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Plesippus simplicidens
Taxonomy
Equus simplicidens was named by Cope (1892). Its type specimen is TMM 40282-6, a tooth (left M1), and it is a 3D body fossil.
It was recombined as Pliohippus simplicidens by Gidley (1901), Hay (1902), Gidley (1903), Trouessart (1905), Gidley (1907), Matthew (1909), Merriam (1916), Osborn (1918) and Schultz (1936); it was recombined as Hippotigris simplicidens by McGrew (1944), Meade (1945) and Quinn (1955); it was recombined as Equus (Plesippus) simplicidens by Howe (1970) and Forsten and Eisenmann (1995); it was recombined as Equus (Dolichohippus) simplicidens by Skinner (1972) and MacFadden (1998); it was considered a nomen dubium by Macdonald (1992); it was recombined as Plesippus simplicidens by Matthew (1924), Gidley (1930), Gazin (1936), Schultz (1936), Hibbard (1944), Strain (1966), Repenning et al. (1995) and Barrón-Ortiz et al. (2019).
It was recombined as Pliohippus simplicidens by Gidley (1901), Hay (1902), Gidley (1903), Trouessart (1905), Gidley (1907), Matthew (1909), Merriam (1916), Osborn (1918) and Schultz (1936); it was recombined as Hippotigris simplicidens by McGrew (1944), Meade (1945) and Quinn (1955); it was recombined as Equus (Plesippus) simplicidens by Howe (1970) and Forsten and Eisenmann (1995); it was recombined as Equus (Dolichohippus) simplicidens by Skinner (1972) and MacFadden (1998); it was considered a nomen dubium by Macdonald (1992); it was recombined as Plesippus simplicidens by Matthew (1924), Gidley (1930), Gazin (1936), Schultz (1936), Hibbard (1944), Strain (1966), Repenning et al. (1995) and Barrón-Ortiz et al. (2019).
Sister species lacking formal opinion data
Synonyms
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Synonymy list
Year | Name and author |
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1869 | Equus tau Owen p. 565 |
1870 | Equus tau Owen |
1892 | Equus simplicidens Cope p. 124 fig. 1 |
1893 | Equus simplicidens Cope p. 66 |
1901 | Equus tau Gidley p. 120 |
1901 | Pliohippus simplicidens Gidley p. 124 fig. 13 |
1902 | Pliohippus simplicidens Hay p. 618 |
1902 | Equus tau Hay p. 624 |
1903 | Pliohippus simplicidens Gidley |
1905 | Pliohippus simplicidens Trouessart |
1907 | Pliohippus simplicidens Gidley p. 911 |
1909 | Pliohippus simplicidens Matthew |
1913 | Equus littoralis Hay p. 575 |
1916 | Pliohippus simplicidens Merriam |
1918 | Pliohippus simplicidens Osborn p. 167 figs. Plates 24.5, 28.5. Text Fig. 134. |
1924 | Plesippus simplicidens Matthew |
1930 | Plesippus simplicidens Gidley |
1930 | Plesippus shoshonensis Gidley p. 301 figs. Plate 18 |
1930 | Equus achates Hay and Cook |
1935 | Equus tau Schultz and Howard p. 286 |
1936 | Plesippus simplicidens Gazin |
1936 | Plesippus simplicidens Schultz |
1936 | Pliohippus simplicidens Schultz |
1940 | Equus shoshonensis Stirton p. 195 |
1940 | Equus simplicidens Stirton p. 195 |
1942 | Plesippus shoshonensis Gazin |
1944 | Plesippus simplicidens Hibbard |
1944 | Hippotigris simplicidens McGrew p. 55 |
1945 | Hippotigris simplicidens Meade |
1949 | Equus simplicidens Hibbard and Riggs |
1951 | Equus simplicidens Hibbard |
1955 | Hippotigris shoshonensis Quinn p. 46 |
1955 | Hippotigris simplicidens Quinn p. 46 |
1957 | Onager littoralis Quinn p. 13 |
1958 | Asinus pons Quinn p. 605 figs. 1, 2 |
1966 | Equus pons Azzaroli |
1966 | Plesippus simplicidens Strain |
1970 | Equus (Plesippus) simplicidens Howe p. 959 |
1972 | Equus (Dolichohippus) simplicidens Skinner p. 118 |
1979 | Equus (Hemionus) tau Dalquest p. 242 |
1980 | Equus simplicidens Kurten and Anderson p. 285 |
1980 | Equus tau Kurten and Anderson p. 288 |
1989 | Equus simplicidens Winans |
1989 | Plesippus shoshonensis Winans p. 301 fig. 1 |
1990 | Equus simplicidens Schultz |
1995 | Equus (Plesippus) simplicidens Forsten and Eisenmann p. 88 |
1995 | Equus simplicidens Kelly p. 19 |
1995 | Plesippus shoshonensis Repenning et al. |
1995 | Plesippus simplicidens Repenning et al. |
1997 | Equus simplicidens Kelly |
1998 | Equus simplicidens Kelly |
1998 | Equus (Dolichohippus) simplicidens MacFadden p. 551 |
2019 | Plesippus simplicidens Barrón-Ortiz et al. p. 9 |
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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.
†Plesippus simplicidens Cope 1892
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Invalid names: Equus achates Hay and Cook 1930 [synonym], Equus pons Quinn 1958 [synonym], Equus shoshonensis Gidley 1930 [synonym], Equus tau Owen 1869 [synonym]
Diagnosis
Reference | Diagnosis | |
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H. F. Osborn 1918 | (1) about that of E. cahallus. (2) Internal column [protocone] is of moderate anteroposterior extent, its posterior border marking the anterior third of the posterior lake [post fossette]; (3) its long diameter is considerably less than half that of the crown; (4) extreme simplicity of the enamel borders of the lakes; (5) pli caballin, also a crochet fold in prefossette; (6) metastyle narrowed and not flattened; (7) parastyle more flattened. | |
J. W. Gidley 1930 (Plesippus shoshonensis) | Size about that of Equus niobrarensis or of a domestic horse of about fourteen or fifteen hands height; skull with shallow but well defined facial pits; muzzle and facial region long with orbit set well back; nasals relatively long and slender; basicranial region shorter and more bent downward than in Equus; cheek teeth long as in Equus, but in general more curved than is usual in the latter, and less curved than in Pliohippus; cement lakes in upper cheek teeth somewhat more open and with less elaborate enamel folding than is usual in Equus; proto- cones much more lengthened anteroposteriorly than in Pliohippus but less so than the average in Equus; lingual wall of protocone completely flattened, in some specimens definitely bent inward and presenting the longitudinal groove so com- monly found in Equus.
This species may be distinguished from P. simplicidens by the seemingly more distinct invagination of the facial pits; the more posterior position of the orbits; and from both P. simplicidens and P. proversus,by the generally more advanced or Equus-like development of the cheek teeth as indicated by the greater length- ening and greater curvature of the upper molars and by the generally more trans- versely flattened and grooved protocones. | |
J. H. Quinn 1957 (Onager littoralis) | Smallest of the Equini, teeth slightly larger than those of Nannippus phlegon. (From Hay, 1913a, p. 575) "Characterized by teeth of small size . . . enamel surrounding the lakes rather strongely folded. The crown somewhat more curved than in E. leidyi." | |
J. H. Quinn 1958 (Asinus pons) | Teeth slightly larger than in Asinus somaliensis Noak, protocones shorter with pronounced spur on anterior border as in A. mexicanus (Lance), more hypsodont than in A. mexicanus; metarsal equal in length to that of A. somaliensis, larger and stouter than in A. mexicanus; metacarpal longer than in A. somaliensis. | |
M. C. Winans 1989 (Plesippus shoshonensis) | Size about that of Equus niobrarensis or of a domestic horse of about fourteen or fifteen hands height; skull with shallow but well defined facial pits; muzzle and facial region long with orbit set well back; nasals relatively long and slender; basicranial region shorter and more bent downward than in Equus; cheek teeth long as in Equus, but in general more curved than is usual in the latter, and less curved than in Pliohippus; cement lakes in upper cheek teeth somewhat more open and with less elaborate enamel folding than is usual in Equus; proto- cones much more lengthened anteroposteriorly than in Pliohippus but less so than the average in Equus; lingual wall of protocone completely flattened, in some specimens definitely bent inward and presenting the longitudinal groove so com- monly found in Equus.
This species may be distinguished from P. simplicidens by the seemingly more distinct invagination of the facial pits; the more posterior position of the orbits; and from both P. simplicidens and P. proversus,by the generally more advanced or Equus-like development of the cheek teeth as indicated by the greater length- ening and greater curvature of the upper molars and by the generally more trans- versely flattened and grooved protocones. |