Long ago, almost until the end of the last ice age, a peculiar giant kangaroo roamed the mountainous rainforests of New Guinea.
Research published Thursday by myself and colleagues suggests that this kangaroo was not closely related to modern Australian kangaroos. Rather, it represents a previously unknown type of primitive kangaroo unique to New Guinea.
The Age of Megafauna
Australia used to be home to all kinds of giant animals called megafauna, until most of them became extinct about 40,000 years ago. These megafauna coexisted with animals we now consider typical of the Australian bush – kangaroos, koalas, crocodiles and the like – but many were larger species of these.
Giant wombats were mentioned Phascolonus2.5 meter high short-headed kangaroos and the 3 ton Diprotodon optatum (the largest marsupial ever). Some Australian megafauna species, such as the red kangaroo, emu and cassowary, even survive to this day.
The fossil megafauna of New Guinea is considerably less well studied than that of Australia. But despite being shrouded in mystery, New Guinea’s fossil record has given us hints of fascinating and unusual animals whose evolutionary stories are intertwined with those of Australia.
Paleontologists have made sporadic expeditions and fossil excavations in New Guinea, including excavations by American and Australian researchers in the 1960s, 1970s, and 1980s.
It was during an archaeological dig in the early 1970s, led by Mary-Jane Mountain, that two jaws of an extinct kangaroo were unearthed. A young researcher (now a professor) named Tim Flannery named the species Protemnodon name†
The fossils that Flannery described are about 20,000-50,000 years old. They come from the Nombe Rockshelter, an archaeological and paleontological site in the mountains of central Papua New Guinea. This site also yielded fossils of another kangaroo and giant four-legged marsupials called diprotodontids.
Read more: Meet the giant wombat relative who made his living in Australia 25 million years ago
An unexpected discovery
Flinders University Professor Gavin Prideaux and I recently examined the fossils of Protemnodon name and found something unexpected. This strange kangaroo was not a species of the genus protemnodon, who used to live all over Australia from the Kimberley to Tasmania. It was something more primitive and unknown.
In particular, his unusual molars with curved enamel combs set him apart from all other known kangaroos. We moved the species to a brand new genus unique to New Guinea and renamed it (very creatively) nombe nombe†
Our findings show: Nombe may have evolved from an ancient form of kangaroo that migrated from Australia to New Guinea in the late Miocene, about 5-8 million years ago.
At the time, the islands of New Guinea and Australia were connected by a land bridge due to the lower sea level, while today they are separated by the Torres Strait.
This “bridge” allowed early Australian mammals, including megafauna, to migrate into the rainforests of New Guinea. When the Torres Strait flooded again, these animal populations separated from their Australian relatives and evolved separately to match their tropical and mountainous New Guinea home.
We are now considering: Nombe to be the descendant of one of these ancient kangaroos genera. The stocky, muscular animal lived in a diverse mountainous rainforest with dense undergrowth and a closed canopy. It evolved to eat tough leaves from trees and shrubs, giving it a thick jawbone and strong chewing muscles.
The species is currently only known from two fossil mandibles. And there is much more to discover. did Nombe hopping like modern kangaroos? Why is it extinct?
As is typical of paleontology, one discovery raises a whole host of new questions.
Strange but familiar animals
Little is known of New Guinea’s endemic wildlife outside the island, although it is very strange and very interesting. Very few Australians have a good idea of what’s out there, just across the strait.
When I went to the Papua New Guinea Museum in Port Moresby early in my PhD, I was impressed by the animals I encountered. There are several living species of large, worm-eating, long-nosed echidnas – one of which weighs up to 15 kilograms.
Author provided
There are also dwarf cassowaries and many different species of wallaby, tree kangaroo and opossum not found in Australia – plus many more in the fossil record.
We tend to think of these animals as uniquely Australian, but they have other intriguing shapes in New Guinea.
As an Australian biologist, it is both strange and exciting to see these ‘Aussie’ animals evolved into new and strange shapes in a different landscape.
Exciting for me and my colleagues, nombe nombe could breathe new life into paleontology in New Guinea. We are part of a small group of researchers recently awarded a grant to conduct three excavations over the next three years at two different sites in eastern and central Papua New Guinea.
In collaboration with the curators of the Papua New Guinea Museum and other biologists, we hope to inspire young local biology students to study paleontology and discover new fossil species. If we’re lucky, there might even be a complete skeleton of it nombe nombe waiting for us.