Hypsiprymnodon and Potorous: living ancestors for Adalatherium and Vintana in the LRT

Late Cretaceous Madagascar
was THE place to be, now isolated from India, Africa, Australia and Antarctica. Adalatherium (Figs 1, 2), the ‘crazy beast’ lived there then. Scientists classified it as a member of the ‘Gondwanatheria‘, intended to be a pre-mammal clade. Unfortunately, members have been bounced around, but never in the direction the LRT now nests them.

The same can be said of its coeval, but larger, neighbor, Vintana (Fig 2), currently known from just a large, odd skull with descending flanges on its jugals = zygomatic arches = cheek bones.

Recent housekeeping in the LRT
moved Adalatherium and Vintana (Figs 1, 2) from paeodotheres and interatheres (= extinct marsupials with deep cheekbones) to basal kangaroos like Potorous and Hypsiprymnodon (Figs 1, 2), keeping it simple.

The deep cheekbones of Vintana turned out to be convergent traits, developed in isolation on Madagascar.

So there’s no need to invent new clades.
These two Late Cretaceous ‘engimas’ are just basal quadrupedal kangaroos. Just add these taxa to your own studies to confirm, refute or modify this hypothesis of interrelationships. The LRT minimizes taxon exclusion by including so many (2324) taxa.

Can you see the family resemblance?
If not, let us know which taxa are closer in morphology.

This interrelationship with kangaroos documents the antiquity of Marsupialia, predating the splitting of Madagascar from Australia.

Adalatherium hui
(Krause et al. 2020; Late Cretaceous) was originally considered a relative of multituberculates, but here nests with Dactylopsila, an extant striped opossum with similarly large incisors.

Vintana sertichi
(Krause et al. 2014; Late Cretaceous, UA 9972; 12.4 cm skull length; is a Madagascar mammal originally considered a member of the Allotheria and Gondwanatheria, two clades that do not appear in the large reptile tree. The LRT nests Vintana with basal quadrupedal kangaroos, like Potorous and Hypsiprymnodon.

Krause et al reported, “The new taxon is the largest known mammaliaform from the Mesozoic of Gondwana. Its craniofacial anatomy reveals that it was herbivorous, large-eyed and agile, with well-developed high-frequency hearing and a keen sense of smell. The cranium exhibits a mosaic of primitive and derived features, the disparity of which is extreme and probably reflective of a long evolutionary history in geographic isolation.”

References
Krause DW et al. 2014. Vintana sertichi (Mammalia, Gondwanatheria) from the Late Cretaceous of Madagascar. Journal of Vertebrate Paleontology Memoir 14. 222pp.
Krause DW et al (10 co-authors 2020. Skeleton of a Cretaceous mammal from Madagascar reflects long-term insularity. Nature. 581 (7809): 421–427. doi:10.1038/s41586-020-2234-8

wiki/Adalatherium
wiki/Vintana
wiki/Gondwanatheria

Vintana: a weird wombat, not an ‘allothere’

Vintana and the vain search for the clades Allotheria and Gondwanatheria