Litokoala
Encyclopedia
Litokoala is an extinct genus
of marsupial
, and along with Nimiokoala are closely related to the modern Koala
. The three genera may have diverged at an earlier date, although the drying of the continent and the expansion of Eucalyptus
forests towards the late Miocene may have delayed the evolution of cranial features unique to the modern genera. This indicates that either fossil genera could be an ancestor of the modern genus, or the modern genera has a common ancestor to both. More material needs collection to improve their taxonomical relationships. The genus lived about 10–16 million years ago in the middle Miocene Riversleigh
of Queensland. This area is described as a rainforest habitat at time of sediment deposition
. It exhibits a different diet to the modern species, with the dental symphysis
unfused, indicating a diet that was properly varied in nature, unlike the specialised nature of the genera Phascolarctos. The size is estimated to be only half of the modern genus. Cranial adaptions featured are in between the extant Common Brushtail Possum
and Koala with minor divergence from either. This genus and Nimiokoala are similar in most anatomical features so far as is known, except that the genus Litokoala contains superficial messateric process while Nimiokoala has "more marked basiooccipital
-basisphenoid
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. Ths basiocranial (back of skull) features are similar to Phascolarctos, while anterior (facial) of this the feature exhibit similarities with the genus Trichosurus. Only partial fragments of all collection are known, with only the posterior section from the Zygomatic process
known from L. kutjamarpensis's skull.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of marsupial
Marsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
, and along with Nimiokoala are closely related to the modern Koala
Koala
The koala is an arboreal herbivorous marsupial native to Australia, and the only extant representative of the family Phascolarctidae....
. The three genera may have diverged at an earlier date, although the drying of the continent and the expansion of Eucalyptus
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
forests towards the late Miocene may have delayed the evolution of cranial features unique to the modern genera. This indicates that either fossil genera could be an ancestor of the modern genus, or the modern genera has a common ancestor to both. More material needs collection to improve their taxonomical relationships. The genus lived about 10–16 million years ago in the middle Miocene Riversleigh
Riversleigh
Riversleigh, in North West Queensland, is Australia's most famous fossil site. The 100 km² area has fossil remains of ancient mammals, birds and reptiles of Oligocene and Miocene age...
of Queensland. This area is described as a rainforest habitat at time of sediment deposition
Deposition (geology)
Deposition is the geological process by which material is added to a landform or land mass. Fluids such as wind and water, as well as sediment flowing via gravity, transport previously eroded sediment, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of...
. It exhibits a different diet to the modern species, with the dental symphysis
Symphysis
A symphysis is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint.1.A symphysis is an amphiarthrosis, a slightly movable joint.2.A growing together of parts or structures...
unfused, indicating a diet that was properly varied in nature, unlike the specialised nature of the genera Phascolarctos. The size is estimated to be only half of the modern genus. Cranial adaptions featured are in between the extant Common Brushtail Possum
Common Brushtail Possum
The Common Brushtail Possum is a nocturnal, semi-arboreal marsupial of the family Phalangeridae, it is native to Australia, and the largest of the possums.Like most possums, the Common Brushtail is nocturnal...
and Koala with minor divergence from either. This genus and Nimiokoala are similar in most anatomical features so far as is known, except that the genus Litokoala contains superficial messateric process while Nimiokoala has "more marked basiooccipital
Occipital
The word occipital, in zoology, pertains to the occiput .Occipital is a descriptor for several areas of animal & human anatomy.*External occipital protuberance* Internal occipital crest* Greater occipital nerve...
-basisphenoid
Sphenoid bone
The sphenoid bone is an unpaired bone situated at the base of the skull in front of the temporal bone and basilar part of the occipital bone.The sphenoid bone is one of the seven bones that articulate to form the orbit...
flexion and a more extensive posterior attachment of the pterygoid
Pterygoid
Pterygoid can refer to:* Pterygoid processes of the sphenoid bone** The Lateral pterygoid plate by it* a muscle such as Lateral pterygoid muscle or Medial pterygoid muscle* a branch of the Mandibular nerve...
" (Louys et al., 2009, p. 989), which make these features basal in their taxonomical position in relation to the Phascolarctos. Ths basiocranial (back of skull) features are similar to Phascolarctos, while anterior (facial) of this the feature exhibit similarities with the genus Trichosurus. Only partial fragments of all collection are known, with only the posterior section from the Zygomatic process
Zygomatic process
Zygomatic process is a protrusion from the rest of the skull, like the bumper of a car. Most of it belongs to the zygomatic bone, and could therefore be called the zygomatic process of the zygomatic bone...
known from L. kutjamarpensis's skull.