Genus Elseya

Gray, 1867
Australian snapping turtles

This is one of five short-necked chelid genera from Australia and New Guinea. The adult carapace is oval, depressed to somewhat domed, broadest behind the center, and with either a smooth or a serrated posterior rim. Juveniles have a vertebral keel which is lost in adults, and large adults may develop a medial groove. Neural bones are usually absent, but Rhodin and Mittermeier (1977) found four in an E. latisternum and three in an unidentified Elseya. A cervical scute is present in some species but absent in others. The plastron lacks a hinge and is usually long and somewhat narrow. Its hindlobe is notched posteriorly. Axillary buttresses are strong; inguinal buttresses are smaller and weaker, barely reaching the 5th costal bone. The intergular scute is narrow and rectangular; it completely separates the gulars, but not the humerals or pectorals. Cervical vertebrae are shorter than those beneath the carapace. The temporal arch is moderate, formed by the squamosal and expanded parietal bones; however, the parietals do not touch either the supraoccipital or quadrate bones. The nasal bones are not completely separated by the anterior process of the frontal bone. The frontals are not fused, and 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 touches the palatine. The triturating surface of the maxilla bears a medial ridge in only one species, E. dentata. The upper jaw is either unnotched medially or bears a slight medial indentation. The snout is long and usually protrudes, and there are usually a few prominent, large, conical tubercles behind the orbits. Dorsally, the head is covered with a single, well-developed, horny plate. The toes are webbed, and there are five foreclaws and four hindclaws.

There has been considerable debate about the validity of the genus Elseya. Due to morphological and genetical similarities, several authors proposed synonymization with Emydura (Goode, 1967; Gaffney, 1977; Frair, 1980; Bull and Legler, 1980; McDowell, 1983). Georges and Adams (1992), in a phylogenetical study based on electrophoresis, proposed to erect a new genus for the Elseya latisternum group.

Undescribed Taxa
Three species have currently been described, but Goode (1967), Cann (1978), Bull and Legler (1980), and Legler (1981) refer to several unnamed taxa.
At least five populations that are assigned to Elseya dentata may be regarded as separate taxa. In the Northern Territory region, one or possibly two taxa occur. Elseya sp (S Alligator R) is found in the Mary River, Alligator Rivers region and Arnhem Land of the Northern Territory. Most distinctive feature is its clear white, cream or yellow plastron. This is generally considered a distinct species, as electrophoresis revealed fixed differences between specimens taken from the South Alligator River and Elseya dentata proper from adjacent drainages (Georges and Adams, 1996). The status of Elseya sp (Roper R) from the Roper River, northeastern Northern Territory is unclear; its allozyme profile has not been studied yet. John Cann (pers. comm.) reports morphological differences.
Elseya sp (Nicholson R) is found in the Gregory-Nicholson drainage of the Gulf of Carpentaria region, northwestern Queensland. A recent morphological comparison by Thomson et al. (1997) revealed that the fossil described as Emydura lavarackorum by White and Archer (1994) shares all characters with living Elseya from the Nicholson drainage, including a sigmoidal shape of the sulcus between the humerals and pectorals on the plastron. In the absence of any diagnosable difference and the relatively young age of the fossil material, Thomson et al. (1997) proposed the fossil and extant population from the Nicholson drainage to be regarded a single species, Elseya lavarackorum.
Along the east coast of Queensland, three distinct taxa are found. The northernmost population, from the Johnstone River (Elseya sp (Johnstone R) [female (l) and male]; Elseya sp (Johnstone R) 2 [juvenile]), has four fixed allozyme differences (Georges and Adams, 1996). Large females (over 30 cm) of this taxon have a rather square carapace when observed in frontal view; it usually also has more annuli on the carapace than other species of the Elseya dentata group (John Cann, pers. comm.). The population from the Burdekin River (Elseya sp (Burdekin R)) is morphologically different from all other Elseya dentata in having a white head with a yellow crown. Possibly due to low samples sizes, Georges and Adams (1996) were unable to demonstrate difference between this species and the population from Johnstone River. Cann (1997c) recently described this species as Elseya irwini. The third distinct taxon is located in mid-coastal Queensland, in the drainages of the Fitzroy, Mary, and Burnett Rivers (Elseya sp (Raglan R); Elseya sp (Mary R)). This taxon has six fixed allozyme differences (Georges and Adams, 1996), and was named Elseya stirlingi by Wells and Wellington (1985), but this has not been accepted (see Family Chelidae for a discussion of this controversial paper). According to John Cann (pers. comm.), the marginals of juveniles are heavier serrated than in juveniles from the north. He also reports a difference in size between the Fitzroy and Mary River populations. Georges and Adams (1996), however, could not detect fixed allozyme differences throughout the Fitzroy-Burnett-Mary River area.
In New South Wales three undescribed Elseya taxa are found, referred to by Georges and Adams (1992, 1996) as the Elseya latisternum group. The Namoi River snapping turtle (Elseya sp (Gwydir R); Elseya sp (Namoi R); Elseya sp (Namoi R) 2; Elseya sp (Namoi R) 3) is an undescribed species with affinities to Elseya latisternum, found in the headwaters of the Darling River system of central New South Wales. Some populations are threatened by blindness, probably viral in origin (Arthur Georges, pers. comm.). The 1996 IUCN Red List of Threatened Animals lists this species (as Elseya sp. 1) as Endangered (B1+2c). A sibling pair of species is found in the coastal drainages of the Bellinger and Manning Rivers. Both are morphologically quite similar, but the Bellinger River snapping turtle (Elseya sp (Bellinger R); Elseya sp (Bellinger R) 2) has a bluish tinge to its plastron, whereas the Manning River snapping turtle (Elseya sp (Manning R)) has a yellowish tinge, and distinctive black bars on its undertail. Besides, the Bellinger turtle has expanded neural bones beneath the scutes of the carapace, but this cannot be determined by external examination. Both species have a bright yellow band along the head and neck and adults lack a central groove on the carapace as found in Elseya latisternum and Elseya sp. from the Namoi River (Cann, 1978, 1997a). Despite their morphological similarities (they were treated as one form by Cann, 1978), these species genetically are very distinct, differing in 20% of their loci (Georges and Adams, 1996). Very recently, Cann (1997a) described the Bellinger species as Elseya georgesi, Georges' snapping turtle. As Cann (1997a) uses Elseya purvisi for the Manning River turtle, this seems one of the few names from Wells and Wellington (1985) that will find scientific acceptance. Both species are listed (as Elseya sp. 2 and Elseya sp. 3) in the 1996 Red List as Data deficient.

Species identification
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