''Pachyrukhos'' is an extinct genus of hegetotheriid notoungulate from the Early to

Middle Miocene The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma (million ...

(

Colhuehuapian The Colhuehuapian age is a period of geologic time (21.0–17.5 Ma) within the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification in South America. It follows the Deseadan and precedes the Santacrucian age. ...

Friasian The Friasian age is a period of geologic time (16.3–15.5 Ma) within the Early Miocene epoch of the Neogene The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the ...

in the SALMA classification) of

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 ...

. Fossils of this genus have been found in the Collón Curá, Sarmiento and Santa Cruz Formations of Argentina and the Río Frías Formation of Chile.''Pachyrukhos''
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was crea ...

.org

Description

It was about long and closely resembled a

rabbit Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit spec ...

, with a short tail and long hind feet. ''Pachyrukhos'' was probably also able to hop, and it had a rabbit-like

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, t ...

with teeth adapted for eating nuts and tough plants. The complexity of its hearing apparatus in the skull suggests that its

hearing Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditor ...

would have been very good, and that it probably had large ears. It also had large eyes, suggesting that it may have been nocturnal. These similarities are the result of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

, since, while quite unrelated to modern rabbits, ''Pachyrukhos'' filled the same

ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for ...

References

Typotheres Miocene mammals of South America Friasian Santacrucian Colhuehuapian Neogene Argentina Fossils of Argentina Neogene Chile Fossils of Chile Fossil taxa described in 1885 Taxa named by Florentino Ameghino Prehistoric placental genera Austral or Magallanes Basin Golfo San Jorge Basin Santa Cruz Formation Sarmiento Formation {{paleo-mammal-stub