The New Guinea giant kangaroo has been renamed the Nombe nombe . We say renamed because it was previously called Protemnodon nombe , as it was believed to be a species of the genus P rotemnodon , which used to live in Australia. Now, in a new study of the fossils, paleontologists have concluded that the species belongs to a genus that is unique to New Guinea.
In the early 1970s, two jaws of an extinct giant kangaroo were found. The then young researcher Tim Flannery, today a professor, named it Protemnodon nombe . The fossils were between 20,000 and 50,000 years old and came from the Nombe Rockshelter, an archaeological and paleontological site located in the mountains of central Papua New Guinea. Fossils of another kangaroo and giant four-legged marsupials called diprotodontids were also found at this site.
Now, a team of paleontologists from Flinders University in Adelaide (Australia) has re-examined the jaws of Protemnodon nombe and has concluded that the marsupial would not belong to the genus Protemnodon but would be a more primitive and unknown animal. . The molars of the renamed Nombe nombe are different from those of other known kangaroos in that they have curved crests.
Scientists believe that 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 that time, New Guinea and Australia were linked by a land bridge and the first Australian mammals, including megafauna, were able to migrate to the tropical forests of New Guinea. Later, the Torres Strait, which today separates the two territories, flooded, and the connection was interrupted, causing the animals to separate from their Australian relatives and evolve separately to adapt to the tropical conditions of New Guinea.
Nombe would be a descendant of one of these ancient kangaroo lineages, which went on to live in the rainforest and developed a thick jaw and strong chewing muscles. Thus it was able to feed on the hard leaves of trees and bushes.
There is still much to discover about this very special kangaroo, and the information we have is that which has been extracted from the two lower jaws that were found in the 1970s.
Megafauna did not only exist in Australia
The existence of all kinds of giant animals, called megafauna, in Australia is well known. Before becoming extinct some 40,000 years ago, these spectacular creatures shared space with typical Australian savannah animals such as kangaroos, koalas and crocodiles, but some of these were larger than they are today.
At that time, in Australia there were giant wombats called Phascolonus , 2.5-meter-tall short-faced kangaroos, and the 3-tonne Diprotodon optatum , considered the largest marsupial in history. Some members of the Australian megafauna such as the red kangaroo, the emu and the cassowary live today.
Megafauna also existed in New Guinea, but it is less studied than the Australian one. Fossils that have been thoroughly analyzed hint at the existence at that time of fascinating and unusual animals whose evolutionary histories are intertwined with those of Australia.
After the sporadic fossil excavations carried out in New Guinea by American and Australian researchers in the 1960s, 70s and 80s, in which remains of extinct megafauna were located, the last time the area has been explored was in the early 1970s. 90. The Flinders researchers aim to change this situation and plan to carry out three excavations at two different sites in Papua New Guinea in the next three years.
Reference: Kerr, I., Prideaux, G. 2022. A new genus of fossil kangaroo from late Pleistocene New Guinea. Transactions of the Royal Society of South Australia. DOI: https://doi.org/10.1080/03721426.2022.2086518
