''Litokoala'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

marsupial Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...

s, and along with '' Nimiokoala'', is closely related to the modern

koala The koala (''Phascolarctos cinereus''), sometimes inaccurately called the koala bear, is an arboreal herbivorous marsupial native to Australia. It is the only Extant taxon, extant representative of the Family (biology), family ''Phascolar ...

. The three genera may have diverged at an earlier date, although the drying of the continent and the expansion of ''

Eucalyptus ''Eucalyptus'' () is a genus of more than 700 species of flowering plants in the family Myrtaceae. Most species of ''Eucalyptus'' are trees, often Mallee (habit), mallees, and a few are shrubs. Along with several other genera in the tribe Eucalyp ...

'' forests towards the late Miocene may have delayed the evolution of cranial features unique to the modern genera. This indicates that either fossil genus could be an ancestor of the modern genus, or the modern genus has a common ancestor to both. More material needs collection to improve their taxonomical relationships. The genus lived around 16–10 million years ago in the middle Miocene Riversleigh of

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

. This area is described as a rainforest habitat at time of sediment deposition. It had a different diet to the modern species, with the dental

symphysis A symphysis (, : symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together o ...

unfused, indicating a diet that was properly varied in nature, unlike the specialised nature of ''Phascolarctos''. The size is estimated to be only half of the modern genus. Cranial adaptations are intermediate between the extant

common brushtail possum The common brushtail possum (''Trichosurus vulpecula'', from the Ancient Greek, Greek for "furry tailed" and the Latin for "little fox", previously in the genus ''Phalangista'') is a nocturnal, semiarboreal marsupial of the family Phalangeridae ...

and koala, with minor divergence from either. This genus and ''Nimiokoala'' are similar in most anatomical features so far as is known, except ''Litokoala'' possessed a superficial messateric process, while ''Nimiokoala'' had "more marked basio occipital-basi sphenoid flexion and a more extensive posterior attachment of the pterygoid",(Louys et al., 2009, p. 989) which make these features basal in their taxonomical position in relation to the ''Phascolarctos''. The basiocranial (back of skull) features are similar to ''Phascolarctos'', while anterior (facial) features exhibit similarities with the genus '' Trichosurus''. Only partial fragments are known, with only the posterior section of the

zygomatic process The zygomatic processes (aka. malar) are three processes (protrusions) from other bones of the skull which each articulate with the zygomatic bone. The three processes are: * Zygomatic process of frontal bone from the frontal bone * Zygomatic ...

known from the ''L. kutjamarpensis'' skull.

References

{{Taxonbar, from=Q6648651 Miocene mammals of Australia Prehistoric vombatiforms Miocene marsupials Koalas Prehistoric marsupial genera Riversleigh fauna Fossil taxa described in 1967