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Ustatochoerus major

Mammalia - Merycoidodontidae

Taxonomy
Merychyus major was named by Leidy (1858). Its type specimen is NM 439, a maxilla (Partial right maxilla with P3-M3), and it is a 3D body fossil. Its type locality is Niobrara River (coll. Hayden 1857), which is in a Barstovian/Clarendonian terrestrial horizon in the Loup Fork Formation of Nebraska.

It was recombined as Metoreodon major by Matthew (1924) and Thorpe (1937); it was recombined as Ustatochoerus major by Schultz and Falkenbach (1941), Schultz and Falkenbach (1947), Stevens and Stevens (1989), Voorhies (1990), Stevens and Stevens (2007) and Stevens et al. (2023).

Synonyms
Synonymy list
YearName and author
1858Merychyus major Leidy p. 26
1859Merychyus major major Leidy
1873Merychyus major Leidy p. 201
1884Merychyus major Cope p. 545
1902Merychyus major Hay p. 669
1909Merychyus (Metoreodon) profectus Matthew and Cook p. 394 fig. 15
1912Metoreodon relictus profectus Cook p. 45
1917Metoreodon profectus Barbour and Cook p. 165
1924Ticholeptus profectus Loomis
1924Metoreodon major Matthew
1937Metoreodon major Thorpe p. 205 figs. PI. XXXVII, figs. 12-13
1937Metoreodon profectus Thorpe p. 209 figs. Figs. 152-153; PI. XXX; PI. XXXI, fig. 1
1941Ustatochoerus major Schultz and Falkenbach p. 16
1941Ustatochoerus major texanus Schultz and Falkenbach p. 22
1941Ustatochoerus profectus Schultz and Falkenbach p. 36
1941Ustatochoerus profectus espanolensis Schultz and Falkenbach p. 43
1941Ustatochoerus profectus studeri Schultz and Falkenbach p. 45
1941Ustatochoerus skinneri Schultz and Falkenbach p. 47
1941Ustatochoerus skinneri santacruzensis Schultz and Falkenbach p. 49
1942Metoreodon profectus Gregory p. 328
1947Ustatochoerus major Schultz and Falkenbach
1947Ustatochoerus profectus Schultz and Falkenbach
1949Ustatochoerus profectus Schultz and Falkenbach p. 81
1968Ustatochoerus profectus nevadaensis Schultz and Falkenbach p. 372 figs. Figure 45
1988Merychyus major Kelly and Lander
1989Ustatochoerus major Stevens and Stevens
1989Ustatochoerus profectus Stevens and Stevens
1990Ustatochoerus major Voorhies
1998Merychyus major Lander
2007Ustatochoerus major Stevens and Stevens p. 166
2009Merychyus major Morgan et al.
2009Merychyus major major Morgan et al.
2023Ustatochoerus major Stevens et al. p. 119 figs. Figures 100-102; Appendix 12B; Table A40

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RankNameAuthor
kingdomAnimalia()
Bilateria
EubilateriaAx 1987
Deuterostomia
phylumChordataHaeckel 1874
subphylumVertebrata
superclassGnathostomata
Osteichthyes()
subclassSarcopterygii()
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda
Reptiliomorpha
Anthracosauria
subclassAmphibiosauriaKuhn 1967
Cotylosauria()
Amniota
subclassSynapsida
Therapsida()
infraorderCynodontia()
Mammaliamorpha
RankNameAuthor
Mammaliaformes
classMammalia
Theriamorpha(Rowe 1993)
Theriiformes()
Trechnotheria
Cladotheria
Zatheria
subclassTribosphenida()
subclassTheria
Eutheria()
Placentalia
Boreoeutheria
Laurasiatheria
Scrotifera
Euungulata
Artiodactylamorpha
Artiodactyla()
familyMerycoidodontidae
subfamilyUstatochoerinae
genusUstatochoerus
speciesmajor()

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.

Ustatochoerus major Leidy 1858
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Invalid names: Merychyus (Metoreodon) profectus Matthew and Cook 1909 [synonym], Merychyus major major Leidy 1859 [invalid subgroup], Ustatochoerus major texanus Schultz and Falkenbach 1941 [invalid subgroup], Ustatochoerus profectus espanolensis Schultz and Falkenbach 1941 [invalid subgroup], Ustatochoerus profectus nevadaensis Schultz and Falkenbach 1968 [invalid subgroup], Ustatochoerus profectus studeri Schultz and Falkenbach 1941 [invalid subgroup], Ustatochoerus skinneri Schultz and Falkenbach 1941 [synonym], Ustatochoerus skinneri santacruzensis Schultz and Falkenbach 1941 [invalid subgroup]
Diagnosis
ReferenceDiagnosis
C. B. Schultz and C. H. Falkenbach 1941SKULL.-Larger than that of U. profectus; elongated posterior to orbits; malar moderately deep; nasals short and retracted considerably more than those of U. profectus; anterior tip of nasals retracted to region above P 3 ; postglenoid process very large in comparison with that of U. profectus.
MANDIBLE.-Typical of genus; larger and more robust than in U. profectus; smaller and lighter than in U. californicus espanolensis.
DENTITION.-Well-developed cusps in superior and inferior premolars, more so than in U. medius; 'tendency for presence of cingula on superior molars; m- ferior premolars crowded and grooved on internal side.
LIMBS.-Longer and heavier than in examples of U. profectus.
C. B. Schultz and C. H. Falkenbach 1941 (Ustatochoerus profectus)SKULL.-Smaller than that of U. major and larger than that of U. medius; fan-shaped occipital region not as wide as in U. major; brain case slightly more inflated than in U. major; nasals shorter than in U. medius and decidedly longer than in U. major, and with less retraction than in the latter species; anterior tip of nasals retracted to region above P 2 ; paroccipital process long and tapered; postglenoid process not as heavy as in U. major.
MANDIBLE.-Typical of the genus, intermediate in size between those of U. medius and U. major.
DENTITION.-Superior and inferior series intermediate in length between those of U. medius and U. major.
LIMBs.-Shorter and lighter than in U. major; longer and heavier than in U. medius.
C. B. Schultz and C. H. Falkenbach 1941 (Ustatochoerus skinneri)SKULL.-Differs from U. major, the nearest form, in somewhat smaller size; occipital flare not as wide; nasals much longer and less retracted (an- terior tip of nasals above region of P2); palate not extended as far posteriorly.
MANDIBLE.-Not quite as long as that of U. major.
DENTITION.-Superior and inferior series of approximately same length as examples of U. major; inferior canine smaller and Pr lighter than in U. major; P4 usually lacks deep internal groove found in U. major.
LIMBs.-Heavier and shorter than those of U. major; nearly same length as those of U. profectus.
M. S. Stevens et al. 2023Large Ustatochoerus (P2-M3 length = 110-125 mm; M1-3 length = 70-85 mm; p2-m3 length = 115-145 mm; m1-3 length = 77-100 mm), larger than U. medius but smaller than U. californicus, with much more shortened and retracted nasals than U. medius, reaching above the P3; large postglenoid process compared to U. medius.