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Platysternidae: Currently there are five subspecies of P. megacephalum recognized: P. m. megacephalum, P. m. peguense, P. m. vogeli, P. m. tristernalis, and P. m. shiui. Big-headed turtles were first described in 1831 by J. E. Gray, with various subspecies advanced in 1870, 1969, and 1984 . Ernst and McCord described the most recent subspecies, P. m. shiui, in 1987. Some subspecies may be invalid, as the diagnostic characteristics used to separate them might be too variable to adequately differentiate between subspecies. Carl Ernst is investigating the relationships between the subspecies (Ernst and McCord, 1987). Currently the subspecies are designated based on differences in a number of characteristics, including the patterns on the plastron and carapace, the presence of growth annuli and posterior serrations on the carapace, and the shape and coloration of the head and jaws. Various subspecies are found in different parts of the turtle's range: P. m. megacephalum is found in southern China, while P. m. peguense occurs in southern Thailand and Burma. The most colorful subspecies, P. m. shiui, is located in northern Vietnam (Iverson, 1992). |
