Myuchelys latisternum (GRAY, 1867)
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Myuchelys latisternum
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| Higher Taxa | Chelidae, Chelodininae, Pleurodira, Testudines (turtles) |
| Subspecies | |
| Common Names | E: Northern Australian Snapping Turtle, Saw-shelled Turtle |
| Synonym | Elseya latisternum GRAY 1867 Euchelymys spinosa GRAY 1871 Elseya latisternon — GRAY 1871 Emydura latisternum — BOULENGER 1889 Emydura signata AHL 1932 Emydura latisternum — WERMUTH & MERTENS 1977 Elseya latisternon — THIEME 1984 Elseya latisternum — COGGER 2000: 194 Elseya latisternum — BONIN et al 2006 Elseya latisternum — FRITZ & HAVAS 2007 Wollumbinia latisternum — WELLS 2007 (unavailable name) Wollumbinia latisternum — HAMANN et al. 2008 Wollumbinia latisternum — WELLS 2009 Wollumbinia dorsii WELLS 2009 (fide THOMSON & GEORGES 2010) Wollumbinia spinosa — WELLS 2009 (unavailable name) Myuchelys latisternum — THOMSON & GEORGES 2009 Wollumbinia latisternum — WILSON & SWAN 2010 Myuchelys latisternum — GEORGES & THOMSON 2010 Myochelys latisternum — VALVERDE 2010 (in error) Myuchelys latisternum — TTWG 2014: 434 Wollumbinia latisternum — COGGER 2014: 255 |
| Distribution | NE Australia (from the Cape York Peninsula southward to northern New South Wales; Northern Territory, Queensland) Type locality: "North Australia”. dorsii: Australia (New South Wales); Type locality: Richmond River, near Wiangaree, New South Wales. |
| Reproduction | oviparous. |
| Types | Syntypes: BMNH 67.5.13.19-20, Cape York Qld, collected by E. Dämel, purchased Museum Godeffroy. See Cann & Sadlier (2017) and SMales et al. 2019 for discussion of the identity of the type specimens. Holotype: BMNH 1946.1.22.77 [Euchelymys spinosa] Holotype: AMS R172224, adult female in the Australian Museum, Sydney, NSW. Collected by Richard W. Wells on 6 December, 2008. The holotype was taken active at 1500 hrs in 1-2 metres water depth in a riffle zone over a mixed sediment bottom of basalt, sand and flood silt. [dorsii] |
| Diagnosis | Diagnosis (Myuchelys): A member of the short-necked chelid turtles of the Australasian region which, excluding Pseudemydura umbrina (Siebenrock, 1901), together form a well-established clade (Georges & Adams, 1992; Georges, et al., 1998). Differs from other short-necked turtles of the clade in possessing the following combination of characters (Table 1): Absence of a well-developed alveolar ridge on the triturating surfaces and underlying bones of the jaw (Fig. 1B) (present only in the redefined Elseya, Fig. 1A); parietal arch of skull wide, nearly as wide as tympanum (Fig. 2) (narrower than the tympanum in Elseya and Emydura); large distinctive head shield, entire, that extends in part down the parietal arch toward the tympanum (absent in Emydura, not extending down the parietal arch in Elseya, Rheodytes and Elusor); ilium-carapace suture involves pleurals 7–8 and the pygal (as in Elusor but distinct from the condition in Elseya and Emydura); anterior bridge strut is confluent with the rib-gomphosis of pleural one; no angle of intersection between these two bony units when viewed ventrally (as in Elusor, but unlike Elseya, Emydura and Rheodytes – see Fig. 1 and 2 of Thomson, et al., 1997). Diagnosis (of Wollumbinia): Wollumbinia is distinguished from the genus Elseya principally by the lack of a distinct median alveolar ridge on the upper jaw - which is present in all species of Elseya. Some other distinguishing features of the genus Wollumbinia are: large plastron with very rounded anterior lobe, which in some populations may extend past the level of the carapace when viewed from above; intergular about as wide as, or wider than the adjacent gulars; nuchal shield may be present or absent - but when present, usually a very narrow structure; head strong in appearance, fairly broad and deep, with a relatively wide mandibular symphysis in maturity and without a distinct median alveolar ridge on the upper jaw; horny plate (casque) on top of the head extends well off the dorsal of the head down almost as far as the tympanum; usually two to four small white barbels under the chin (although in some barbels are barely in evidence); in juveniles the head appears proportionally quite large, with a very prominent snout, but with age the head shape alters somewhat, with the snout becoming much reduced, presenting a flatter appearance to the face on side view by the time they reach maturity; the dorsal part of the neck is covered with small distinctly pointed tubercles, but in some there are also much enlarged (longer) sloping tubercles - forming a scattering of spine-like protuberances on the upper neck region; the shape of the mature carapace may be elongated or rounded depending on the population; hatchling carapace morphology varies slightly depending upon the location, but overall, most are ovate in appearance, with a distinct vertebral keel (but all trace of the vertebral keeling of the carapace is lost with maturity- replaced with a moderate central vertebral groove); the rear marginals are distinctly serrated, and depending upon the species in the group, this posterior serration to the carapace may either disappear with age, or may be retained into adulthood. Diagnosis (dorsii): A moderately large freshwater turtle of the Family Chelidae, of the genus Wollumbinia Wells 2007 and assignable to this genus by the absence of a distinct median alveolar ridge on the upper jaw - which is present in all species of Elseya. Readily separated from all other species of Wollumbinia by the following combination of character states: In Wollumbinia dorsii the mature carapace is rounded in shape (vs elongated in Wollumbinia latisternum); hatchling carapace morphology ovate in appearance, with a distinct vertebral keel (but all trace of the vertebral keeling of the carapace is lost with maturity- replaced with a moderate central vertebral groove); nuchal shield may be present or absent - but when present, usually very narrow; rear marginals of carapace are moderately to sharply serrated when young but this posterior serration to the carapace becomes much reduced to a smoothly ragged edge (vs serrations prominent throughout life, and largely retained as a jagged edging into adulthood in Wollumbinia latisternum). The plastron is relatively large with a very rounded anterior lobe, which in some specimens may extend to about the level of or just slightly beyond the carapace when viewed from above. The plastron in Wollumbinia dorsii also tapers strongly towards the posterior to a much greater extent than in Wollumbinia latisternum. In Wollumbinia latisternum the plastron is relatively larger at both the posterior and the anterior parts and the plastron tends to project significantly beyond the carapace anteriorly; intergular usually narrower than the adjacent gulars (vs about as wide as, or wider than the adjacent gulars in Wollumbinia latisternum; Head strong in appearance, fairly broad and deep (but generally smaller than in mature Wollumbinia latisternum), with a relatively wide mandibular symphysis in maturity and without a distinct median alveolar ridge on the upper jaw; horny plate (casque) on top of the head extends well off the dorsal of the head down to as far as the tympanum; usually two, but sometimes 3 or 4 small grey barbels under the chin (barbels 2-4, smaller and white in Wollumbinia latisternum); snout very prominent (vs more rounded and less prominent in Wollumbinia latisternum), dorsal part of the neck is covered with much enlarged sloping tubercles – interspersed with a scattering of wart-like protuberances on the upper neck region (vs a lower number of smaller distinctly pointed tubercles in Wollumbinia latisternum); limbs without a distinct line of white coloured enlarged scales on hind limbs (vs white limb scales present in Wollumbinia latisternum). This new species attains a maximum carapace length of about 230mm with females being larger than males (vs about 300 mm in Wollumbinia latisternum) and it does not exude the characteristic musk odour of Wollumbinia latisternum. In colouration, Wollumbinia dorsii varies significantly from topotypic Wollumbinia latisternum and indeed from all other members of the genus Wollumbinia, with the possible exception of Wollumbinia bellii. In Wollumbinia dorsii the mandibles are pale creamish sometimes flushed with yellow, with a faint inclusion of darker grey in places; this paler facial colouration doesn’t usually extend much beyond the jaws, with the side of the head and the anterior portion of the neck being greyish, tinged with greenish blue (vs yellowish-cream mandibles in Wollumbinia latisternum that extends as a pale yellow or cream stripe along the side of the head, through the tympanum and along the neck to the forelimbs). The throat is fairly evenly coloured dark greyish in mature Wollumbinia dorsii whereas in Wollumbinia latisternum the dark greyish throat is usually suffused with creamish to yellowish speckling. The iris is heavily flecked with silvery-gold, with a pale gold inner ring in Wollumbinia dorsii (vs a coppery-gold iris, with a pale inner ring and a prominent black spot either side that almost splits the iris in Wollumbinia latisternum).The plastron colouration in Wollumbinia dorsii becomes progressively darker with blackish mottling and blotching over time, often being almost entirely black in maturity. In Wollumbinia latisternum the plastron is more uniform cream to yellowish, with only a faint suffusion of dark grey and thin dark edging to the plastral and marginal shields. As mentioned above, there are also some superficial morphological similarities as well as significant differences between this new species and with populations of Wollumbinia bellii (Gray, 1844). In physical appearance Dorse’s Turtle shares some similarities with the usually larger Wollumbinia bellii. However, the carapace in Wollumbinia dorsii, although generally more rounded than in Wollumbinia latisternum, is much more so anteriorly than in Wollumbinia bellii, where the carapace tapers and narrows strongly anteriorly rather than presenting a smooth curve to the shell as in Wollumbinia dorsii or Wollumbinia latisternum. In Wollumbinia bellii, the rear marginals also flare slightly and are weakly serrated in mature specimens as in Wollumbinia dorsii (but the rear marginals tend to lack this posterior flaring in mature Wollumbinia dorsii); the body form is relatively deep in Wollumbinia dorsii (vs rather flat in Wollumbinia bellii). Interestingly, the carapace size, shape and marginal serration state of Wollumbinia dorsii is more similar to the Bald Rock Creek, Qld population of Wollumbinia bellii [Wollumbinia bellii dorriani (Wells 2002)] than it is to the condition found in the nominate populations of Wollumbinia bellii. Hatchlings of Wollumbinia bellii have the central shields of the carapace only slightly ridged (hatchling ridging stronger in Wollumbinia dorsii), and juveniles of Wollumbinia bellii have barely any serrations along the rear marginal shields (posterior marginals noticeably serrated in juvenile and immature Wollumbinia dorsii). The plastron of Wollumbinia dorsii is somewhat similar to that of Wollumbinia bellii in that the anterior plastral lobes extend to the edge of the carapace or slightly beyond and are broad and rounded in mature specimens of both species, However, the posterior of the plastron is straighter and slightly more tapered into the anal shield in Wollumbinia bellii than is the case in Wollumbinia dorsii. Additionally, in all populations of both Wollumbinia bellii bellii and Wollumbinia bellii dorriani, the anal shields are usually the longest, whereas in Wollumbinia dorsii the pectorals are the longest. As in Wollumbinia dorsii, the colour and patterning of Wollumbinia bellii can be rather stunning when young but the brighter, lighter colouration and patterning of juveniles becomes much reduced with age in both species. Both species when mature may become almost entirely black over the carapace and plastron, with only faint traces of their younger patterning of radially black blotching on a brown base once maturity is attained. In colouration juveniles of Wollumbinia dorsii have distinctive a pale reddish-brown carapace that is heavily flecked and blotched with black, and the plastron is creamish-yellow. The head is dark brown, with fine black reticulations or fleck; the mandibles are pale creamish, and this is continuous with a short yellowish line or stripe that extends to the posterior of the head – or occasionally continued further as a broken stripe on part of the lower neck. These colours gradually darken with age, with the dorsum of the carapace becoming a richer brown in sub-adults, with the edges of the plates being edged with black lines; many specimens can have black spotting or streaks as well. The plastron gradually darkens with increasing suffusions of black, to become almost completely black by maturity. In Wollumbinia bellii, juveniles are similarly brightly coloured, with the carapace being brown with dark greyish mottling. There is a light yellow neck stripe that extends from the back of the mouth (where it is widest) and, unlike Wollumbinia dorsii, it extends right along the lower lateral of the neck and through the tympanum to about the forelimb in Wollumbinia bellii - but with age, this stripe becomes much less distinctive. The gular region and ventral part of the neck is similar in colour to the neck stripe, sometimes vaguely mottled with greyish patches, but as males grow this neck stripe and under-body colour may take on a pinkish hue as well. The ventral part of the tail has a bright yellow hue as does the bridge between the carapace and plastron and some of the marginals (under-surface). In hatchlings, the plastron is yellowish (or sometimes a yellowishgreen) with extensive patches of dark grey throughout, and the limbs and exposed upper skin surfaces are steel-grey. By about 150 mm carapace length the plastral colour becomes progressively darker, with aged specimens being almost totally black ventrally as in Wollumbinia dorsii. Mature Wollumbinia bellii are similar to Wollumbinia dorsii in their tendency to become more melanistic with age. In Wollumbinia dorsii the pupil is black, with a silvery-gold iris delicately flecked with black, and a pale inner ring. The iris colour of Wollumbinia bellii on the other hand changes with age - hatchlings have an iris of golden yellow with brownish mottling, but may change to greyish-silver, with a variable pale inner ring, and a dark outer ring. Mature specimens of Wollumbinia bellii may also have a dull olivegreen iris, with a light inner ring and a darker outer ring, in marked contrast to the condition in Wollumbinia dorsii. The barbels are greyish to pale cream in both Wollumbinia dorsii and the nominate form of Wollumbinia bellii – however, the barbels are yellow in Wollumbinia bellii dorriani. A comparison of Wollumbinia dorsii with Wollumbinia purvisi (Wells and Wellington, 1985) or Wollumbinia georgesi (Cann, 1997) is hardly necessary given their morphological distinctiveness (see Cann, 1998; Wells 2007b). The unique presence of neural bones in Wollumbinia purvisi immediately separates this species from Wollumbinia dorsii. The upper neck is strongly covered in enlarged pointed tubercles in Wollumbinia dorsii a situation very different to that of Wollumbinia georgesi where the dorsum of neck skin is weakly covered with low tubercles. Further, the head shield or casque is patterned with paler markings and keratinised in surface texture in Wollumbinia dorsii, but the casque is smooth, and evenly dark-coloured in Wollumbinia georgesi a feature unique in the genus Wollumbinia with the exception of the similar situation in Wollumbinia purvisi [from WELLS 2009]. |
| Comment | Type species: Elseya latisternum Gray, 1867 is also the type species of the genus Myuchelys THOMSON & GEORGES 2009 (partly based on a phylogenetic analysis in GEORGES & THOMSON 2006). Elseya latisternum is the type species of the new genus Wollumbinia WELLS 2007. VAN DIJK et al. (2011) considered the genus Wollumbinia as a nomen illegitum. Synonymy: following Gray (1872), Boulenger (1889), Georges & Thomson (2010), and Fritz & Havas (2007). Kaiser et al. 2013 considered the generic name Wollumbinia Wells 2007 invalid and rejected its use instead of Myuchelys. |
| Etymology | The name is a combination of a contraction of the Aboriginal word for clear water, Myuna, and the Greek word for tortoises, chelys. It is a generalised reference to the types of habitat often preferred by the species of this genus. |
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