Impidens

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Impidens
Temporal range: Late Anisian–early Ladinian, possibly early Carnian
Impidens.jpg
Impidens hancoxi
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Family: Trirachodontidae
Genus: Impidens
Tolchard, Kammerer, Butler, Hendrickx, Benoit, Abdala, & Choiniere, 2021
Type species
Impidens hancoxi
Tolchard, Kammerer, Butler, Hendrickx, Benoit, Abdala, & Choiniere, 2021

Impidens [lower-alpha 1] is an extinct genus of large omnivorous cynodont from the Triassic of South Africa and Antarctica. Its type and only species is Impidens hancoxi. [lower-alpha 2] Impidens inhabited high-latitude environments of southern Gondwana during the Middle Triassic, where it was probably the apex predator.

Contents

History

A specimen of Impidens was collected from Antarctica in 1986. In 1995, it was described as an indeterminate diademodontid possibly belonging to Titanogomphodon . [2] The holotype of Impidens hancoxi was found in South Africa in 2014. [3] It was described as a new species in 2021, with the Antarctic specimen and a less complete specimen from South Africa being referred to the species. [1]

Description

Impidens was one of the largest non-mammalian cynodonts, with a skull well over 400 millimetres (16 in) long, though the herbivorous Scalenodontoides from the Late Triassic was even larger. [4]

Classification

Impidens is a member of Trirachodontidae, a family of gomphodont cynodonts. It is closely related to its smaller contemporary Cricodon as well as the earlier Langbergia and Trirachodon . [5] However, the phylogeny of Trirachodontidae is not well-understood, and the family may be paraphyletic, with some species more closely related to traversodontids than others.

Paleoecology

Impidens fossils are known from the Cricodon-Ufudocyclops subzone of the Cynognathus Assemblage Zone of the Beaufort Group in South Africa and the upper Fremouw Formation in Antarctica. The dating of these strata is controversial; they are conventionally regarded as Middle Triassic in age, probably late Anisian or early Ladinian, but a biostratigraphically correlated fauna in South America has been dated to the beginning of the Late Triassic, in the early Carnian. [6] However, another biostratigraphically correlated fauna in China has been dated to the Anisian, suggesting the traditional dating may be correct. [7]

Impidens was probably the apex predator of its environment, as the only other large predator known to have coexisted with it was the somewhat smaller cynodont Cynognathus . The known large herbivores of the fauna are the cynodont Diademodon and the dicynodont Ufudocyclops . A smaller trirachodontid, Cricodon , was also present in the environment.

The Cricodon-Ufudocyclops subzone was deposited in a meandering river environment, with a deep channel and high banks. [8] Both it and the Fremouw Formation were high-paleolatitude environments, which may explain some of the faunal differences between them and lower-paleolatitude fauna. [4]

Footnotes

  1. From the isiZulu impi "combat" and the Latin dens "tooth" [1]
  2. Named in honor of Dr. John Hancox, a pioneering researcher of the strata it was found in. [1]

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<span class="mw-page-title-main">Cynognathia</span> Clade of cynodonts

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<i>Tropidostoma</i> Assemblage Zone

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<i>Lumkuia</i> Extinct genus of cynodonts

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<span class="mw-page-title-main">Diademodontidae</span> Extinct family of cynodonts

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Scalenodontoides is an extinct genus of Traversodontidae, a family of herbivorous cynodonts. It lived during the Late Triassic in what is now South Africa. Its type species is Scalenodontoides macrodontes. It was named in 1957 by A. W. Crompton and F. Ellenberger. Arctotraversodon plemmyrodon was originally classified as a species of Scalenodontoides, but was given its own genus in 1992. It is found in the Scalenodontoides Assemblage Zone of the Elliot Formation, which is named for it. It is one of the geologically youngest traversodontids, alongside the putative traversodontid Boreogomphodon. It is closely related to Exaeretodon and Siriusgnathus, but is distinguished by the presence of a shelf-like expansion of its parietal called the nuchal table. Though the largest known complete skull is only 248 millimetres (9.8 in) long, it may have been the largest non-mammalian cynodont, as an incomplete snout would have belonged to a specimen with an estimated skull length of 617 millimetres (24.3 in).

References

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