Understanding of evolutionary history and speciation events to inform phylogeography of extant species can be gleaned from the fossil record. However, the fossil record for Australian freshwater turtles contains many gaps and interpretation of the fossils that are known is difficult because of poor knowledge of the morphology of extant forms. There are no fossils currently assigned to short-necked turtles in the genus Myuchelys. In an alternative approach, morphological characters of the extant species Myuchelys bellii, Myuchelys georgesi, Myuchelys latisternum, and Myuchelys purvisi were mapped against their current molecular phylogeny. The cryptic species pair, M. georgesi and M. purvisi, are morphologically very similar, but distant phylogenetically, and their common ancestor includes M. latisternum and M. bellii in its decendents. This suggests that current shared morphology of M. georgesi and M. purvisi represents a suite of symplesiomorphies (shared primitive characters). These characters include presence of a cervical scute, lack of prominent neck tubercles, a relatively small head size, minor or no serrations of marginal scutes, an oval carapace, and a smooth head shield extending down the parietal arch toward the tympanum. This commonality of characters of this cryptic species pair represents a rare insight to the ancestral phenotype of the Myuchelys. The loss of the cervical scute and presence of enlarged neck tubercles, a large robust head and furrowed head shield, deep serrated shell margins, and compressed shell profile in M. bellii and M. latisternum are synapomorphies (shared derived characters). There is no morphological support for the distinction at the level of species or subspecies between discrete populations of M. bellii. A dichotomous key to species is provided.
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Vol. 12 • No. 1