Andrew A. Burbidge and Gerald Kuchling
Wildlife Management Program No. 37
Department of Conservation and Land Management, 2004
About the document
The Western Swamp Tortoise (Pseudemydura umbrina Siebenrock, 1901) is a short-necked freshwater tortoise that monotypically represents the sub-family Pseudemydurinae (family Chelidae, sub-order Pleurodira) (Gaffney and Meylan 1988). P. umbrina is the smallest of the Australian chelids (Burbidge 1967, Burbidge et al. 1974). Adult males do not exceed a carapace length of 155 mm or a weight of 550 g. Females are smaller, not growing beyond 135 mm 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.
The colour of living P. umbrina varies with age and swamp type. The shell of hatchlings is grey above and bright cream and black below. The carapace in adults is usually similar in colour to the swamp water 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. There are two small barbels.
The Western Swamp Tortoise can be easily distinguished from the only other freshwater tortoise (or turtle) occurring in the south-west of Western Australia by its short neck; the Oblong Tortoise (Chelodina oblonga) has a neck that is equal to or longer than the length of its shell.
The Austrian J.A. Ludwig Preiss, who collected in Western Australia from 1839 to 1841, sent the first Western Swamp Tortoise known to science to the Vienna Museum in 1839. The specimen, which was labeled "New Holland", was named by Siebenrock (1901), who provided further details and comments on the species in 1907. No further specimens were collected until 1953 when two were found near Warbrook, only 30 km north-east of the centre of the city of Perth. Glauert (1954) described these as a new species, Emydura inspectata, but this was shown to be a synonym of P. umbrina by Ernest Williams (1958) of Harvard University.
A relict species, apparently little changed since the Miocene, P. umbrina is the only member of its genus and has no close relatives among other members of the Chelidae (Burbidge 1967; Burbidge et al. 1974; Gaffney 1977). P. umbrina is so different from other members of the family that a separate sub-family, the Pseudemydurinae, has been proposed for it (Gaffney 1977, Gaffney and Meylan 1988). The only fossil records of Pseudemydura are a portion of a skull and a pygal bone from the early Miocene Riversliegh deposits of north-west Queensland, which show only slight differences from modern specimens (Gaffney et al. 1989, Archer et al. 1991).