The western swamp turtle or western swamp tortoise (Pseudemydura umbrina) is a critically endangered species of freshwater turtle endemic to a small portion of Western Australia.[4][5] It is the only member of the genus Pseudemydura in the monotypic subfamily Pseudemydurinae.[6]
It is the sister taxon to the subfamily Chelodininae. As a consequence of the greatly altered habitat in the area in which it occurs near Perth, Western Australia, it exists in small fragmented populations, making the species critically endangered.
The accepted description of the species by Friedrich Siebenrock was published in 1901.[5]The first specimen of the western swamp tortoise was collected by Ludwig Preiss in 1839 and sent to Vienna Museum. There it was labelled "New Holland" and was named Pseudemydura umbrina 1901 by Seibenrock. No further specimens were found until 1953. In 1954, Ludwig Glauert named these specimens Emydura inspectata, but in 1958, Ernest Williams of Harvard University showed that to be a synonym of Pseudemydura umbrina.[7]
Adult males do not exceed a length of 155 mm or a weight of 550 g. Females are smaller, not growing beyond 135 mm in carapace length or a weight of 410 g. Hatchlings have a carapace length of 24–29 mm and weigh between 3.2 and 6.6 g.[7]
The colour of the western swamp turtle varies dependent on age and the environment where it is found. Typical colouration for hatchlings is grey above with bright cream and black below. The colour of adults varies with differing swamp conditions, and varies from medium yellow-brown in clay swamps to almost black with a maroon tinge in the black coffee-coloured water of sandy swamps. Plastron colour is variable, from yellow to brown or occasionally black; often there are black spots on a yellow background with black edges to the scutes. The legs are short and covered in scale-like scutes and the feet have well-developed claws. The short neck is covered with horny tubercles and on the top of the head is a large single scute. It is the smallest chelid found in Australia.
The only other species of freshwater turtle occurring in the southwest of Western Australia is the southwestern snake-necked turtle (Chelodina oblonga). It has a neck equal to or longer than its shell, making the two species from south west Western Australia easily distinguishable.