Fossils found in central Australia have revealed a surprising link. Researchers have found that a tiny, 6-million-year-old wallaby, Dorcapsoides cowpatensis, is related to the quirky forest-wallabies now found only in New Guinea. Modern cousins hop through lush jungle, but Dorcapsoides cowpatensis lived in dry scrublands.
Millions of years ago, Australia and New Guinea formed a single landmass, when sea levels dropped during ice ages. That allowed animals like Dorcapsoides to roam freely. As sea levels rose, and a harsh, drier climate descended in Australia, New Guinea’s forest wallabies found refuge in tropical habitats. Their Australian counterparts went extinct.
Map of significant fossil localities of Dorcapsoides cowpatensis. Credit: Isaac Kerr
Unlike its modern relatives, Dorcapsoides lived in sparse woodlands at Cowpat Hill (thus the name) in the Northern Territory. It likely hopped swiftly from dense cover into open scrub to feed on leaves, fungi, and fruit. It is the third ancient wallaby of its kind discovered in Australia from the late Miocene to early Pleistocene era.
Dorcapsoides cowpatensis can give us clues of ancient Australia-New Guinea faunal exchange
Isaac Kerr and Gavin Prideaux from the Flinders University, Adelaide described the new species in their paper. “The [Dorcopsini] group has a patchy fossil record beginning on the Australian mainland in the upper Miocene. Two species of fossil dorcopsin have been described from Australia to date. Here we describe a third Australian species.”
“With the recognition of D. cowpatensis it is apparent there was continued presence of a dorcopsin species in central Australia into the latest Miocene” observed the researchers in their paper. “This raises the question: why are dorcopsins present in Australia in the late Miocene and early Pliocene and absent from ∼4.4 Ma (early mid-Pliocene) onwards?”
“Prolonged aridification would seem a possible cause, except that it is evident that early dorcopsins, thrived in late Miocene central Australia despite spreading aridity and open habitats. This is at odds with the wet, forested environments generally preferred by living dorcopsins. Given the small number of localities involved, taphonomy could also play a significant role. Clarification of this issue must await further exploration of the dorcopsin fossil record, particularly that from Pliocene Australia.”
The forest-wallaby genus Dorcopsini contains six species, all of which live in New Guinea. Modern forest-wallabies are charming, and have long, curved tails that act like a fifth limb. They are a bit odd too, with their sad, whippet-like faces. Their unusual appearance and behaviors are still shrouded in mystery. Fossil discoveries like D. cowpatensis are crucial for filling those gaps.