Mukupirna

Credit: Peter Schouten.

*Mukupirna* is an extinct genus of mukupirnid vombatiformes that lived in Southern and Central Australia during the Late Oligocene.

## History

*M. nambensis* was coined by Beck et al. (2020) and *M. fortidentatus* was coined by Crichton et al. (2023). The latter means "strong-toothed", referring to the robust incisors and anterior cheek teeth. The second species was justified by Beck et al. (2020)'s decision not to specify a gender for the name *Mukupirna*; the 2023 analysis follows ICZN article 30.2.4. in assuming that it is feminine due to the "-a" suffix. The type species was initially reported from Southern Australia, but the addition of *M. fortidentatus* in 2023 from Pwerte Marnte Marnte Local Fauna, Northern Territory, Central Australia extends the range of this genus. The holotype was recovered from two-tonne limestone blocks that were quarried from a 3x2 meter area during expeditions in 2014 and 2020. These were led by Aidan Couzens and Arthur Crichton, respective to each date, both of which are authors for the description publication. The rock was prepared 2020-2022 at Flinders University using etching as well as acetic acid and mechanical (eg. rock saws and pneumatic micro-jack tools) techniques, except for NTM P10438 and NTM P6371; collected by D. Megirian, P. Latz and H. Larson in 2005 and P. Murray, D. Megirian and J. & I. Archibald in 2003, respectively,

## Description

*Mukupirna* is characterized by roughly being the size of a grizzly bear and a suspected herbivorous diet. *Mukupirna* is known by a severally damaged mandible, with flat molars, several ribs and limb elements; such as claws and metatarsals. *Mukupirna* shows unusual diversity in vombatiformes, the group that contains *Diprotodon*, koalas and wombats. *Mukupirna* was around 100 kilograms heavy, a large size for a group of mainly small animals. *Mukupirma* shows evidence of scratch-digging, but not true burrowing. The type species is around 143-171 kilograms in weight, whereas *M. fortidentata* is around 48 kilograms.

*M. fortidentata* and *M. nambensis* have upper cheek teeth that are distinguished in the former through being proportionally wider in the anterior molars; an M1 anterior width with subequal length (by 12%), a steeper anteroposteriorly decreasing cheek tooth width by 20%; stronger bilobed upper cheek teeth; alignment of the P3 with the buccal cusps (rather than the lingual, as in *M. nambensis*) on the longitudinal axis of the occlusal view; the lacking of a diastema between the I3 and C1 (3.5 millimeters in *M. nambensis*); outwards-splaying molar roots in the direction of the maxilla/dentary (thus, the total alveolar rim width is 10% larger than the molar cown width, unlike the subequal condition of *M. nambensis*); and the lingual molar root faces are quite deeper at the dorsoventral concavity that is located midway down the root length.

Paratypes of *M. fortidentatus* are: NTM P11998 (partial premaxilla with partial I1-2), NTM P11999 (partial left maxilla with posterior portion of M1 and M2-3), NTM P12000 (left dentary with i1-m4), NTM P12001 (partial left dentary and very worn p3-m3), NTM P10438 (partial right dentary and worn p3-m4), NTM P12002 (right dentary with p3) and NTM P13257 (partial left dentary with i1, p3, m1 and lingual portion of m2). Referals to this taxon include: NTM P12003 (left maxilla fragment with partial P3 and M1), NTM P2815–11 (left m3), NTM P12004 (left p3), NTM P12005 (right m1), NTM P12006 (worn right m3), NTM P12007 (worn possible right m2), NTM P12008 (anterior portion of P3), NTM P12009 (posterior portion of P3), NTM P12010 (posterior portion of p3), NTM P12011 (anterior portion of m2, unworn), NTM P13261 (left I2), NTM P13262 (left P3), NTM P13263 (left I3), NTM P13264 (right I3), NTM P13348 (distal portion of left humerus), NTM P13347 (right pisiform), NTM P13346 (distal left tibia, damaged), NTM P13345 (right talus), NTM P13344 (left talus) and NTM P6371 (damaged right calcaneus).

## Classification

Crichton et al. (2023) analyzed 124 craniodental and 20 postcranial traits to classify enigmatic vombatoids. They recover a tree that includes *Marada* as the sister taxon to the *Mukupirna* spp. and Vombatidae clade. They find that *Mukupirna fortidentatus* lacks robust dentary synapomorphies with *Marada* that would, otherwise, suggest placement in a clade that excludes vombatids. They advocate for Beck et al's Mukupirnidae as distinguished from Maradidae. In addition, their study revealed morphologies consistent with acquiring and processing hard plants but strange among vombatiforms. The dental specimens of *M. fortidentatus* also allow for identification of other vombatoids from Australia, pushing the split date for vombatids to before 24 million years.

## Notable Specimens

* AMNH FM 102646 (prev. QMAM 16824): The holotype of *M. nambensis*, consisting of postcranial remains, like ribs, metatarsals, claws, and limb elements as well as cranial material.
* NTM P11997: A splanchocranium, dorsoventrally crushed, with left P3-M3 and right C1-M4. The type of *M. fortidentatus*.

## Paleoecology

The Pwerte Marnte Marnte locality (24°21′ South 133°43′ East) is located on the south flank of James Range, Northern Territory, Australia. Here produced the Pwerte Marnte Marnte Local Fauna, which is probably late Oligocene in age due to biochronological study. It has been suggested to predate the Etadunna and Namba Formations due to the state and progressive evolution of the marsupial taxa present within, and thus may be of a thus-unnamed land mammal age that precedes the Etadunnan. This locality produces fossils of *M. fortidentatus* as well as other marsupial taxa (including vombatoids, several indeterminate but informative). Very distorted and fractured skeletal elements are produced by the locality in 0.5-1-meter-thick calvareous limestone conglomerate, many which bone fragments are nondiagnostic and surrounded by rounded (mostly) quartz pebbles. Poorly defined depositional layers are found, and loosely delineate by pebble and bone fragment density. In each layer are heavily mixed fossils and association between elements is not found. However, the data provided by the site suggests that it only preserves a single fauna, mainly due to overlap in faunal elements between depositional layers.

## References

* http://novataxa.blogspot.com/2020/06/mukupirna.html
* https://www.tandfonline.com/doi/full/10.1080/03115518.2023.2181397