Fossilised Lower Jaw of Nimbacinus richi

Middle Miocene, 13 million years old

Bullock Creek, Northern Territory

Holotype, NTM P9216-4

Nimbacinus was an early member of the thylacine family, a family of marsupials made famous by the historic extinction of its last surviving member, the Tasmanian tiger, or thylacine (Thylacinus cynocephalus). The first Nimbacinus fossils, named Nimbacinus dicksoni, came from rocks dated 17 to 14 million years old from northwestern Queensland. Later this spectacular Nimbacinus jaw was found in 13 million year old limestone from Bullock Creek, a fossil site from the northern edge of the Tanami Desert in the Northern Territory. Some minor differences between the Bullock Creek jaw and those from Queensland led to MAGNT scientists to designate it the holotype (name-bearing specimen) of a new species, Nimbacinus richi. Other scientists doubt that the differences are significant enough to merit a new species but we simply don’t have enough fossils to decide whether the differences noted are simply part of normal within species variation or not.

Fossils from Bullock Creek are embedded in solid limestone that was laid down at the bottom of a series of spring-fed creeks and ponds in the middle Miocene Epoch, 13 million years ago. To extract the fossils the concrete-like limestone must be slowly digested in vats of weak acid over a period of several weeks, or months while the acid resistant fossils slowly emerge. The fossils that emerge are exquisitely preserved as shown by this specimen. The original bone has been stained dark grey-black by manganese-rich minerals while the teeth now resemble shining jet-black jewels.

Like the Tasmanian tiger, Nimbacinus richi was a carnivore with sharp teeth adapted for slicing flesh. It was distinctly smaller than its recently extinct cousin, and would have been about the size of a fox and consequently would have fed on smaller prey such as birds, lizards and small rat-sized mammals.