the fact that many specimens are covered with growing strands of algae which resemble hair.
Mary River turtle