Equus francisci

''Haringtonhippus'' is an extinct genus of stilt-legged equine from the Pleistocene of North America The genus is monospecific, consisting of the species ''H. francisci'', initially described in 1915 by Oliver Perry Hay as ''Equus francisci''. Prior to its formal description, it was sometimes referred to as the New World stilt-legged horse.

''Haringtonhippus'' fossils have only been discovered in North America. Specimens have been found from southern Mexico to southern South Dakota and in Alberta, Canada, at sites such as Gypsum Cave and Natural Trap Cave, as well as eastern Beringia in Yukon A later study found that ''Equus cedralensis'' from the Late Pleistocene of Mexico also belonged to this species. The earliest species of the lineage appeared in North America during the Late Pliocene to Early Pleistocene, around 2 to 3 Ma. It became extinct at the end of the Late Pleistocene.

Taxonomy

''Haringtonhippus'' is named after Charles Richard Harington. It was originally described as a new ''Equus'' species, ''E. francisci'', in 1915. Dalquest (1979) considered ''Equus tau'' , described from teeth in Mexico, a senior synonym of ''E. francisci'', while ''Equus quinni'' and ''E. arrelanoi'' were synonymized with ''E. francisci'' by Winans (1989). The species ''Equus achates'' Hay and Cook, 1930 (synonymized with ''E. tau'' by Dalquest 1979) was synonymized with ''E. francisci'' by Hulbert (1995), who also declared ''E. tau'' and ''E. littoralis'' ''nomina dubia''.Hulbert, R. C. 1995. Equus from Leisey Shell Pit 1A and other Irvingtonian localities from Florida. Bulletin of the Florida Museum of Natural History 37:553—602.

Phylogenetics

A 2017 paper placed ''Equus francisci'' outside ''Equus'' based on a phylogenetic analysis of DNA sequences, leading to erection of the new genus ''Haringtonhippus''. The genus is phylogenetically closer to '' Equus'' than to ''Hippidion''. It is estimated to have diverged from ''Equus'' around 4.1–5.7 million years ago, during the late Hemphillian or early Blancan.

A 2019 morphological study found ''H. francisci'' to be nested within ''Equus'' in a polytomy with '' E. conversidens'' and the plains zebra (''E. quagga''), supporting synonymization of ''Haringtonhippus'' with ''Equus''. The genetic study had not included '' E. stenonis'' and '' E. simplicidens'' (which were recovered by morphology as outgroups of ''Equus'', albeit closer to ''Equus'' than ''Hippidion'', reassigning them to ''Allohippus'' and ''Plesippus'', respectively) due to a lack of genetic data for these species, and so did not resolve their relationships to ''H. francisci''. To further explore this, a second morphological analysis was performed in which ''H. francisci'' was constrained to lie outside of crown ''Equus''. In this analysis, ''H. francisci'' was found to be a sister clade of either crown ''Equus'' or the clade comprising crown ''Equus'' + '' E. idahoensis'', but with trees 6 steps longer than the most parsimonious unconstrained analysis.

In addition to its phylogenetic position, the divergence times estimated from DNA sequences may suggest that ''Haringtonhippus'', and possibly even ''Hippidion'', should possibly be synonymised with ''Equus'' based on the divergence time criterion (i.e. that groups should be considered distinct genera only if they diverged long before the Miocene–Pliocene

HOME


Content is Copyleft
Website design, code, and AI is Copyrighted (c) 2014-2017 by Stephen Payne


Consider donating to Wikimedia



As an Amazon Associate I earn from qualifying purchases