Acrobates frontalis De Vis, 1887

Acrobates frontalis De Vis, 1887

Recommended common name. Broad‐toed feather‐tailed glider

Type specimens. Syntypes QM J568 , 569 (F), 570, three spirit preserved thinly furred pouch young, collected by Mr Kendall Broadbent in the vicinity of Herbert Vale on the Atherton Tableland of north Queensland. According to De Vis (1887: 1134) “ Three specimens caught in the same tree … all three of the same age and size”; the three are clearly non-independent siblings taken from a nest . QM J12569 has had the skull removed but this was not located in the QM collection; it may have been sent to Oldfield Thomas in London and formed the basis of his margin annotation regarding examination of a syntype in October 1916 .

Diagnosis. Tail with terminal 2–3 mm unfurred ventrally, naked skin forming a prehensile pad ( Fig 3B View FIGURE 3 ); terminal pads of pedal digits 4 and 5 broadly heart-shaped, much wider than long and with broad distal groove; base of hallux with a single raised pad bearing striae ( Fig. 3D View FIGURE 3 ); tail fringe usually lacks pale emargination; ventral fur usually white or cream to roots, occasional individuals with grey-based fur in groin through to lower abdomen ( Fig. 4 View FIGURE 4 ). The ear canal disc occupies between 70 and 90% of the tympanic canal, has a raised narrow central ridge from the base that projects between 50 and 80% of the width of the disc, with the interior of the disc being depressed so that the margin appears raised. The disc in the internal view has sculpturing that emphasises the raised margin ( Fig. 5 View FIGURE 5 ).

Description. Body measurements based on mature adults are presented in Table 3 View TABLE 3 . Small body size, up to 92 mm head-body length. Flanks with a narrow patagium, running along the limbs and flank from the elbow to the knee.

Soft and silky fur, greyish brown dorsally. Ventral fur usually white or cream to roots, occasional individuals with grey-based fur in groin through to lower abdomen ( Fig. 4 View FIGURE 4 A-D). Colouring sharply demarcated at the edge of the patagium.

Tail slightly longer than the head and body (mean = 1.2). Tail markedly distichous and oval in cross-section, with very short ashy-brown fur on the upper and lower surfaces, paler below than above. Tail with terminal 2-3 mm unfurred ventrally, naked skin forming a prehensile pad ( Fig. 3B View FIGURE 3 ). Broad fringe of stiff long hairs along each side (about 8 mm in length), tail fringe usually lacking pale emargination.

The eyes are large, dark and encircled with black fur. The rhinarium is naked, flesh coloured, and deeply cleft; the nostrils are lateral.

The ears are moderately large, flattened, oval, and moderately furred externally.

Long vibrissae, unusually numerous, extend from the snout, cheeks, and base of each ear with shorter vibrissae extending from chin.

Hands and feet brown above, feet well furred, hands thinly furred. Terminal pads of pedal digits 4 and 5 broadly heart-shaped, much wider than long and with broad distal groove; base of hallux with a single raised pad ( Fig. 3D View FIGURE 3 ). Claws thin and sharp, barely extending beyond the level of the pads.

Manual digits with relatively similar length in the following order 4>3>2>5>1. Palmar surfaces hairless, with four broad low pads, three at the base of the fingers and one at the base of the palm. Length of pedal digits in the following order 4>5>3>2>1. Plantar surfaces hairless with five small pads, four at the base of the toes and one at the base of the foot.

Mammary formula unknown.

Dentition diprotodont with a formula of I 3/1, C 1/1?, P 3/3? M 3/3 = 20+16=36, based on examination of three vouchers (ANWC M223, M2960, M298760).

Variation in cranial and dental morphology is illustrated in Fig. 6 View FIGURE 6 and Supplementary Fig. S2 View FIGURE 2 .

Distribution. Broadly distributed across forested and wooded regions of eastern Australia, including: the south-eastern corner of South Australia; Victoria with the exception of the Wimmera region; and the Great Dividing Range and its coastal drainages of New South Wales and Queensland, north to Cape Weymouth on the eastern side of Cape York Peninsula. Acrobates frontalis is regionally sympatric with A. pygmaeus throughout large areas of south-eastern Australia, with numerous instances of syntopy at the level of museum locational data ( Fig. 7 View FIGURE 7 , Supplementary Table S1 View TABLE 1 ).

Remarks. Even though the syntypes of A. frontalis are clearly non-independent pouch young, the key diagnostic features of the widespread taxon are evident, including the naked prehensile pad on the underside of the tail tip, the heart-shaped terminal pads on pedal digits 4 and 5, and the accessory striated pad at the base of the hallux. The tail was accurately described by De Vis (1887: 1135) —“The under surface of the tail is more scantily clothed with shorter white hair continued centrally to an eighth of an inch from the tip, and laterally nearly to the tip”. The patagium, noted as “rudimentary” by De Vis, is represented by a distinct skin fold that extends from the elbow to the knee. The stiffened hairs of the tail fringe, so characteristic of the adult animal, are undeveloped and the future fringe is evident only in the laterally divergent growth of some fine hairs in the basal portion of the tail. De Vis (1887: 1135) reported the accompanying Indigenous name of “cubbie-cubbie”.

The geographic range of A. frontalis in south-eastern Australia overlaps extensively with that of A. pygmaeus ( Fig. 7 View FIGURE 7 ). However, there are large areas where A. frontalis is the only species present: Queensland north of the McPherson and Border Ranges, coastal New South Wales north of the Wallamba River, the headwater catchments of the Murray River in north-eastern Victoria and southern New South Wales, and the middle reaches of the Murray between Swan Hill in north central Victoria and Renmark in South Australia.

Unfortunately, very few of the published studies of Acrobates were conducted in regions of exclusive occurrence. Among the few exceptions are Russell’s (1980) natural history observations on feather-tailed gliders in northern Queensland and studies that include feather-tailed gliders from the northern coast of New South Wales and south-eastern Queensland ( Kirk et al. 2000; Hackett & Goldingay 2001; Smith & Agnew 2002; Wormington et al. 2002, Goldingay et al. 2007).