Name: Hippidion
(Little horse).
Phonetic: Hip-pi-de-on.
Named By: Richard Owen - 1869.
Classification: Chordata, Mammalia,
Perissodactyla, Equidae.
Species: H. principale, H. saldiasi.
Diet: Herbivore.
Size: 1.4 meters high at the shoulders.
Known locations: Across South America.
Time period: Gelasian of the Pliestocene through to
early Holocene.
Fossil representation: Multiple specimens.
Hippidion
is one of the first known horses to actually enter South America, but
interestingly while it has been regarded as being directly descended
from primitive forms such as Pliohippus,
more modern analysis
actually draws a link to the Equidae, the group that includes modern
horses.
One
thing that makes Hippidion stand out from its North
American relatives
is the delicately domed nasal bone which likely allowed for an enlarged
nasal area. This has been suggested as allowing for an increased
sense of smell, although this would be a very curious adaptation for
a herbivore to make, especially for a grazing animal. It is more
likely that this enlarged nasal system was a climatic adaptation since
Hippidion would have been living in ecosystems where
the air was both
cold and dry. By passing the air through a set of enlarged and
possibly more complex air passages before reaching the lungs,
Hippidion could beat the cooling effects of the
chill air as well as
significantly reduce the amount of moisture lost through respiration.
With the lungs protected from drying out, Hippidion
would then avoid
having to deal with the ailments associated with long term exposure to
dry air.
Hippidion
is estimated to have died out at some point around the last ten
thousand years, a time that saw much of the other South American
megafauna disappear. This disappearance coincides with the arrival of
the first people in South America and hunting may have been a
significant factor in the decline of the South American megafauna at
this time, although perhaps not the single root cause of this mass
extinction. The next wave of horses to colonise South America would
not happen till the sixteenth century when they were brought over by
European explorers.
Further reading
- Contribuci�n al conocimiento de los mam�feros f�siles de la Rep�blica
Argentina [Contribution to the knowledge of the fossil mammals of the
Argentine Republic]. - Actas de la Academia Nacional de Ciencias de la
Rep�blica Argentina en C�rdoba 6:xxxii-1027. - F. Ameghino - 1889.
- Algo mas sobre Hippidium (Plagiohippus)
chapalmalensis (Amegh.)
Kragl. - Ameghiniana 2(3):39-45. E. F. de Alvarez - 1961.
-Evolution, systematics, and phylogeography of Pleistocene horses in
the New World: a molecular perspective. - PLOS Biology. 3 (8): e241. -
Jaco Weinstock, Eske Willerslev, Andrei Sher, Wenfei Tong, Simon Y.W
Ho, Dan Rubenstein, John Storer, James Burns, Larry Martin, Claudio
Bravi, Alfredo Prieto, Duane Froese, Eric Scott, Lai Xulong &
Alan Cooper - 2005.
- Ancient DNA Clarifies the Evolutionary History of American Late
Pleistocene Equids. - Journal of Molecular Evolution. 66 (5): 533–538.
- Ludovic Orlando, Dean Male, Maria Teresa Alberdi, Jose Luis Prado,
Alfredo Prieto, Alan Cooper & Catherine H�nni - 2008.
- Hippidion saldiasi Roth, 1899 (Equidae,
Perissodactyla), at the
Piedra Museo Site (Santa Cruz, Argentina): Its Implication for the
Regional Economy and Environmental Reconstruction. - Journal of
Archaeological Science. 28 (4): 411–419. - Mar�a T. Alberdia, Laura
Miottib & Jos� L.Pradoc - 2001.
- Mitochondrial genomes reveal the extinct Hippidion
as an outgroup to
all living equids. - Biology Letters. 11 (3): 20141058. - Clio Der
Sarkissian, Julia T. Vilstrup, Mikkel Schubert, Andaine Seguin-Orlando,
David Eme, Jacobo Weinstock, Maria Teresa Alberdi, Fabiana Martin,
Patricio M. Lopez, Jose L. Prado, Alfredo Prieto, Christophe J. Douady,
Tom W. Stafford, Eske Willerslev, & Ludovic Orlando - 2015.
- Assessing the Causes Behind the Late Quaternary Extinction of Horses
in South America Using Species Distribution Models. - Frontiers in
Ecology and Evolution. 7: 226. - Natalia A. Villavicencio, Derek
Corcoran & Pablo A. Marquet - 2019.