''Sifrhippus'' is an extinct
genus of
equid
Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, asses, and zebras, and many other species known only from fossils. All extant species are in the genus '' Equus'', w ...
containing the species ''S. sandrae''. ''Sifrhippus'' is the oldest known equid, living during the early
Eocene. Its fossils were discovered in the
Bighorn Basin of
Wyoming.
Description
''Sifrhippus'' looked similar to modern horses, but were more slender and much smaller. Individuals likely weighed between ; the size variance, according to one theory, depended on the warmth of the climate.
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Taxonomy
''Sifrhippus sandrae'' is referred to in earlier literature as ''Hyracotherium sandrae'', but Froehlich, arguing that the traditional genus '' Hyracotherium'' was not monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
, reassigned many of its species to other genera. Froehlich gave ''H. sandrae'' the new generic
Generic or generics may refer to:
In business
* Generic term, a common name used for a range or class of similar things not protected by trademark
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name ''Sifrhippus'', derived from the Arabic '' صِفْر'' (''ṣifr''), "zero", and Greek '' ἵππος'' (''híppos''), "horse".
Since Froehlich's reorganization of ''Hyracotherium'' based on the morphological differences between fossil specimens, one further study has suggested that ''Sifrhippus sandrae'' and ''Minippus jicarillai'' are synonymous, and also that ''Minippus index'', although not seen by the authors of this study, is a synonym for the same taxon, which should then be named ''Sifrhippus index''. It has been argued that the differences in the fossils are more likely caused by individual variation in animals.
References
{{Taxonbar, from=Q291458
Eocene horses
Eocene odd-toed ungulates
Prehistoric placental genera
Ypresian life
Wasatchian
Paleogene mammals of North America
Fossil taxa described in 2002