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Ustatochoerus medius

Mammalia - Merycoidodontidae

Taxonomy
Merychyus medius was named by Leidy (1858). Its type specimen is NM 118, a mandible (Partial left ramus with m1-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 medius by Thorpe (1937); it was recombined as Ustatochoerus medius by Schultz and Falkenbach (1941), Schultz and Falkenbach (1947), Galbreath (1953), Cassiliano (1980), Stevens and Stevens (1989), Voorhies (1990), Stevens and Stevens (2007), May (2019) and Stevens et al. (2023).

Synonyms
Synonymy list
YearName and author
1858Merychyus medius Leidy p. 26
1873Merychyus medius Leidy p. 201
1884Merychyus medius Cope p. 545
1890Merycochoerus coenopus Scott
1890Merycochoerus cenopus Scott and Osborn p. 73
1901Merycochoerus compressidens Douglass p. 79 fig. 4
1902Merycochoerus coenopus Hay p. 668
1902Merychyus medius Hay p. 669
1929Merychyus medius novomexicanus Frick p. 107
1937Merycochoerus coenopus Thorpe p. 153 figs. PI. XXXI, figs. 3-4
1937Metoreodon compressidens Thorpe p. 204 figs. Fig. 148
1937Metoreodon medius Thorpe p. 206 figs. PI. XXXVII, figs. 14-16
1937Merychyus novomexicanus Thorpe p. 207 figs. Figs. 149-151; PI. XXXI, fig. 2
1941Ustatochoerus compressidens Schultz and Falkenbach p. 15
1941Ustatochoerus medius Schultz and Falkenbach p. 23
1941Ustatochoerus medius novomexicanus Schultz and Falkenbach p. 33
1947Ustatochoerus medius Schultz and Falkenbach
1953Ustatochoerus medius Galbreath
1980Ustatochoerus medius Cassiliano
1988Merychyus medius Kelly and Lander
1989Merychyus medius Lander and Kelly
1989Ustatochoerus compressidens Stevens and Stevens
1989Ustatochoerus medius Stevens and Stevens
1990Ustatochoerus medius Voorhies
1998Merychyus medius Lander
1998Merychyus novomexicanus Lander
2007Ustatochoerus medius Stevens and Stevens p. 166
2009Merychyus medius Morgan et al. p. 95
2019Ustatochoerus medius May
2023Ustatochoerus medius Stevens et al. p. 119 figs. Figures 96A, 97C, 99; Appendix 12A; Table A39

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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
speciesmedius()

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 medius Leidy 1858
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Ustatochoerus medius mohavensis Schultz and Falkenbach 1941
Invalid names: Merychyus medius novomexicanus Frick 1929 [invalid subgroup], Merycochoerus coenopus Scott 1890 [synonym], Merycochoerus compressidens Douglass 1901 [synonym]
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Diagnosis
ReferenceDiagnosis
C. B. Schultz and C. H. Falkenbach 1941
SKULL.-Smaller than that of U. profectus but larger than that of U.? schrammi; nasals longest of genus (in proportion to size of skull); anterior tip of nasals retracted to region above PLP 2•
MANDIBLE.-Typical of genus; similar to that of U. profectus except for smaller size.
DENTITION.-Cusps on superior and inferior premolars not as well developed as in U. major or U. profectus.
LIMBs.-Smaller than those of U. profectus.
C. B. Schultz and C. H. Falkenbach 1941 (Ustatochoerus compressidens)SKULL.-Unknown.
MANDIBLE.-Similar to that of U. profectus.
DENTITION.-Superior series unknown; /c heavy; p1-p4 crowded and overlapping.
LIMBS.-Unknown.
M. S. Stevens et al. 2023Medium-sized Ustatochoerus (P2-M3 length = 70-110 mm; M1-3 length = 52-70 mm; p2-m3 length = 100-115 mm; m1-3 length = 52-77 mm) with slightly longer nasals; tip of nasals retracted to the level of P1-P2. The broad, ovoid skull has a saddle-like depression between the frontals and the sagittal crest, relatively short nasals, relatively large facial vacuities, deep malars with delicate zygomatic arches, arched frontal region, fan-shaped lambdoid crest in the occiput, and relatively high-crowned cheek teeth with molarized premolars that are crowded together and reduced in size compared to the molars.
Measurements
No measurements are available
Composition: phosphaticsubp
Environment: terrestrialo
Locomotion: actively mobilec
Life habit: ground dwellingf
Diet: herbivoref
Reproduction: viviparoussubc
Created: 2005-08-31 14:37:21
Modified: 2005-08-31 16:37:21
Source: f = family, o = order, subc = subclass, c = class, subp = subphylum
References: Hendy et al. 2009, Lillegraven 1979, Nowak 1999, Lander 1998, Carroll 1988

Age range: base of the Barstovian to the top of the Clarendonian or 15.97000 to 10.30000 Ma

Collections (62 total)


Time interval Ma Country or state Original ID and collection number
Miocene23.03 - 5.333USA (Nebraska) Ustatochoerus medius (18049 18264 18311 18319 18356 18469)
Miocene23.03 - 5.333USA (South Dakota) Ustatochoerus medius (18191)
Miocene23.03 - 5.333USA (Kansas) Ustatochoerus medius, Ustatochoerus profectus (18122)
Miocene23.03 - 5.333USA (Texas) Ustatochoerus profectus (18103)
Miocene23.03 - 5.333USA (New Mexico) Ustatochoerus medius (19518)
Barstovian15.97 - 13.6USA (Colorado) Ustatochoerus medius (18203 18220)
Barstovian15.97 - 13.6USA (New Mexico) Ustatochoerus medius (19287 19535)
Barstovian15.97 - 13.6USA (Nebraska) Ustatochoerus medius (18031 18101 18124 18125 18141 18155 18164 18192 18216 18275 18281 18284 18442 18443) Ustatochoerus medius, Ustatochoerus profectus (18123) Ustatochoerus profectus (18119 18464)
Barstovian - Clarendonian15.97 - 10.3USA (Nebraska) Merychyus medius (190543) Ustatochoerus medius (18077 18270 18280 18290) Ustatochoerus medius, Ustatochoerus profectus (18070)
Barstovian - Clarendonian15.97 - 10.3USA (Colorado) Ustatochoerus medius (18445)
Clarendonian13.6 - 10.3USA (South Dakota) Metoreodon profectus (18063) Ustatochoerus profectus (18200) Ustatochoerus skinneri (18268)
Clarendonian13.6 - 10.3USA (Texas) Oreodontidae indet. (18645) Ustatochoerus medius, Metoreodon sp. (18623) Ustatochoerus profectus (18096 18104 18244 18355)
Clarendonian13.6 - 10.3USA (Nebraska) Ustatochoerus medius (18260) Ustatochoerus profectus (18042 18060 18204 18251 18301 18362 18447) Ustatochoerus skinneri (18092 18315 18324)
Clarendonian13.6 - 10.3USA (Oklahoma) Ustatochoerus profectus (18045)
Late/Upper Clarendonian13.6 - 10.3USA (Nebraska) Ustatochoerus medius (18207)
Clarendonian - Hemphillian13.6 - 4.9USA (Wyoming) Ustatochoerus medius (18424)
Clarendonian - Hemphillian13.6 - 4.9USA (Nebraska) Ustatochoerus profectus (18134)