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Diversity and evolutionary relationships of ilariids, wynyardiids, vombatids and related groups of marsupials
... The wynyardiid molar pattern is therefore tantalizingly intermediate between the selenodont and the lophodont pattern, both functionally and structurally. This observation, combined with the basically similar incisor and premolar morphology, is at least good reason for considering that Wynyardiidae may be the plesiomorphic sister-group of Diprotodontoidea, a conclusion accepted by Myers et al.(1999). Anyway, it is possibly appropriate that the name Namilamadeta comes from Aboriginal words meaning "changeling tooth" (Rich and Archer, 1979). ...
... Uncertain relationships are indicated by dashed lines.Each block represents a distinct species, and blocks that extend without breaks through more than one time period indicate apparently long-surviving species. AfterMyers et al. (1999). ...
... Mammal-bearing fossil deposits at Riversleigh in northwestern Queensland have provided a rich record of mammal evolution for the late Oligocene to middle Miocene of northern Australia (Archer et al. 1999). Early to middle Miocene mammal assemblages (Systems Band C of Archer et al. 1989Archer et al. , 1994a are particularly species-rich and have been interpreted to have accumulated in cool temperate rainforests (Archer et al. 1994b ). ...
... Aplin and Archer (1987) suggested that Koobor should be regarded as Vombatiformes incertae sedis until more complete fossil material is recovered. This classification has been followed by subsequent authors (e.g., Black, 1999;Myers et al., 1999;Long et al., 2002). Despite the absence of lower dentitions, Black et al. (2012a), in their phylogenetic analysis of Vombatiformes using cranio-dental material, found that Koobor consistently grouped within Phascolarctidae. ...
The modern Koala Phascolarctos cinereus is the last surviving member of a once diverse family Phascolarctidae (Marsupialia, Phascolarctomorphia). Nine genera and at least 16 species of koala are known. Late Oligocene sediments of central Australia record the oldest fossils and highest species diversity. Five species are known from the early to middle Miocene rainforest assemblages of the Riversleigh World Heritage Area, Queensland. With the onset of dryer conditions after the middle Miocene climatic optimum (~ 16 Ma), rainforest habitats contracted resulting in the apparent extinction of three koala lineages (Litokoala, Nimiokoala, Priscakoala). Phascolarctos first appears in the fossil record during the Pliocene and the modern species around 350 ka. Despite a dramatic decline in taxonomic diversity to a single extant species, the fossil record indicates that at most only three koala species coexisted in any given faunal assemblage throughout their 24 million year history. Within these assemblages, the vast majority of extinct koalas are extremely rare (some known from only a single specimen) which may reflect a general rarity within their palaeohabitats compared with the modern species which is represented by an estimated 400,000 individuals spread over most of eastern mainland Australia. Be that as it may, Phascolarctos cinereus, although once geographically more widespread, occurring for example in Western Australia in the Pleistocene, underwent significant range contractions and localized population extinctions during the stressful climatic conditions of the late Pleistocene and more recently through human-induced habitat destruction. Combined with threats of disease, reduced genetic diversity and climate change, the survival of this iconic Australian marsupial is arguably a cause for concern.
... They suggested that Koobor species might represent the plesiomorphic sister group of wynyardiids plus ilariids and may be better placed in a separate vombatiform family. Aplin and Archer (1987) placed Koobor in Vombatiformes incertae sedis, noting that further resolution of its position requires discovery of more complete fossil material, a conclusion supported by subsequent authors (e.g., Black, 1999; Myers et al., 1999; Long et al., 2002). In this study, Koobor consistently grouped within Phascolarctidae rather than Vombatomorphia as the next most basal phascolarctid after Priscakoala (Fig. 2B). ...
Here we describe the most plesiomorphic koala yet known. Priscakoala lucyturnbullae, gen. et sp. nov., is the fourth and largest koala species described from Miocene deposits in the Riversleigh World Heritage area, northern Australia. It is known from a maxilla with M1–3 and isolated M2, M3 or M4 and m1. Relationships within the diprotodontian suborder Vombatiformes are clarified using cranial and dental characters based on a data set compiled from new and more complete cranial materials for each of the respective vombatiform families. Monophyly of Phascolarctidae is supported by the development of a protostylid and metastylid on m1. Priscakoala lucyturnbullae is the most plesiomorphic phascolarctid. Inclusion in the analysis of the enigmatic Pliocene genus Koobor, currently classified as Vombatiformes incertae sedis, indicates phascolarctomorphian affinities for the genus.
The late Oligocene taxa Marada arcanum and Mukupirna nambensis (Diprotodontia, Vombatiformes) are the only known representatives of the families Maradidae and Mukupirnidae, respectively. Mukupirna nambensis was described from a partial skeleton, including a cranium but no dentary, and reconstructed as the sister taxon to Vombatidae (wombats). By contrast, Ma. arcanum is known only from a single dentary, preventing direct comparison between the two. Here, we describe a new species, Mu. fortidentata sp. nov., based on craniodental and postcranial specimens from the Oligocene Pwerte Marnte Marnte Local Fauna, Northern Territory, Australia. Phylogenetic analysis of Vombatiformes, using 124 craniodental and 20 postcranial characters, places these three species within Vombatoidea, wherein Marada arcanum is sister to species of Mukupirna + Vombatidae. Mukupirna fortidentata sp. nov. does not share any robust synapomorphies of the dentary with Ma. arcanum that would support placing them together in a clade to the exclusion of Vombatidae. We therefore maintain separation of the families Mukupirnidae and Maradidae. From a functional perspective, the craniodental specimens of Mu. fortidentata sp. nov. reveal a suite of morphological traits that are unusual among vombatiforms, which we interpret as adaptations for acquiring and processing hard plant material. These include: a short, broad rostrum; large, robust, steeply upturned incisors; and a steep, anteroposteriorly decreasing gradient in cheek tooth size. The dental specimens of Mu. fortidentata sp. nov. also assist in the identification of two further allied taxa: an early vombatid from the younger late Oligocene Tarkarooloo Local Fauna, South Australia; and a possible vombatoid from the earliest Miocene Geilston Bay Local Fauna, Tasmania. The Tarkarooloo Local Fauna taxon indicates that vombatids diverged from other vombatoids prior to 24 million years ago.
Arthur I. Crichton [arthur.crichton@flinders.edu.au], College of Science and Engineering, Flinders University, Bedford Park, Adelaide, 5042, South Australia;
Trevor H. Worthy [trevor.worthy@flinders.edu.au], Aaron B. Camens [aaron.camens@flinders.edu.au], Adam Yates [Adamm.Yates@magnt.net.au] Museum and Art Gallery of the Northern Territory, Alice Springs 0870, Northern Territory, Alice Springs, 0870 Australia;
Aidan M. C. Couzens [acouzens@ucla.edu], Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA;
Gavin J. Prideaux [gavin.prideaux@flinders.edu.au], Flinders University School of Biological Sciences, Palaeontology, Adelaide, 5001 Australia.
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 Dasyuromorphia, Peramelemorphia, Notoryctemorphia and Diprotodontia) and one extinct order Yalkaparidontia). Molecular divergence dates estimate a Palaeocene origin for the Australian marsupial
orders yet ordinal differentiation is obscured by significant gaps in the fossil record with a single terrestrial mammal-bearing deposit known between the late Cretaceous and the late Oligocene. This deposit, the 55 million-year-old early Eocene Tingamarra Local Fauna of southeastern Queensland, contains Australia’s oldest marsupial (Superorder Australidelphia) as well as taxa tentatively interpreted to represent South American groups (Order Polydolopimorphia). Palaeobiogeographic hypotheses regarding the distribution and interordinal relationships of Australian and South American marsupials are discussed. Dasyuromorphia and Peramelemorphia were possibly also present in the early Eocene, Diprotodontia in at least the late Oligocene
and Notoryctemorphia and Yalkaparidontia in the early Miocene. Palaeobiodiversity was highest during the early to middle Miocene as evidenced by a spectacular array of marsupial groups in the rainforest assemblages of the Riversleigh World Heritage Area. The onset of icehouse conditions during the middle Miocene saw significant faunal turnover with loss of many archaic groups and the emergence of a range of modern lineages. Few deposits of late Miocene age are known. Development of Australia’s first grasslands and arid habitats occurred in the Pliocene, accompanied by an explosive radiation of grazing kangaroos. The Pleistocene was characterised by severe and unpredictable climatic conditions and the extinction of
the Australian megafauna. Lowered sea levels allowed faunal interchange between mainland Australia and neighbouring New Guinea as well as the arrival of the first humans. Resolution of the role of humans and/or climate change in megafaunal extinction requires more precise dating of late Pleistocene deposits. We reflect on the predictive power of the fossil record to enhance understanding of the effects of climate change and humans on the future of the Australian marsupial fauna.
AUSTRALIA'S second Mesozoic mammal, Kollikodon ritchiei
(Monotremata, Kollikodontidae, new family) has an extreme bunodont molar morphology.
The existence of two distinctively different families of monotremes in the Early
Cretaceous suggests that the order originated long before the Cretaceous and was
very diverse in at least the Australian portion of eastern Gondwana. With four
families now known from Australia, it is probable that monotremes originated and
diversified in the Australian/Antarctic sector of Gondwana, followed by a single
dispersal (ornithorhyn-chid) to the South American sector before or during the early
Paleocene. It is probable that kollikodontids are the sister-group of a
steropodontid/ornithorhynchid/tachyglossid clade. K. ritchiei and
Steropodon galmani are among the largest Mesozoic mammals known.
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