Rhopalodon is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of synapsid

Synapsid

Synapsids are a group of animals that includes mammals and everything more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having an opening low in the skull roof behind each eye, leaving a bony arch beneath each, accounting for their name...

 from the Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

 of Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

. It has been variously classified as a dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

, a dinocephalia

Dinocephalia

Dinocephalia are a clade of large early therapsids that flourished during the Middle Permian, but became extinct leaving no descendants.-Description:...

n, or another branch of Reptilia. Rhopalodon is notable for being among the first reptiles mentioned in Nature

Nature (journal)

Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...

. T.H. Huxley wrote of this reptile, among others, in the inaugural issue of the magazine, in November 1869. He gave the age of this animal and of the contemporary Deuterosaurus

Deuterosaurus

Deuterosaurus is a genus of the Therapsids, one of the "mammal-like” reptiles dominating land during the late Palaeozoic.-Anatomy:Skulls of Deuterosaurus are well-known from several finds. They were around 80 cm with a long snout and conical teeth. Like all anteosaurs, the skull possessed long,...

as Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

, but both are now known to have lived during the Middle Permian.

According to Tverdokhlebov et al. (2005), Rhopalodon was a medium-sized terrestrial dinocephalian herbivore that was characteristic of the early Tatarian Urzhumian biostratigraphic zone

Biostratigraphy

Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them. Usually the aim is correlation, demonstrating that a particular horizon in one geological section represents the same period...

(Bolshekinelskaya and Amanakskaya svitas).