Groeberiidae

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Groeberiidae
Temporal range:
Ma
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Theriiformes
Family: †Groeberiidae
Patterson, 1952
Genera
Synonyms

Groeberidae

Groeberiidae is a family of strange non-

allothere clade Gondwanatheria.[1] However, the relationship of the type genus, Groeberia, to Gondwanatheria has been firmly rejected by other scholars.[2]

History

The type species,

G. G. Simpson in 1970, and is known from at least two specimens.[3] Both occur in the Divisadero Largo Formation deposits dating to the Eocene
.

Flynn & Wyss, 1999 would go on to describe the Oligocene species Klohnia charrieri, and Goin et al., 2010 the taxa Klohnia major, Epiklohnia verticalis and Praedens aberrans, all also dating to this epoch.[3]

Recently, Chimento et al. 2013 re-examined

allothere affinities. Other taxa were not included in this examination for so far unspecified reasons, rendering their status as part of the clade unknown.[1]

Classification

Gondwanatheria cladogram per Chimento et al., 2015.

For most of their history, groeberiids were thought to be

marsupials. Though currently represented only by shrew opossums, through most of the Cenozoic Paucituberculata also included a variety of rodent-like species, making this assessment somewhat sound.[3] However, this classification was provisory at best, as compared to other paucituberculates groeberiids were highly aberrant.[3][1] A few differing opinions included Simpson & Wyss 1999, which considered these animals to be diprotodontians, and Pascual 1994 and Simpson 1970, which saw them as Metatheria incertae sedis, both of which contested.[1]

More recently,

multituberculate, a group in which its "aberrant" attributes turned out to be fairly typical. Within Gondwanatheria, it stands in a fairly basal position, having diverged before the diverse sudamericids but after Ferugliotherium.[1]

Other groeberiids have not been included in this analysis; whereas they're gondwanatheres or paucituberculates is yet to be determined.

Well before this reassignment, Malcolm McKenna expressed doubts on a marsupial identity for groeberiids, claiming that considering them metatherians was "an act of faith".[4]

However, Zimicz & Goin (2020) claimed that the anatomy of the teeth of Groeberia supports the metatherian affinities of this taxon. The phylogenetic analysis conducted by these authors recovered Groeberia as the sister taxon of Vombatiformes within Diprotodontia, though the authors cautioned that these results are preliminary.[5]

Characteristics

Groeberiids possess robust, deep snouts bearing elongated incisors and

hypsodonty and are thought to be grazers.[3]

Ecology

Groeberiids co-existed with a variety of other mammal groups, such as

meridiungulates and xenarthrans. The first South American caviomorph rodents are thought to have arrived to the continent roughly at the time these gondwanatheres were alive; competition, if any, between both groups is so far unresolved, though groeberiids are speculated to have been fairly specialised.[1] Assuming the genera besides Groeberia are in fact groeberiids, the group achieved its highest diversity in the mid-Oligocene, well after rodents arrived.[3]

Notes

  1. ^ When Chimento et al. 2013 was written, Vintana still lacked a binomial name, so it is referred to as "the Malagasy skull" in the paper.

References

  1. ^
    S2CID 216591096
    .
  2. S2CID 230968231
    .
  3. ^ a b c d e f Goin, F.J., Abello M.A. & Chornogubsky L. 2010. Middle Tertiary marsupials from Central Patagonia (Early Oligocene of Gran Barranca): Understanding South America’s Grande Coupure. En: Madden R.H., Carlini A.A., Vucetich M.G. & Kay R.F. (Eds.), The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic of Patagonia. Cambridge University Press.
  4. ^ McKenna, M.C., 1980. Early history and biogeography of South America's extinct land mammals.
  5. S2CID 213546042
    .
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