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Etymology. — The name albagula is derived from the Latin adjective "alba" meaning
white (feminine) and the noun "gula" for throat, which is also feminine. Hence the name means "white
throat," and refers to the white or cream throat commonly seen in adult females of this species.
Related Taxa. — The affinities of E. albagula lie with a well-defined clade within
the E. dentata subgeneric group comprising E. irwini, E. lavarackorum, an
undescribed taxon from the Johnstone Rivers region of north coastal Queensland (Georges and Adams 1996),
and possibly New Guinean E. branderhorsti (Thomson, unpub. data, 1996), but excluding
E. dentata, E. novaeguineae, E. schultzei, an undescribed taxon from Arnhem
Land, and a number of other undescribed species from the New Guinea region.
We consider the closest living relative to be an undescribed taxon from the Johnstone Rivers region
near Cairns, but among described taxa, it is E. lavarackorum (White and Archer 1994) from the
Nicholson Drainage, Queensland, not E. irwini (Cann 1998) from the Burdekin River, Queensland.
DESCRIPTION
External Morphology
Carapace. — Carapace broadly oval posteriorly, blunt anteriorly
(Fig. 5). Marginals 2–6 upturned and marginals 7–11 expanded and flared laterally in adults. Adult
carapace is dark brown to black in color, often also heavily stained. Surface smooth, with or without
growth rings, and lacks luster.
Medial keels distinct on all vertebral and costal scutes of juveniles, forming a tricarinate ridged
carapace; keels indistinct or absent in adults. Carapace of juveniles serrated from the posterior edge
of marginals 1 (Fig. 6); young adults have a serrated margin from marginals 7. Spiny protrusions on
the ends of marginals (Fig. 1) present to ca. 120 mm carapace length. These features are thought to
derive from very rapid growth, and combine to make a very distinctive juvenile. Juvenile carapace tan,
mottled with dull brown to black in small juveniles, changing to dark brown or black at variable size
(in one case as small as 71 mm CL). Irregular mottling on each scute, concentrated as ragged blotches
on and straddling the sulci.
Plastron. — Plastral formula (using midline length) of the holotype:
fem>pec>abd>int>ana≥gul (Fig. 5), with no variation among the adult plastra examined.
Plastron narrow with axillary width ca. 50% of carapace width. Base of anterior lobe does not taper,
its lateral margins roughly parallel for the length of the pectoral. Bridge extensive and posterior
lobe longer than anterior lobe. Color of adult plastron often difficult to determine because of
complete staining to black, but base color cream to yellow, with or without darker streaks and
blotches. Axillary and inguinal scutes present.
Plastron yellow, mottled with indistinct black or brown, in some cases yielding a radial pattern in
the direction of scute growth. Mottling concentrated on bridge and posterior half of the plastral
surface. Inframarginal surfaces similarly mottled with irregular brown. Pale fields on inframarginals
tinged with pinkish orange. Pattern becomes indistinct and inframarginal surfaces lose pale fields
even in juveniles as small as 100 mm.
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Head and Soft Parts. — Head large, robust, but not to the extent of its nearest relatives
within the E. lavarackorum group; dark brown above, cream, yellow, or white below in females;
typically grey but occasionally cream below in males. Boundary between light ventral coloration and
darker dorsal coloration of head and neck very irregular, forming large, distinctive patches that
vary with age and among individuals (Fig. 7).
Tomial sheath of upper jaw yellow, cream, or grey, sometimes with vertical barring (Fig. 7). Head
shield entire, extending from immediately posterior to the nasals, over the parietal to the posterior
extent of the skull; deeply furrowed, involving both scutes and the bone beneath in large adults. Head
shield does not extend laterally to contact or approach the tympanum. Temporal region covered in
medium rounded hard scales. Two very prominent barbels on chin, rounded (not pointed) terminally;
cream, grey, and often suffused with pink in life; surrounded by small scales of low relief.
Boundary between pupil and iris indistinct (Fig. 7), occasionally with a vague lighter ring of gold
flecks around the pupil. Iris dull brownish olive, not bright; sclera brown; leading and trailing
eyespots absent. Upper eyelid with nine scales.
Dorsal surface of neck with medium rounded tubercles. Dark grey above, cream, yellow, or white below
in females, typically light grey below in males but also may be cream, yellow, or white below as in
females. As with head, boundary between light ventral coloration and darker dorsal coloration
irregular and varies greatly among individuals. Limbs and tail dark grey above, light grey below with
or without irregular blotches (see allotype, Fig. 2). In some adult females, and rarely in males, the
distinctive light coloration of the ventral and lateral surfaces of the head and neck may extend down
the forelimbs. Five claws on the front feet; four on the rear. A series of enlarged scales present on
the leading and trailing edges of the lower limb; may be present on the thigh. Pre-anal glands absent.
Dorsal color of the head and soft parts of juveniles follows that of the carapace. Ventral base color
cream suffused vaguely with yellow or orange. Ventral surfaces of tail and hindlimbs noticeably
brighter, forelimbs duller; no distinct striping on limbs or tail. Most neck tubercles are pale olive.
A vague stripe extends from the angle of the mouth two-thirds of the way to the shoulder, including
the lower tympanum. Ventral surface of head and neck cream or yellow, with a slight gold or orange
suffusion on chin and gular region.
Size and Sexual Dimorphism. — This species is among Australia’s largest side-necked turtles,
with possibly only Elusor macrurus attaining a larger size (J. Cann, pers. comm., 1997).
Females grow to a larger size than males (females to 420 mm CL, Mary River [M. Dorse, pers. comm.,
2004]; males to ca. 300 mm). Largest examples in this study were a 418 mm female and a 275 mm male.
Males easily distinguished from mature females by a much larger tail (Figs. 1 and 2), as with all
shortnecked chelids, however, sex of animals up to 150 mm CL could not be determined with confidence.
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