Groeberia: no longer an enigma taxon and no longer an allothere

Wiikipedia reports,
Groeberiidae is a family of strange non-placental mammals from the Eocene and Oligocene epochs of South America. Chimento et al. 2013 determined that Groeberia was a member of the Allotheria, a mammal clade not recovered in the large reptile tree (LRT, 1013 taxa). Simpson & Wyss 1999, considered Groberia relatives to be diprotodontians (wombats), By contrast McKenna 1980 claiming that considering them metatherians was “an act of faith”. The LRT supports that nesting as Groeberia nests with Vintana, another former enigma, both within the Metatheria (marsupials).

Groeberia minoprioi (Patterson 1952,  MMP 738) and G. pattersoni (Simpson 1970) are best known from a tall and narrow anterior skull and mandibles (Fig. 1) with an unusual set of teeth.

Figure 1. Groeberia drawing, photo and color-coded bones and teeth. This taxon nests with Vintana in the LRT and that canine-ish tooth must be a premolar because canines are unknown in this clade going back several nodes.

Figure 1. Groeberia drawing, photo and color-coded bones and teeth. This taxon nests with Vintana in the LRT and that canine-ish tooth must be a premolar because canines are unknown in this clade going back several nodes. As in related taxa, the jugal contacts the premaxilla. The descending process on the jugal is just appearing here.

The large reptile tree (LRT, 1012 taxa) nests Groeberia with Vintana (Fig. 2) among the wombats.

Note the large gnawing incisors backed up by an long upper premolar in the place usually occuupied by a canine. The tooth is not a canine because no more primitive relatives have a canine. Not also the small bump below the jugal. This becomes much longer in relatives like Vintana.

Figure 1. Vintana as originally illustrated. I added colors to certain bones. Note the high angle of the ventral maxilla and the deep premaxilla. Lateral view reduced to scale with other views.

Figure 2. Vintana as originally illustrated. I added colors to certain bones. Note the high angle of the ventral maxilla and the deep premaxilla. Lateral view reduced to scale with other views.

References
Chimento NR, Agnolin  FL and Novas FE 2015. The bizarre ‘metatherians’ Groeberia and Patagonia, late surviving members of gondwanatherian mammals. Historical Biology: An International Journal of Paleobiology27 (5): 603–623. doi:10.1080/08912963.2014.903945]
McKenna MC 1980. Early history and biogeography of South America’s extinct land mammals.
Patterson B 1952. Un nuevo y extraordinario marsupial deseadiano. Rev Mus Mun Cienc Nat Mar del Plata. 1:39–44.

wiki/Groeberiidae

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