''Periphragnis'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of isotemnid notoungulates that lived from the Middle

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

to the Early

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

in what is now

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

and

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

Description

This animal was of robust build, with powerful, probably

digitigrade In terrestrial vertebrates, digitigrade () locomotion is walking or running on the toes (from the Latin ''digitus'', 'finger', and ''gradior'', 'walk'). A digitigrade animal is one that stands or walks with its toes (metatarsals) touching the groun ...

legs ending in hooves. The forelegs, particularly robust, shared similarities with those of its relative ''

Thomashuxleya ''Thomashuxleya'' is an extinct genus of notoungulate mammal, named after famous 19th-century biologist Thomas Huxley. Description ''Thomashuxleya'' was about in length and weighted an estimated , with a heavy body and strong limbs.D. Patters ...

'', but had less flattened ungulate phalanges. ''Periphragnis'' was approximately one meter and a half long, around the size of a modern

boar The wild boar (''Sus scrofa''), also known as the wild swine, common wild pig, Eurasian wild pig, or simply wild pig, is a suid native to much of Eurasia and North Africa, and has been introduced to the Americas and Oceania. The species is no ...

. Its skull had a small neurocranium, and the dentition was complete and almost without any diastema. The canines were large-sized. ''Periphragnis'' had multiple similarities with ''Thomashuxleya'', but its teeth had a slightly higher crown, although still brachydont. The parastyle and paracon folds in the upper molars were less prominent, as well as less distinctly separated ; the folds of the parastyle, in the upper teeth of the jugal area, intersected with the labial metastyle of the previous teeth. The second lower premolar was more complex than in ''Thomashuxleya'', with a well-developed posterolingual sulcus ; the lower premolars were generally shorter and relatively wider, while the set of incisors was positioned more transversely.

Classification

The genus ''Periphragnis'' was first described in 1899 by Santiago Roth, based on fossils found around Lago Musters, in

, in terrains dated from the Middle Eocence. The type species is ''Periphragnis harmeri''. Other species of early notoungulates from the same geological horizon and the same area, such as ''Asmodeus armatus'', ''Tehuelia regia'' and ''Thomashuxleya rankei'', were later recognized as synonymous with ''Periphragnis harmeri''. Other species attributed to the genus are ''P. circunflexus'', from the Middle-Late Eocene of Argentina, ''P. exauctus'' and ''P. palmeri'', both from the Late Eocene of Argentina, and ''P. vicentei'', from the Early Oligocene of Tinguiririca,

. ''Periphragnis'' has historically been considered a rather derived member of the

Isotemnidae Isotemnidae is an extinct Family (biology), family of Notoungulata, notoungulate mammals known from the Paleocene (Las Flores Formation, Golfo San Jorge Basin, Las Flores Formation, Itaboraian) to Middle Miocene (Honda Group, Colombia, Honda Grou ...

, a group of archaic notoungulates with a massive build. For some of the characteristics of its limbs, ''Periphragnis'' has been compared to the

Homalodotheriidae Homalodotheriidae is an extinct family comprising four genera of notoungulate mammals known from the Late Eocene (Tinguirirican) through Late Miocene (Chasicoan) of Argentina and Chile in South America South America is a continent enti ...

, and some researchers thinks it was a basal form from this group. Recently, the status of Isotemnidae as a monophyletic group has been discussed, and ''Periphragnis'' is considered a basal toxodont along with ''Thomashuxleya''.

Palaeobiology

Like several other isotemnids, ''Periphragnis'' fed on roots and tubers he dug up with his powerful legs and minced with his strong front teeth. The characteristics of the molars and incisors indicate that this animal may have been a grazer.J. Bradham, J. J. Flynn, D. A. Croft and A. R. Wyss. 2015. New Notoungulates (Notostylopidae and Basal Toxodontians) from the Early Oligocene Tinguiririca Fauna of the Andean Main Range, Central Chile. American Museum Novitates 3841:1-24

Bibliography and References

* S. Roth. 1899. Aviso preliminar sobre mamíferos mesozóicos encontrados en Patagonia reliminary notice on Mesozoic mammals found in Patagonia Revista del Museo de La Plata 9:381-388 *F. Ameghino. 1901. Notices préliminaires sur des ongulés nouveaux des terrains crétacés de Patagonie reliminary notes on new ungulates from the Cretaceous terrains of Patagonia Boletin de la Academia Nacional de Ciencias de Córdoba 16:349-429 *F. Ameghino. 1902. Notices préliminaires sur des mammifères nouveaux des terrains Crétacé de Patagonie {preliminary notes on new mammals from the Cretaceous terrains of Patagonia]. Boletin de la Academia Nacional de Ciencias de Córdoba 17:5-70 {{Taxonbar, from=Q97371603 Toxodonts Eocene mammals of South America Oligocene mammals of South America Paleogene Argentina Fossils of Argentina Paleogene Chile Fossils of Chile Fossil taxa described in 1899 Prehistoric placental genera Golfo San Jorge Basin Sarmiento Formation