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Vivaron

Vivaron
Temporal range: Late Triassic, 212 Ma
Vivaron.jpg
Right maxilla of the holotype
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Family: Rauisuchidae
Genus: Vivaron
Lessner, 2016
Type species
Vivaron haydeni
Lessner et al, 2016

Vivaron is a genus of rauisuchid known from the Late Triassic (middle Norian) Chinle Formation in New Mexico. It is the second rauisuchid known from the southwestern United States, and it highlights the wide biogeographic range similar rauisuchid taxa occupied during the Late Triassic across Pangaea, despite the varied faunal assemblages at different latitudes.

Vivaron was named in 2016 from material collected at the Hayden Quarry at Ghost Ranch, New Mexico in 2009. The locality is part of the Chinle Formation in the Petrified Forest Member, and dates to the middle Norian ~212 Ma, possibly representing one of the youngest known rauisuchids. Prior to its description, all Late Triassic rauisuchid material from Texas, Arizona and New Mexico had been referred to Postosuchus kirkpatricki. However, the rauisuchid remains from Hayden Quarry could be clearly distinguished from Postosuchus, and was erected as a new taxon Vivaron haydeni.

The generic epithet was named for Vivaron, a mythical 30 foot rattlesnake spirit that was said to live under Mesa Huerfano (Orphan Mesa) at Ghost Ranch, and the specific name in honour of John Hayden, a hiker who discovered the Hayden Quarry in 2002 where the material for Vivaron was collected.

Vivaron is known only from three jaw bones, associated skull fragments and referred hip bones. Comparisons with related taxa allow for an estimated length of 12 to 18 feet (~3.5 to ~5 metres), similar in size and appearance to other rauisuchids.

Vivaron can be distinguished from other rauisuchids by the presence of two prongs on the posterior portion of the maxilla where it articulates with the jugal. It is also unique among rauisuchids by possessing five aveoli in the premaxilla, similar to the state in early crocodylomorphs but in contrast with other rauisuchids, which only have four alveoli (however, a reconstruction of a Postosuchus skull (UCMP A269) figured in Long & Murry 1995 (Fig. 121) possibly shows a fifth alveolus in the left premaxilla). Vivaron was noted to share a number of characteristics with Teratosaurus, to which it is believed to be closely related to, particularly features of the maxilla and antorbital fossa. The referred hip elements also share similarities to the referred hips of Teratosaurus, potentially supporting their referral to each taxon, despite neither being directly associated with the holotype.


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