Perameles bowensis

Introduction

Perameles bowensis, from the Pliocene of New South Wales, is one of the oldest and most primitive of the Peramelidae, the family to which most Australian bandicoots belong. Living species of Perameles (long-nosed bandicoots) include the rare Eastern and Western Barred Bandicoots and the more common Long-nosed Bandicoot.

Identification

Bandicoots and bilbies belong to the family Peramelidae. The subfamily Peramelinae includes species of Isoodon (short-nosed bandicoots) and Perameles (long-nosed bandicoots). Living species of Perameles include the Western Barred Bandicoot (P. bougainville), the Eastern Barred Bandicoot (P. gunnii), and the Long-nosed Bandicoot (P. nasuta) (Perameles eremiana, the Desert Bandicoot, is probably extinct). Perameles species have longer ears and longer, more pointed snouts than species of Isoodon and are more lightly built. Western and Eastern Barred Bandicoots have distinctive transverse bands across their rumps, while P. nasuta is a drab grayish brown (some individuals may have a faint barred pattern).

Perameles bowensis was smaller than the Pleistocene Perameles sobbei from Queensland, which is probably its closest relative. Other differences between Pliocene-Pleistocene Perameles species are seen in the upper dentition. Primitive features in P. bowensis, P. sobbei and the living P. bougainville include reduced metaconules on M3/ (the advanced condition being a metaconule almost as large as the protocone); and the lack of a posterior cingulum on M2-3/ in P. bowensis and P. sobbei, also seen in didelphoid marsupials and dasyuroids. The preprotocristra is connected to the anterolingual base of the protocone in these two species, also seen in primitive dasyuroids. Perameles bowensis is more basal than other species of Perameles in that the trough between upper stylar cusps B and D is poorly developed (from Price 2005).

Perameles bowensis is most closely related to the recently discovered Perameles sobbei, from the Darling Downs in southeastern Queensland. Another species of Perameles from the Pliocene, P. allinghamensis, is poorly known (the species erected on the basis of a single large, isolated upper molar) and its relationships to other Perameles species are uncertain (it may not even be a species of Perameles but a separate genus).

Habitat

The Bow sediments are identified as sandy river deposits. This part of eastern New South Wales during the Pliocene had many rivers forming large alluvial deposits. Early in the Pliocene, much of New South Wales, like the rest of Australia, was warm temperate eucalypt forest, and rainfall was high. During the latter part of the Pliocene the climate cooled and the region became drier.

Distribution

Perameles bowensis was found in a road cutting near the tiny town of Bow in eastern New South Wales.

Feeding and diet

Modern species of Perameles forage by digging for roots and herbaceous vegetation, or by hunting for insects and, occasionally, other small animals. Similarly, P. bowensisprobably ate invertebrates (adults and larvae), fruit, fungi and seeds, and may have included other small animals in its diet.

Life history cycle

Living species of Perameles occupy a variety of habitats (or did, before numbers declined and ranges contracted). They construct nests that are used as resting burrows by day, and feeding takes place mainly in the evening.

Perameles bowensis probably had a short pregnancy, like living species of Perameles. Some living bandicoots are pregnant for just 12 days, which is the shortest pregnancy known for any mammal.

Fossils description

The holotype of Perameles bowensis is held by the Australian Museum, Sydney.

Evolutionary relationships

The origins and relationships of bandicoots and bilbies have long been the subject of debate. They have both a polyprotodont dentition, as in marsupial carnivores, but a syndactylous foot, as in the mainly herbivorous diprotodontians. In addition to morphological studies, efforts are being made to sort out the problem using molecular techniques. One study using nuclear genes has found Notoryctemorphia (marsupial 'moles'), Dasyuromorphia and Peramelemorphia form a natural group, most closely related to Diprotodontia, with the South American Dromiciops the closest relative to the all-Australian group. Didelphimorphia, the most primitive South American marsupials, are at the base of the marsupial family tree.

Both of the living barred bandicoots are rare; P. bougainville is extinct on the mainland, living on offshore islands; and P. gunnii is critically endangered. P. nasuta, however, is common and widespread along the east coast of Australia. Perameles eremiana, the Desert Bandicoot from the arid zone of central and western Australia, is probably extinct (and possibly an invalid species). The Pig-footed Bandicoot, Chaeropus ecaudatus, was once included in Peramelinae (with reservations), but is now in its own family, Chaeropodidae.

Perameles bowensis and P. sobbei appear to be closely related, placed together at the base of the Perameles species complex.

References

• Groves, C. P. and Flannery, T. F. 1990. Revision of the families and genera of bandicoots. Pp. 1-11 in Seebeck, J. H., Brown, P. R., Wallis, R. L. and Kemper, C. M. (eds) Bandicoots and Bilbies. Surrey Beatty and Sons, Sydney.
• Meredith, R., Westerman, M., Case, J. A. and Springer, M. S. 2007. A phylogeny and timescale for marsupial evolution based on sequences for five nuclear genes. Journal of Mammalian Evolution 15, 1-36.
• Meredith, R., Westerman, M. and Springer, M. S. 2008. A timescale and phylogeny for 'Bandicoots' (Peramelemorphia: Marsupialia) based on sequences for five nuclear genes. Molecular Phylogenetics and Evolution 47, 1-20.
• Muirhead, J., Dawson, L. and Archer, M. 1997. Perameles bowensis, a new species of Perameles (Peramelemorphia, Marsupialia) from Pliocene faunas of Bow and Wellington Caves, New South Wales. Proceedings of the Linnean Society of New South Wales 117, 163-173.
• Order Peramelemorphia: bandicoots and bilbies. Pp. 166-192 in Strahan, R. (ed) The Mammals of Australia. Reed New Holland, Sydney.
• Pacey, T. L., Baverstock, P. R. and Jerry, D. R. 2001. Phylogenetic relationships of the Bilby, Macrotis lagotis (Peramelemorphia: Thylacomiyidae), to the Bandicoots - DNA sequence evidence. Molecular Phylogenetics and Evolution 21, 26-31.
• Price, G. J. 2005. Fossil bandicoots (Marsupialia, Peramelidae) and environmental change during the Pleistocene on the Darling Downs, southeastern Queensland, Australia. Journal of Systematic Palaeontology 2, 347-356.
• Westerman, M. and Krajewski, C. 2000. Molecular relationships of the Australian bandicoot genera Isoodon and Perameles (Marsupialia: Peramelina). Australian Mammalogy 22, 1-8.

Further reading

• Long, J. A. et al. 2002. Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years of Evolution. Johns Hopkins University Press, Baltimore, 240 pp.