''Rhynchippus'' ("beaked horse") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of notoungulate mammals from the

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

(

Deseadan The Deseadan () age is a period of geologic time (29.0–21.0 Ma) within the Oligocene epoch of the Paleogene to the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification of South America. It follows the Tingu ...

in the SALMA classification) of South America. The genus was first described by

Florentino Ameghino Florentino Ameghino (born Giovanni Battista Fiorino Giuseppe Ameghino; September 19, 1853 – August 6, 1911) was an Argentine naturalist, paleontologist, anthropologist and zoologist, whose fossil discoveries on the Argentine Pampas, especial ...

in 1897 and the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''R. equinus'', with

lectotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to anchor or centralizes ...

MACN A 52–31. Fossils of ''Rhynchippus'' have been found in the Agua de la Piedra and

Sarmiento Formation The Sarmiento Formation (Spanish language, Spanish: ''Formación Sarmiento''), in older literature described as the Casamayor Formation, is a geological formation in Chubut Province, Argentina, in central Patagonia, which spans around 30 million y ...

s of

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

, the Salla and Petaca Formations of

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

, the Tremembé Formation of

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

,''Rhynchippus''
at

Fossilworks Fossilworks was 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 cr ...

.org and the Moquegua Formation of

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

Description

''Rhynchippus'' was about in length and weighed up to , with a deep body and three clawed toes on each foot.Patterson & Pires Costa, 2012, p.83 Although its

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

were extremely similar to those of

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...

s or rhinos, ''Rhynchippus'' was actually a relative of '' Toxodon'', having developed teeth suitable for

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to free range (roam around) and consume wild vegetations in order to feed conversion ratio, convert the otherwise indigestible (by human diges ...

through

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 comm ...

. Unlike its relatives, ''Rhynchippus'' had no large tusks; they were the same size and shape as the

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

s. Enamel on the

molars The molars or molar teeth are large, flat tooth, teeth at the back of the mouth. They are more developed in mammal, mammals. They are used primarily to comminution, grind food during mastication, chewing. The name ''molar'' derives from Latin, '' ...

allowed it to chew tough food.Palmer et al., 1999, p.252 The genus shows similarities with '' Mendozahippus'', '' Eurygenium'' and '' Pascualihippus''. In

2016 2016 was designated as: * International Year of Pulses by the sixty-eighth session of the United Nations General Assembly. * International Year of Global Understanding (IYGU) by the International Council for Science (ICSU), the Internationa ...

, a well-preserved specimen of ''R. equinus'' was described by Martínez et al. from the

in central

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

. The extraordinary preservation of the specimen allowed the researchers to appreciate the three connected spaces that constitute a heavily pneumatized middle ear; the epitympanic sinus, the tympanic cavity itself, and the ventral expansion of the tympanic cavity through the notably inflated bullae.

Paleoecology

Fossils of ''Rhynchippus'' have been found in various fossiliferous stratigraphic units in South America, all restricted to the

South American land mammal age The South American land mammal ages (SALMA) establish a geologic timescale for prehistoric South American fauna beginning 64.5 Ma during the Paleocene and continuing through to the Late Pleistocene (0.011 Ma). These periods are referred to as age ...

. Several specimens come from the

in the Golfo San Jorge Basin in central

, with other finds from the Petaca Formation of the Subandean Belt in Bolivia, the Salla Formation from the same country, the Moquegua Formation of the Moquegua Basin in southern

, the Agua de la Piedra Formation of the Neuquén Basin in Argentina, and the Tremembé Formation of the Taubaté Basin in eastern

. The Sarmiento and Salla Formations have provided a rich assemblage of many mammals and terror birds, as '' Physornis''. The faunal assemblage of ''Rhynchippus'' fossil locations also constitutes several

crocodilia Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchia ...

ns, snakes ('' Madtsoia''), helmeted bull frogs, a catfish; '' Taubateia paraiba'', and the

caiman A caiman ( (also spelled cayman) from Taíno language, Taíno ''kaiman'') is an alligatorid belonging to the subfamily Caimaninae, one of two primary lineages within the Alligatoridae family (biology), family, the other being alligators. ...

'' Caiman tremembensis''. The Tremembé Formation is known for the preservation of several insects.

Gallery

Notes and references

Notes

References

Bibliography

* * * {{Taxonbar, from=Q911486 Toxodonts Chattian life Oligocene mammals of South America Deseadan Paleogene Argentina Fossils of Argentina Golfo San Jorge Basin Paleogene Bolivia Fossils of Bolivia Paleogene Brazil Fossils of Brazil Paleogene Peru Fossils of Peru Fossil taxa described in 1897 Taxa named by Florentino Ameghino Prehistoric placental genera Sarmiento Formation