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