Genus Heosemys

Stejneger, 1902
Forest turtles

Heosemys is a genus of five semi-terrestrial or semi-aquatic tropical Asian batagurines. The carapaces are usually flattened across the vertebrals, but still retain at least traces of a medial and two lateral keels, which are more pronounced in younger individuals. The posterior margin of the carapace is always serrated. Neurals are six sided and shortest posteriorly. The plastron is rigid, well-buttressed, and generally hingeless (females may have some kinetic movement of the posterior lobe to aid the passage of the rather large eggs). The entoplastron is usually crossed by the humero-pectoral seam. A temporal arch is absent from the short skull. The ethmoid fissure is broadly oval, and the small postlagenar hiatus is round. The anterior edge of the inferior parietal process is not flared outward, is separated from the jugal by the pterygoid, but touches the palatine. The orbito-nasal foramen is posteriorly placed at a level with the primitive caroticum foramen and bordered medially by the basisphenoid. Triturating surfaces of the jaws are narrow and ridgeless. Cloacal bursae are present.

Based on skull characters, McDowell (1964) thought Heosemys to be an isolated genus, without clear affinity to any other particular genus of his Geoemyda complex, although clearly a member of that complex. However, Bramble (1974) suggested that, on the basis of plastral kinesis and closing mechanisms, a Heosemys -like ancestor may have given rise to the genera Cuora, Cyclemys and Pyxidea, suggesting all four genera may be united in a Heosemys complex.
Moll et al. (1987) made a case for placing Heosemys silvatica in the genus Geoemyda, and recently, McCord et al. (1995) performed a preliminary cladistic analysis that seemed to suggest that H. depressa, H. leytensis, and H. silvatica should be reassigned to the genus Geoemyda; however, we consider it best to be conservative and retain these species in Heosemys until data from a more complete analysis is available.

Species identification
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