''Pachyrukhos'' is an extinct genus of hegetotheriid

notoungulate Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resemb ...

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 y ...

(

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 ag ...

Friasian The Friasian age is a period of geologic time (16.3–15.5 Ma) within the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification of South America. It follows the Santacrucian and precedes the Colloncuran age. ...

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 Sarmiento may refer to: Places Argentina *Sarmiento Department, San Juan, a subdivision of the San Juan Province *Sarmiento Department, Santiago del Estero, a subdivision of the Santiago del Estero Province *Sarmiento Department, Chubut, a subdivi ...

and

Santa Cruz Formation The Santa Cruz Formation is a geological formation in the Magallanes/Austral Basin in southern Patagonia in Argentina and in adjacent areas of Chile. It dates to the late Early Miocene epoch, and is contemporaneous with eponymous Santacrucian ...

s of Argentina and the

Río Frías Formation Río Frías Formation ( es, Formación Río Frías) is a Middle Miocene geologic formation made up sedimentary rock located in Aysén Region, western Patagonia. The formation crops out along the upper couse of Cisnes River ( es, Río Cisnes).Mar ...

of Chile.''Pachyrukhos''
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals ...

.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 speci ...

, 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, the ...

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 In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psycholog ...

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