Pseudocheiridae

Class Mammalia Order Diprotodontia Family Pseudocheiridae

Thumbnail description

Medium-sized possums, most species rather slow-moving, with short limbs; their teeth, particularly molars, have selenodent (i.e., half-moon shaped) crests, ideal for cutting and grinding leaves; ears are small and furred, fur color is mostly brown or gray with the last part of the (prehensile) tail more or less hairless

Size

Number of genera, species

6 genera; 16 species

Habitat

Forests and woodlands, suburban areas

Conservation status

Vulnerable: 3 species; Lower Risk/Near Threatened: 4 species; Data Deficient: 3 species

Distribution

New Guinea, Australia including Tasmania

Distribution

New Guinea, Australia including Tasmania

Evolution and systematics

Pseudocheiridae are most closely related to Petauridae, and together they form a superfamily Petauroidea. Even though this superfamily is named after petaurids, the pseudocheirids are obviously the more primitive and generalized family. This is evident both from morphology and from paleontological data. Pseudocheirids have been found in very old Tertiary deposits. The oldest undoubtedly pseudocheirid known so far comes from the late Oligocene-middle Miocene, and those genera are already rather distinct from each other. Oligocene as well as Quaternary species have been found in several central Australian and Queensland records, which points to a wideranging distribution already there. These paleontological data, together with the fact that today only two genera (nine species) live in New Guinea, but six genera (seven species) live in Australia, suggest that the family had its origin in Australia and immigrated into New Guinea quite recently. Dental morphology of pseudocheirids is also considered rather primitive: The W-shaped molars are considered (Archer) as more primitive than the rounded cusps of petaurids. Even though koalas also have similar molar crowns, this is being regarded as a convergence due to leaf-eating. Both cytogenetic studies and al bumin microcomplement fixation techniques have yielded quite clear-cut results recently concerning taxonomy within the family. No subfamily has been erected, but Hemibelideus and Petauroides are closely related to each other, and only distantly related to the rest. Petropseudes and Pseudochirops similarly are separate from the rest, but also with a certain distance between the two genera. Pseudochirulus, which now contains several species previously assigned to Pseudocheirus, also is an isolated genus. Some of the species (e.g., P. peregrinus, Pseudochirulus canescens) are subdivided into up to six subspecies, which is further evidence for both long isolation and old radiations.

Physical characteristics

The greater glider Petauroides volans is quite distinct from the rest of the family. It possesses a gliding membrane from elbows to lower legs similar but convergent to Petaurus spp., and a bushy tail. Its ears are large, the fur is long and woolly, and varies from white or gray to dark brown, sometimes with tail and body being in different colors. Its size puts it apart, with up to 37.4 in (95 cm) head-to-tailtip, and a weight of 32.8-42.3 oz (930-1,200 g). The rest of the family, in exter-

A common ringtail (Pseudocheirus peregrinus) foraging in the trees at night. (Photo by E. R. Dessinger. Bruce Coleman, Inc. Reproduced by permission.)

nal appearance is rather similar. All have short, stocky limbs, short round ears, and tails that are bare at the lower side at least about the final third of their lengths. Many species have dorsal stripes, though these are not always clearly seen when the fur itself is rather dark. Fur colors differ from light gray/cream, to orange, to dark brown. One species is greenish due to a mix of yellow, black, and white hairs. Internally, all species (including Petauroides) have a large cecum for fermenting their leaf-based diet, and their cheek-teeth are formed in the shape of cutting edges, scissorlike, to both cut and grind xerophytic leaves (e.g., Eucalyptus, which at least some species can detoxify).

Distribution

Pseudocheirids obviously already were part of the Australian fauna in times when the Australian continent still rested in wetter climatic zones. Species existing then, similar to other families, were larger than today's representatives, reaching up to 33 lb (15 kg). With increasing aridification of the Australian continent, pseudocheirids withdrew to the still wetter areas, and today are restricted to coastal, or coast-near areas in the east, northeast, southwest and northwest of the continent, as well as Tasmania. New Guinea seems to have been invaded rather late, and the species there are mostly restricted to mountainous, i.e., central areas.

Habitat

Nearly all of the New Guinean species, except for two rather poorly known and obviously rare species (Pseudochiru-lus canescens, Pseudocheirus caroli), inhabit mountain forests, where they are rather abundant. All of them prefer primary forests except Pseudocheirus forbesi, who seem to be more adapted to secondary, i.e. disturbed forest areas. There are up to four sympatric species in certain New Guinean places, and in those communities there are clear niche-separations in size, ranging from 5.3 to 70.5 oz (150 to 2,000 g) and nesting habits (from tree-hollows to dreys to sleeping exposed on branches). In Australia, one species (Petropseudes dahli) is semi-terrestrial, preferring rocky areas in Northern Australia, two species are found in sclerophyll forests (P. volans and Pseudocheirus pere-

A green ringtail (Pseudochirops archeri) in the trees of Australia. (Photo by C. B. & D. W. Frith. Bruce Coleman, Inc. Reproduced by permission.)
A lowland ringtail (Pseudochirulus canescens) foraging at night in the Uplands Tropical Rainforest, northeast Queensland, Australia. (Photo by Frithfoto. Bruce Coleman, Inc. Reproduced by permission.)

grinus), and the rest are living in higher altitude rainforests of the Atherton Tableland. Contrary to New Guinea, these sym-patric species (which also are in part sympatric to some pha-langerid species) are all in the same size class, namely, in the 31.7-42.3 oz (900-1,200 g) range, and all except one, rest in tree-hollows. Supposedly, niche-differentiation must be along some other axes, one of them possibly activity—each species has characteristic times of emerging and returning from and to nests, the aspect of the nesting-tree, or size of the hollows. Among the sclereophyll forest-dwellers, Pseudocheirus peregri-nus has been able to adapt to suburban habitats, feeding on rosebuds and rose leaves in front- and backyards, and day-nesting under roofs.

Behavior

Pseudocheirids are among the most diverse of all possums in term of social organization. The rock ringtail (Petropseudes dahli) seems to live in long-term pairs with overlapping young, as they have been observed as pairs with a young-at-heel, and another smaller one riding on back. Lemuroid ringtails are long-term monogamous, perhaps with a potential to an expansion similar to P. dahli, P. peregrinus is reported as either pair- or family-living, with paternal care such as carrying grooming and defending young. Sleeping groups of adults of varying sexual composition have also been recorded. Most of the rainforest species and P. volans are solitary both while foraging and resting.

Deposit of feces on specific sites has been found in P. dahli, and a sternal gland is used by sternal rubbing in several species of Pseudocheirus. Acoustic communication seems to be of medium importance, with distress calls uttered by young in trouble, soft contact calls by family members of P. peregrinus, loud contact calls, possibly for spacing, as a "dusk" chorus of

P. forbesi, and vocal recall of young from dangerous situations in P. peregrinus. There is no evidence of territorial defense in any species, even the solitary ones, except a certain spatial distribution pattern of P. volans that is more evenly distributed than statistically expected from randomness. This suggests at least active avoidance, or perhaps some sort of defense. All

A coppery ringtail (Pseudochirops cupreus) foraging. (Photo by C. B. Frith. Bruce Coleman, Inc. Reproduced by permission.)
The lemuroid ringtail (Hemibelideus lemuroides) has long claws to help it cling to trees. (Photo by E. R. Degginger. Bruce Coleman, Inc. Reproduced by permission.)

species are mostly nocturnual. Pseudochirops archeri sometimes can be seen active during the day.

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