Bonaparte, 1836
Australian short-necked turtles
Recognition
The short-necked side-necks of the genus Emydura are semi-aquatic and restricted to Australia and New Guinea. The adult carapace is oval to elliptical, somewhat domed, usually has a smooth posterior rim, and lacks a vertebral keel. A slight medial groove may be present on the carapace of larger adults, and that of hatchlings and juveniles is keeled and posteriorly serrated. Usually no neural bones are present, but a well-developed cervical scute is present. The plastron is hingeless, usually long and somewhat narrow, and notched posteriorly. Much of the carapacial opening is left uncovered. Both axillary and inguinal buttresses are strong; the inguinal buttress extends to the 5th or between the 5th and 6th costal bones. The intergular scute is longer than broad and is dilated posteriorly; it completely separates the gular scutes but not the humerals or pectorals. Cervical vertebrae are not longer than those beneath the carapace. The temporal arch is moderate, formed by the squamosal and parietal bones; however, the parietal does not touch either the supraoccipital or the quadrate. Nasal bones are not completely separated by the anterior frontal process and the frontals are not fused. The prefrontals are not exposed along the dorsal margin of the external nares. Beneath the cranium there is no quadrate-basisphenoid contact, but the vomer and palatine meet. The jaws lack ridges on the triturating surfaces and the upper jaw is neither hooked nor notched. The snout is short and flattened (only slightly projecting), and there are many small flattened tubercles behind the orbits. Smooth skin covers the dorsal surface of the head. The toes are webbed, and there are five foreclaws and four hindclaws.
Remark
Wells and Wellington (1984, 1985) have resurrected the name Chelymys Gray, 1844 for macquarii and signata, and put subglobosa, krefftii, and victoriae in a new genus (Tropicochelymys), but these changes have not been accepted. Emydura Bonaparte, 1836 has priority over Chelymys, and should also be recognized owing to its common usage for over a century (Stimson, 1986).
Undescribed Taxa
Six species are currently recognized, although Goode (1967), Cann (1978), Bull and Legler (1980), Legler (1981), and Georges and Legler (in press) refer to several other yet undescribed taxa.
John Cann (pers. comm.) mentions Emydura sp (King Edward R), a small form from the King Edward River, northern Western Australia. A melanistic pigmy form of E. krefftii (Emydura sp (Fraser Is); Emydura sp (Fraser Is) 2) occurs in the dune lakes of Fraser Island and the Cooloola Peninsula. The Fraser Island short-necked turtle differs from of the mainland populations in coloration (it is melanistic), in body size (it is dwarfed) and in several key ecological attributes (size at maturity, dimorphism, reproductive parameters; Georges and Legler, in press). This form was designated asTropicochelymys insularis by Wells and Wellington (1985), but see Family Chelidae for a discussion. Emydura sp (Cooper Creek) is a large distinctive form with affinities to E. krefftii, restricted to the inland Cooper Creek and Strzelecki drainages of Queensland. Young individuals of this form have a yellow head stripe, but adults lacks facial markings (Cann, 1978). The Cooper Creek turtle was named Chelymys windorah by Wells and Wellington (1985); they also named populations from the Leichhardt River, Queensland (as Tropicochelymys leichhardti), and from the Macleay River (as Chelymys cooki) and the upper Hunter River (as C. johncanni), New South Wales, but all without adequate descriptions.
An electrophoretical study by Georges and Adams (1996) revealed no differences between the Fraser Island and Cooper Creek shortnecks and Emydura krefftii. In fact, they were also unable to find electrophoretical differences between Emydura krefftii, E. signata, and E. macquarrii, and additionally pointed out the variability in morphological characters separating these species. According to Georges and Adams (1996), E. krefftii (including the Fraser Island and Cooper Creek forms), E. signata, and E. macquarrii should be synonymized.
Species identification
Jump to the key: Page 70: Genus Emydura