Asian box turtles
The nine Southeast Asian box turtles of the genus Cuora live in habitats ranging from the temperate or subtropical (aurocapitata, flavomarginata, pani) to tropical (amboinensis, galbinifrons). Adult carapaces are either low or high domed, with a medial and two parallel longitudinal keels and a smooth posterior rim. Neural bones are hexagonal and short sided posteriorly. The plastron has a hinge between the pectoral and abdominal scutes (between the hyo- and hypoplastra) that allows the two plastral lobes to move and close the shell. The hindlobe may or may not be notched posteriorly. The entoplastron is intersected by the humero-pectoral seam. There is no bridge and the plastral buttresses have been mostly resorbed; the plastron is connected to the carapace by a ligament. The skull is short, and usually has a complete temporal arch (incomplete in C. flavomarginata). The squamosal touches the postorbital but not the jugal; the jugal is separated from the quadratojugal by the postorbital (the quadratojugal is absent in C. flavomarginata and C. galbinifrons). The anterior edge of the inferior parietal process is not outwardly flared, and is separated from the jugal by the pterygoid, but does touch the palatine. McDowell (1964) noted that the pterygoid fails to grow up and over the medial surface of the quadrate to exclude it from the wall of the cavernosus canal. Triturating surfaces of the jaws are narrow, and the premaxillae meet to form a hooklike process. The toes are at least partially webbed.
Bour (1980b) and Hirayama (1984) have reassigned the species flavomarginata and galbinifrons to the genus Cistoclemmys Gray, 1863a, retaining the generic name Cuora for the other species. They base these designations on cranial features (see Hirayama, 1984, for a descriptive list) and the supposed absence of an interanal seam. In doing this they disregard such important characters as carapacial structure and plastral hinge structure and kinetics (Bramble, 1974). Examination of series of flavomarginata and galbinifrons by Ernst has shown that loss of the interanal seam (or the low ridge representing it) results from abrasion. Small juveniles had the seam (or ridge) while larger juveniles showed a progressive loss with increased shell length. Also, some adult amboinensis, especially those from the Philippines, lose this seam. In addition, Sites et al. (1984) have studied the biochemical relationships among batagurine turtles and have supported the assignment of flavomarginata to Cuora. The interspecific relationships within Cuora are currently being studied by Ernst, and we feel it is premature to split the genus.
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