Meniscolophus

Meniscolophus Temporal range: Late Pliocene PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Infraclass:	Marsupialia
Order:	Diprotodontia
Family:	† Diprotodontidae
Genus:	† Meniscolophus Stirton, 1955
Species:	†M. mawsoni
Binomial name
†Meniscolophus mawsoni Stirton, 1955

Meniscolophus is an extinct genus of marsupial of the family Diprotodontidae. Only one species has been described, Meniscolophus mawsoni, from the Late Pliocene of the Tirari Desert, South Australia.

History and naming

The first remains of Meniscolophus were collected by a joint expedition between the South Australian Museum, Department of Geology of the University of Adelaide, and the University of California Museum of Paleontology in 1953. They were found in the Pliocene-aged Tirari Formation of Lake Palankarinna, South Australia. The fossils were subsequently described by Ruben A. Stirton in 1955, alongside other fossils collected during the expedition. The holotype is a mandible and left maxillary fragment belonging to the same individual. ^[1] Isolated teeth from the same locality have also been referred to this taxon. ^[2]

The genus name means "crescent crest" in Ancient Greek. The species name was chosen to honour Sir. Douglas Mawson, a former professor at the University of Adelaide. ^[1]

Description

The upper molar teeth of Meniscolophus have narrow V-shaped valleys that separate the protoloph from the metaloph. Both the second and third molars have expansions on the protoloph, with no expansions or ridges on the metaloph. Stylar cusps are entirely absent on the first lower and second upper molars. The labial surface on the first lower incisor is flat, while the anterior surface is convex. The lower third premolar lacks a hypoconid or talonid. A cingulum (shelf) runs from the labial (outwards, towards the cheek) side of the tooth's central cuspid down to its posterolingual base. The lower molars have crests that join cusps together (known as lophids) running across them. Descending from the anterolingual corner of the hypoconid is a metalophid, which blocks a valley near the midline of each tooth. In contrast to Zygomaturus , the labial cingulum is more extensive. ^[2]

Classification

In 1967, American palaeontologist Ruben A. Stirton divided Diprotodontidae into four subfamilies; Diprotodontinae, Nototheriinae (to which Meniscolophus was referred to), Zygomaturinae, and Palorchestinae. ^[2] This taxonomic grouping, however, wouldn't last long as Archer (1977) synonymised Nototheriinae with Diprotodontinae. ^[3] Archer & Bartholomai (1978) later recognised Meniscolophus as a diprotodontine. ^[4] In their 1984 book, Archer suggested that Meniscolophus and Euryzygoma might be congeneric. ^[5] The cladogram below shows its placement within Diprotodontinae and as sister taxon to Euowenia , from Black & Mackness (1999). ^[6]

Diprotodontoidea	Palorchestidae Diprotodontidae Diprotodontinae Ngapakaldia Pitikantia Bematherium Pyramios Meniscolophus Euowenia Euryzygoma Diprotodon Zygomaturinae Silvabestius Alkwertatherium Nimbadon Plaisiodon Kolopsoides Neohelos Kolopsis Maokopia Hulitherium Zygomaturus

Paleobiology

The Tirari Formation is Late Pliocene in age, with a date range of 3.9-3.4 Ma. It can be split into three main divisions: the basal Mampuwordu Member, the medial Main Body, and the overlying Pompapillina Member. Meniscolophus is known from the Palankarinna Fauna of the Mampuwordu Member. At the time, the area would have been a seasonally arid environment that may have housed fan-deltas, lakes and floodplains. ^{[7] [8]} Meniscolophus would have coexisted in this area alongside the diprotodontid Ambulator keanei , peramelemorphian Ischnodon australis and macropodine Prionotemnus palankarinnicus . ^{[7] [9]}

References

1. Stirton, R.A. (1955). "Late tertiary marsupials from South Australia". Records of the South Australian Museum. 11: 247–268.
2. Stirton, R.A.; Woodburne, M.O.; Plane, M.D. (1967). "Tertiary Diprotodontidae from Australia and New Guinea". Bureau of Mineral Resources, Geology and Geophysics, Bulletin. 85: 1–149.
3. Archer, M. (1977). "Origins and subfamilial relationships of Diprotodon (Diprotodontidae, Marsupialia)". Memoirs of the Queensland Museum. 18: 37–39.
4. Archer, M.; Bartholomai, A. (1978). "Tertiary mammals of Australia: a synoptic review". Alcheringa: An Australasian Journal of Palaeontology. 2 (1): 8. Bibcode:1978Alch....2....1A. doi:10.1080/03115517808619074.
5. Archer, M. (1984). "The Australian marsupial radiation". In Archer, M.; Clayton, G. (eds.). Vertebrate Zoogeography & Evolution in Australasia.(Animals in Space & Time). Hesperian Press: Carlisle. pp. 633–808.
6. Black, K. H.; Mackness, B. S. (1999). "Diversity and relationships of diprotodontoid marsupials". Australian Mammalogy. 21: 20–21.
7. Tedford, R.H.; Wells, R.T.; Barghoorn, S.F. (1992). "Tirari Formation and contained fossil faunas, Pliocene of the Lake Eyre Basin, South Australia". Records of the Northern Territory Museum of Arts and Sciences. 9: 173–194.
8. Nanson, G.C.; Price, D.M.; Jones, B.G.; Maroulis, J.C.; Coleman, M. (2008). "Alluvial evidence for major climate and flow regime changes during the middle and late Quaternary in eastern central Australia". Geomorphology. 101: 109–129. ISSN   0169-555X.
9. van Zoelen, J. D.; Camens, A. B.; Worthy, T. H.; Prideaux, G. J. (2023). "Description of the Pliocene marsupial Ambulator keanei gen. nov. (Marsupialia: Diprotodontidae) from inland Australia and its locomotory adaptations". Royal Society Open Science. 10 (5). doi:10.1098/rsos.230211. PMC   10230189 .