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Sifrhippus index

Osteichthyes - Perissodactyla - Equidae

Taxonomy
Orotherium index was named by Cope (1873). Its type specimen is AMNH 4680, a mandible, and it is a 3D body fossil.

It was synonymized subjectively with Orotherium uintanum by Cope (1875); it was recombined as Hyracotherium index by Cope (1877), Cope (1884), Wortman (1896), Matthew (1899), Gazin (1952), Gingerich (1989), Gingerich (1991), MacFadden (1998); it was recombined as Eohippus index by King (1878), Hay (1902), Granger (1908), Hay (1930), Stirton (1940); it was synonymized subjectively with Pliolophus uintanus by Cope (1886); it was synonymized subjectively with Hyracotherium angustidens by Lydekker (1886), Pavlow (1888), Kitts (1957); it was synonymized subjectively with Hyracotherium vasacciense vasacciense by Kitts (1956); it was synonymized subjectively with Hyracotherium vasacciense by Gazin (1962); it was recombined as Minippus index by Froehlich (2002); it was recombined as Sifrhippus index by Rej and Lucas (2016).

Entered
by J. Alroy on 2003-01-23; modified by M. Carrano on 2015-07-26

Synonyms
Synonymy list
YearName and author
1873Orotherium index Cope p. 4
1877Hyracotherium index Cope
1877Orotherium loevii Cope
1878Eohippus index King
1884Hyracotherium index Cope
1884Pliolophus loevii Cope
1896Hyracotherium index Wortman p. 99 figs. 9 and 10
1899Hyracotherium index Matthew
1902Eohippus index Hay p. 609
1908Eohippus index Granger
1930Eohippus index Hay
1940Eohippus index Stirton
1952Hyracotherium index Gazin
1989Hyracotherium index Gingerich
1989Hyracotherium sandrae Gingerich
1989Hyracotherium sulcatus Gingerich
1991Hyracotherium index Gingerich
1998Hyracotherium index MacFadden p. 542
1998Hyracotherium sandrae MacFadden p. 542
2002Sifrhippus sandrae Froehlich p. 159
2002Minippus index Froehlich pp. 162-163
2002Minippus jicarillai Froehlich pp. 164-165
2012Hyracotherium sandrae Rose et al.
2012Sifrhippus sandrae Secord et al. p. 962
2016Sifrhippus index Rej and Lucas p. 224 figs. 1, 2

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RankNameAuthor
kingdomAnimalia()
—Bilateria
—EubilateriaAx 1987
—Deuterostomia
phylumChordataHaeckel 1874
subphylumVertebrata
superclassGnathostomata
classOsteichthyes
subclassSarcopterygii()
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
—Tetrapoda
—Reptiliomorpha
—Anthracosauria
subclassAmphibiosauriaKuhn 1967
—Cotylosauria()
—Amniota
subclassSynapsida
—Therapsida()
infraorderCynodontia()
RankNameAuthor
—Mammaliamorpha
—Mammaliaformes
classMammalia
—Cladotheria
—Zatheria
subclassTribosphenida()
subclassTheria
—Eutheria()
—Placentalia
—Boreoeutheria
—Laurasiatheria
—Scrotifera
—Euungulata
—Panperissodactyla
superorderPerissodactylamorpha
orderPerissodactyla()
superfamilyEquoidea
familyEquidae
genusSifrhippus
speciesindex()

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

†Sifrhippus index Cope 1873
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Invalid names: Hyracotherium sulcatus Gingerich 1989 [synonym], Minippus jicarillai Froehlich 2002 [synonym], Orotherium loevii Cope 1877 [synonym], Sifrhippus sandrae Gingerich 1989 [synonym]
Diagnosis
ReferenceDiagnosis
D. J. Froehlich 2002 (Sifrhippus sandrae)Small early Eocene equid with a distinct bowl on the anterior part of the pre-ultimate lower molars formed by a strong paralophid connected to a strong premetacristid. The bowl-shaped paralophid is a unique apomorphy of this taxon. Three other characters were identified in this analysis as autapomorphies of this OTU: upper molar metaconule weak and stepped on metaloph (Character 49, 0 to 1), and long paralophid complex (Character 86, 0 to 1). This taxon is identified in the analysis as the basal equid and thus it shares all of these synapomorphies: P3 talonid forming a weak bowl (Character 73, 2 to 1), P4 entoconid small (Character 75, 2 to 1), lower molar hypolophid deeply notched (Character 91, 1 to 0), and predominately type I (Character 93, 3 to 1), ilium extended and wedge shaped, with concave crista ilica and complex tuber coxae (Character 111, 0 to 1), trochanter major of femur high (Character 116, 0 to 1), and astragalar trochlea slightly inclined (Character 121, 0 to 1). The taxon lacks the synapomorphies of the next more inclusive equid clade: lower molar postcristid buccal (Character 97, 1 to 0) and pre-M3 hypoconulid strong (Character 98, 1 to 0).
D. J. Froehlich 2002Small equids with a lower preultimate molar hypoconulid closely appressed against hypolophid (Character 95, 0 to 1), a buccal molar postcristid (Character 97, 1 to 0) and a strong pre-M3 hypoconulid (Character 98, 1 to 0). The group lacks the characters of the next more-derived equid clade, P4 posterior ridge moderate (Character 76, 0 to 1), lower premolar paralophid complex very short (Character 79, 1 to 0), and a rounded lower molar paracristid bend (Character 88, 1 to 0).
D. J. Froehlich 2002 (Minippus jicarillai)This taxon possesses no unique or unambiguous autapomorphies and is only diagnosed by the presence of the synapomorphies of the clade that contains the taxon and the lack of characters found in more-derived clades. The San Jose small OTU is the most basal representative of the Minippus clade and is diagnosed by the presence of lower preultimate molar hypoconulid closely appressed against hypolophid (Character 95, 0 to 1), but lacks the characters of the more-derived small taxa, lower molar metaconid twinned and second cusp equal in size (Character 83, 1 to 2), large lower molar metaconid separation (Character 84, 0 to 1), and M3 heel crenulated (Character 103, 0 to 1).
Measurements
No measurements are available
Composition: phosphaticsubp
Environment: terrestrialsubc
Locomotion: actively mobilec
Life habit: ground dwellingf
Diet: browserf
Reproduction: viviparoussubc
Created: 2005-06-08 10:11:09
Modified: 2005-08-31 16:55:50
Source: f = family, subc = subclass, c = class, subp = subphylum
References: Carroll 1988, Nowak 1991, Lillegraven 1979, Hendy et al. 2009, Ji et al. 2002

Age range: Wasatchian or 56.00000 to 51.10000 Ma

Collections (42 total)


Time interval Ma Country or state Original ID and collection number
Wasatchian56.0 - 51.1USA (New Mexico) Hyracotherium angustidens (15598 15607 15611)
Wasatchian56.0 - 51.1USA (Wyoming) Eohippus index (15483) Hyracotherium angustidens (15879) Hyracotherium index (15454 15551 15553 15554 15555 15556 15557 15937 15964 16056) Hyracotherium sandrae (15759 15760 15761 15771 15780) Hyracotherium vasacciense (15661 15662)
Wasatchian56.0 - 51.1USA (Texas) Hyracotherium angustidens (15838)
Early/Lower Eocene56.0 - 48.07USA (Wyoming) Hyracotherium sandrae (15591 154251 154253 154254 154255 154257 154258 154259 154263 154268 154269 154270 154271 154272 154274 154280 154281 154282)
Ypresian56.0 - 48.07Belgium (Hainaut) Sifrhippus sandrae (87947)