Genus Cyclemys

Bell, 1834
Asian leaf turtles

The oriental genus Cyclemys shares a common plastral closing mechanism with Pyxidea and Cuora and may have evolved from a Heosemys- like ancestor (Bramble, 1974). McDowell (1964) has also pointed out its relationship to the genus Geoemyda. One widespread species, C. dentata, and two poorly known species, C. tcheponensis and Cyclemys n.sp. are currently assigned to Cyclemys.
The adult carapace is oval, slightly arched, and longer than wide; that of juveniles is flattened and rounder. A medial and two lateral keels are present, but these become lower with age. The hexagonal neurals are short sided posteriorly, and the posterior
border of the carapace is serrated, more so in juveniles. The plastron is large, and a movable hinge usually develops between the hyoplastron and the hypoplastron bones at about 16-19 cm carapace length (Theobald, 1970), but may be absent or at least externally invisible (Smith, 1931). This hinge allows the anterior lobe to move, but it cannot entirely close. In the adult, the plastral buttresses are resorbed and the plastron is connected to the carapace only by a ligament. The skull usually has a complete temporal arch, but the squamosal does not normally touch the jugal. Ventrally, the jugal is broad. The parietal touches the quadrate above the foramen for the trigeminal nerve; however, the anterior edge of the inferior parietal process does not touch the jugal or palatine. The ethmoidal fissure is narrowly triangular or shaped like a keyhole. Triturating surfaces of the maxillae are narrow and ridgeless. Cloacal bursae are present. The toes are webbed.

Fritz et al. (1996c) reported additional variation in this genus. They distinguished four taxa, but did not apply names to these forms. In 1997(b), Iverson and McCord described Cyclemys atripons from extreme southeastern Thailand and adjacent southwestern Cambodia. Simultaneously, Fritz et al. (1997) assigned the following names to their previously unnamed taxa: A—Cyclemys oldhamii (Gray, 1863a), B—C. tcheponensis (Bourret, 1939), C—C. dentata sensu stricto (Gray, 1831b), and D—C. pulchristriata n.sp. Apparently C. atripons is synonymous with C. pulchristriata (John B. Iverson, pers. comm.), but as it is yet uncertain which paper was published first, this species has been included as Cyclemys n.sp. A discriminate functions analysis performed by Iverson (in Iverson and McCord, 1997) does not support the distinctiveness of either C. tcheponensis or C. oldhamii, but does indicate that the populations of Cyclemys in Borneo and China are unique.
Despite the recent description of Cyclemys n.sp. (McCord and Iverson, 1997b; Fritz et al., 1997) and the revision of the genus by Fritz et al. (1997), the exact distribution patterns and habitat requirements of Cyclemys remain largely obscure. An intensive field study, coupled with DNA research, should provide better insight in the status of its species.

Species identification
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