Cranial Anatomy of Oligo-Miocene Koalas (Diprotodontia: Phascolarctidae): Stages in the Evolution of an Extreme Leaf-Eating Specialization

  title={Cranial Anatomy of Oligo-Miocene Koalas (Diprotodontia: Phascolarctidae): Stages in the Evolution of an Extreme Leaf-Eating Specialization},
  author={Julien Louys and Ken P. Aplin and Robin M. D. Beck and Michael Archer},
ABSTRACT Partial crania of two fossil species of koala (family Phascolarctidae) from Oligo-Miocene deposits in the Riversleigh World Heritage Area, one referable to Litokoala kutjamarpensis and another to Nimiokoala greystanesi, are described. Comparison with the extant koala Phascolarctos cinereus and other diprotodontian marsupials reveals a high degree of similarity in basicranial morphology between fossil and modern phascolarctids but substantial differences in the architecture of the… 
A new family of diprotodontian marsupials from the latest Oligocene of Australia and the evolution of wombats, koalas, and their relatives (Vombatiformes)
It is suggested that the highly derived vombatids evolved from wynyardiid-like ancestors, and that scratch-digging adaptations evolved in vombatoids prior to the appearance of the ever-growing (hypselodont) molars that are a characteristic feature of all post-Miocene vombatid species.
Middle Miocene origins for tough-browse dietary specialisations in the koala (Marsupialia, Phascolarctidae) evolutionary tree: description of a new genus and species from the Riversleigh World Heritage Area
Dental specialisations of Stelakoala riversleighensis include a high molar crown, the presence of large accessory blades and cuspids, and the development of lingual ribs on the entoconid and metaconid, which may represent an early stage in the transition to a more fibrous, highly specialised diet in the evolutionary history of koalas.
Lekaneleo, a New Genus of Marsupial Lion (Marsupialia, Thylacoleonidae) from the Oligocene–Miocene of Australia, and the Craniodental Morphology of L. roskellyae, comb. nov.
The domestic cat-sized marsupial lion Priscileo roskellyae (Thylacoleonidae) from the Oligocene–Miocene of Australia is described, which is a relatively conservative taxon, exhibiting no discernible change over the same interval of time.
A new koala (Marsupialia:Phascolarctidae) from the late Oligocene Etadunna Formation, Lake Eyre Basin, South Australia
An isolated upper molar represents Litokoala thurmerae sp. nov., the eighth species of phascolarctid marsupial (koalas) from the South Australian mid-Tertiary sequence, and the fourth from the late
New genus of primitive wombat (Vombatidae, Marsupialia) from Miocene deposits in the Riversleigh World Heritage Area (Queensland, Australia)
A phylogenetic analysis incorporating the new genus of primitive wombat and using dental, cranial and postcranial characters as well as multiple outgroups indicates a sister relationship between the new taxon and R. crowcrofti relative to all other wombats.
Invictokoala monticola gen. et sp. nov. (Phascolarctidae, Marsupialia), a Pleistocene plesiomorphic koala holdover from Oligocene ancestors
Koalas (Phascolarctidae) are uncommon elements within the Australian fossil record. The earliest representatives are recorded from late Oligocene rainforest assemblages of central Australia. In
New Tertiary Koala (Marsupialia, Phascolarctidae) from Riversleigh, Australia, with a Revision of Phascolarctid Phylogenetics, Paleoecology, and Paleobiodiversity
The most plesiomorphic koala yet known, Priscakoala lucyturnbullae, is described and inclusion in the analysis of the enigmatic Pliocene genus Koobor, currently classified as Vombatiformes incertae sedis, indicates phascolarctomorphian affinities for the genus.
The Rise of Australian Marsupials: A Synopsis of Biostratigraphic, Phylogenetic, Palaeoecologic and Palaeobiogeographic Understanding
The origins, evolution and palaeodiversity of Australia’s unique marsupial fauna are reviewed. Australia’s marsupial fauna is both taxonomically and ecologically diverse comprising four extant orders
A Nearly Complete Juvenile Skull of the Marsupial Sparassocynus derivatus from the Pliocene of Argentina, the Affinities of “Sparassocynids”, and the Diversification of Opossums (Marsupialia; Didelphimorphia; Didelphidae)
It is agreed that the appearance of carnivorously-adapted didelphids in South America during the late Miocene, including sparassocynins, is likely related to a decline in diversity of the sparassodonts at this time, and that the disappearance of these carnivorous- adaptations at the end of the Pliocene may have been due to the arrival of placental carnivorans from North America.
Understanding morphological variation in the extant koala as a framework for identification of species boundaries in extinct koalas (Phascolarctidae; Marsupialia)
Aspects of cranial morphology, including a shortened robust rostrum and broad, irregular nasal aperture, confirm placement of Litokoala as sister taxon to the modern genus Phascolarctos, and suggest the possibility that L. dicksmithi was nocturnal, had enhanced visual acuity, and was a more agile arboreal species than the relatively sedentary extant koala.


Descriptions of koala fossils from the Miocene of Riversleigh, northwestern Queensland and implications for Litokoala (Marsupialia, Phascolarctidae)
The dentition of a partial skull of Litokoala from Jims Carousel Site, System C is described and it is suggested that the morphological variation between L. kutjamarpensis Stirton, 1967 and L. kanunkaensis Springer, 1987 does not warrant specific distinction.
The distribution of some basicranial characters within the Marsupialia and a phylogeny of the Phalangeriformes
Within the Phalangeriformes, phalangeroids and petauroids exhibit several derived characters not present in the macropodoids, which include modifications of the postglenoid process, the external auditory meatus, the ventral post glenoid foramen, and the bones of the auditory region of the skull.
The skull of Ekaltadeta ima (Marsupialia, Hypsiprymnodontidae?): An analysis of some marsupial cranial features and a re-investigation of propleopine phylogeny, with notes on the inference of carnivory in mammals
Preliminary results of investigation into dietary habitus indicate that Propleopinae represents a radiation of medium- to large-sized omnivorous kangaroos, and it is reiterated that a tendency toward carnivory might be inferred from the relative importance of high amplitude vertical shearing versus horizontal shearing and/or crushing elements in the dentition.
Patterns of evolutionary transformation in the petrosal bone and some basicranial features in marsupial mammals, with special reference to didelphids
Several basicranial regions support different clades within the Didelphidae that recent molecular work has identified, including a sister group relationship of Caluromys and CalurOMysiops, the monophyly of large opossums, a Lestodelphys-Thylamys clade, and a LmostodelPhys-ThYlamys-Gracilinanus-Marmosops clade.
The anatomy of the mammalian hand is exposed to an intriguing interplay between phylogeny and function, and provides insights on phylogenetic affinities as well as locomotory habits of extinct species, which proposes that the ancestor of extant vombatiforms (koalas and wombats) may have been arboreal.
Implications of Deltatheridium specimens for early marsupial history
The presence of specialized marsupial patterns of tooth replacement and cranial vascularization in Deltatheridium and the basal phylogenetic position of this taxon indicate that these features are characteristic of Metatheria as a whole.
Periotic Morphology in the Trichosurin Possums Strigocuscus celebensis and Wyulda squamicaudata (Diprotodontia, Phalangeridae) and a Revised Diagnosis of the Tribe Trichosurini
Comparisons with periotics of possums from the Tertiary Riversleigh deposits of Queensland suggest that, despite some similarities, the three extant trichosurins may be more closely related to each other than to the Riversleigh taxa.
Petrosals of Late Cretaceous marsupials from North America, and a cladistic analysis of the petrosal in therian mammals
ABSTRACT Ten isolated petrosals of Late Cretaceous marsupials belonging to three types—A, B, and C—are described from the Lance Formation of Wyoming and the Bug Creek Anthills of Montana. These are
The Evolutionary History and Diversity of Australian Mammals
The late Oligocene to middle Miocene record documents the highest levels of biodiversity known for the continent, comparabie to that which characterises the lowland rainforests of Borneo and Brazil, as well as dominated by bats and rhinolophoids.