Maximucinus

Maximucinus; Temporal range: Middle Miocene 14.2–12.9 Ma 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:	Dasyuromorphia
Family:	†Thylacinidae
Genus:	†Maximucinus
Species:	†M. muirheadae
Binomial name
	†Maximucinus muirheadae; Wroe, 2001

Maximucinus is an extinct genus of thylacinid that lived during the Middle Miocene in what is now Queensland, Australia. It is known only a second upper molar found at the Riversleigh World Heritage Area. It was the largest thylacinid of its time, attaining a body size of 18 kg (40 lbs). The genus is monotypic, containing only one species, Maximucinus muirheadae.

History and naming

Maximucinus was described as a new genus and species of thylacinid in 2001 by Stephen Wroe. The holotype and only known specimen, catalogued as QM F30331, is an isolated second upper molar. It was collected from the Ringtail site at the Riversleigh World Heritage Area, north-western Queensland.^[1] The site has been radiometrically dated to the Middle Miocene, ~14.2-12.9 Ma.^[2]

The genus name combines the Latin word maximus, large, with kynos, the Ancient Greek word for dog. The species name was chosen to honour fellow researcher Jeanette Muirhead, for their contributions towards the study of fossil thylacinids.^[1]

Description

Maximucinus is known only from a single specimen, an upper molar. Although the fossil material is scant, it has enough traits to differ it from all thylacinids. Stylar cusps B and D are well-developed. Furthermore, the aforementioned stylar cusps are compressed to the sides of the molar. The front most cingulum (a small shelf-like structure situated at the base of a tooth's crown) continues into the preparacrista. Both the protoconule and metaconule cusps are extremely small.^[1]

Wroe (2001) estimated its weight to be 18 kg (40 lbs), making it the largest thylacinid discovered from the middle Miocene.^[1]

Paleobiology

Fossils of Maximucinus are known only from a single site at Riversleigh, which dates to the Middle Miocene.^[1] The climate during the Middle Miocene would have been warm and permanently wet. Open rainforests would have covered the landscape at the time.^[2]^[3] Coexisting alongside Maximucinus would have been the thylacinids Muribacinus and Nimbacinus, and the thylacoleonids Wakaleo oldfieldi, W. vanderleueri and Lekaneleo myersi. The two families of carnivorous marsupials were likely able to coexist with one another due to differences in both body size and vertical habitat segregation.^[4]

The molar of Maximucinus shows some specializations towards hypercarnivory (i.e. minute protoconule and metaconule cusps), although it was clearly less specialised than that of later thylacinids as it still retains well-developed stylar cusps.^[5]

References

^ ^a ^b ^c ^d ^e Wroe, S. (2001). "Maximucinus muirheadae, gen. et sp. nov. (Thylacinidae : Marsupialia), from the Miocene of Riversleigh, north-western Queensland, with estimates of body weights for fossil thylacinids". Australian Journal of Zoology. 49 (6): 603–314. doi:10.1071/ZO01044.
^ ^a ^b Woodhead, J.; Hand, S.J.; Archer, M.; Graham, I.; Sniderman, K.; Arena, D.A.; Black, K.H.; Godthelp, H.; Creaser, P.; Price, E. (2014). "Developing a radiometrically-dated chronologic sequence for Neogene biotic change in Australia, from the Riversleigh World Heritage Area of Queensland". Gondwana Research. 29 (1): 153–167. doi:10.1016/j.gr.2014.10.004.
^ Travouillon, K.J.; Legendre, S.; Archer, M.; Hand, S.J. (2009). "Palaeoecological analyses of Riversleigh's Oligo-Miocene sites: implications for Oligo-Miocene climate change in Australia". Palaeogeography, Palaeoclimatology, Palaeoecology. 276 (1–4): 24–37. doi:10.1016/j.palaeo.2009.02.025.
^ Gillespie, A. K. (2023). "Two new marsupial lion taxa (Marsupialia, Thylacoleonidae) from the early and Middle Miocene of Australia". Alcheringa: An Australasian Journal of Palaeontology. 47 (4): 506–521. Bibcode:2023Alch...47..506G. doi:10.1080/03115518.2022.2152096. S2CID 256157821.
^ Rovinsky, Douglass S.; Evans, Alistair R.; Adams, Justin W. (2019-09-02). "The pre-Pleistocene fossil thylacinids (Dasyuromorphia: Thylacinidae) and the evolutionary context of the modern thylacine". PeerJ. 7: e7457. doi:10.7717/peerj.7457. ISSN 2167-8359. PMC 6727838.

[Wroe2001-1] Wroe, S. (2001). "Maximucinus muirheadae, gen. et sp. nov. (Thylacinidae : Marsupialia), from the Miocene of Riversleigh, north-western Queensland, with estimates of body weights for fossil thylacinids". Australian Journal of Zoology. 49 (6): 603–314. doi:10.1071/ZO01044.

[Woodhead14-2] Woodhead, J.; Hand, S.J.; Archer, M.; Graham, I.; Sniderman, K.; Arena, D.A.; Black, K.H.; Godthelp, H.; Creaser, P.; Price, E. (2014). "Developing a radiometrically-dated chronologic sequence for Neogene biotic change in Australia, from the Riversleigh World Heritage Area of Queensland". Gondwana Research. 29 (1): 153–167. doi:10.1016/j.gr.2014.10.004.

[T09-3] Travouillon, K.J.; Legendre, S.; Archer, M.; Hand, S.J. (2009). "Palaeoecological analyses of Riversleigh's Oligo-Miocene sites: implications for Oligo-Miocene climate change in Australia". Palaeogeography, Palaeoclimatology, Palaeoecology. 276 (1–4): 24–37. doi:10.1016/j.palaeo.2009.02.025.

[Gillespie2023-4] Gillespie, A. K. (2023). "Two new marsupial lion taxa (Marsupialia, Thylacoleonidae) from the early and Middle Miocene of Australia". Alcheringa: An Australasian Journal of Palaeontology. 47 (4): 506–521. Bibcode:2023Alch...47..506G. doi:10.1080/03115518.2022.2152096. S2CID 256157821.

[Rovinsky2019-5] Rovinsky, Douglass S.; Evans, Alistair R.; Adams, Justin W. (2019-09-02). "The pre-Pleistocene fossil thylacinids (Dasyuromorphia: Thylacinidae) and the evolutionary context of the modern thylacine". PeerJ. 7: e7457. doi:10.7717/peerj.7457. ISSN 2167-8359. PMC 6727838.

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