“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.
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.
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 Paleobiology. 27 (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.