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Mesoreodon chelonyx

Mammalia - Ungulata - Merycoidodontidae

Mesoreodon chelonyx was named by Scott (1893) [genotype].

It was synonymized subjectively with Eporeodon major by Lander (1998).

Synonymy list
YearName and author
1893Mesoreodon chelonyx Scott p. 661
1893Mesoreodon intermedius Scott p. 661
1906Mesoreodon chelonyx Douglass p. 566
1907Eucrotaphus montanus Douglass p. 100 figs. Pl. 23
1907Mesoreodon latidens Douglass p. 101 figs. Pl. 25
1924Merycoides latidens Loomis
1924Mesoreodon laticeps Loomis
1924Eporeodon montanus Thorpe
1934Merycoides latidens Schlaikjer
1937Eporeodon montanus Thorpe p. 80 figs. Fig. 40 ; PL IX, figs. 1-3
1937Mesoreodon chelonyx Thorpe p. 98 figs. Fig. 65 PL IX, fig. 4; PI. XI, figs. 1-2
1937Mesoreodon intermedius Thorpe p. 102 figs. PI. XI, fig. 3
1937Merycoides latidens Thorpe p. 173 figs. Fig. 125; PI. XXVI
1940Mesoreodon danai Koerner
1940Mesoreodon wheeleri Koerner
1940Eporeodon montanus Scott p. 686
1949Mesoreodon chelonyx Schultz and Falkenbach p. 140 figs. 15, 16, 18, 19, 26
1954Desmatochoerus (Paradesmatochoerus) sanfordi Schultz and Falkenbach p. 197 figs. 8 - 11
1954Subdesmatochoerus montanus Schultz and Falkenbach p. 220 figs. 19 - 21
1968Eporeodon meagherensis Schultz and Falkenbach
1968Paramerycoidodon (Gregoryochoerus) meagherensis Schultz and Falkenbach
1996Mesoreodon chelonyx Stevens and Stevens
1998Eporeodon latidens Lander
2007Mesoreodon chelonyx Stevens and Stevens p. 160

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phylumChordataHaeckel 1847
subclassDipnotetrapodomorpha(Nelson 2006)
orderUngulata(Linnaeus 1766)

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.

W. B. Scott 1893Metapodials rather short and stout, ungual phalanges trowel-shaped and pointed.
W. B. Scott 1893 (Mesoreodon intermedius)Metapodials slender and elongate, and ungual phalanges like those of Merychyus.
C. B. Schultz and C. H. Falkenbach 1949SKULL: Medium size, with average examples equal to those of M. cheeki; sagittal crest prominent, moderately high; nasals without noticeable anterior retraction; posterior border of zygomatic arch similar to that of M. ckeeki but not extending posteriorly so far as in M. megalodonor M. megalodon sweeti; infraorbital foramen above P4; lacrimal fossa larger and deeper than in examples of M. cheeki; occipital condyles moderately large (considerable individual variation) ; paroccipital process not so wide at base as that in examples of M. cheeki, but with same angular position to the bulla as in that species; bulla inflated, somewhat oblong anteroposteriorly; postglenoid process heavy and wider laterally than anteroposteriorly.
MANDIBLE:Similar in size and shape to examples of M. ckeeki.
DENTITION: Similar to that of M. cheeki; tendency for slight diastema between P1 and Pl (not a constant character).
LIMBS: Moderately short; shorter and lighter than those in Promerycochoerus;equal to examples of M. cheeki in size and construction.
C. B. Schultz and C. H. Falkenbach 1954 (Desmatochoerus (Paradesmatochoerus) sanfordi)SKULL: Small size (smallest known of subgenus); no facial vacuity; anterior nasal-maxilla contact above the posterior portion of P1; infraorbital foramen above P3; · post-glenoid process comparably robust, higher and with less steeply sloping external border than in examples of D. (P.) wyomingensis. (Occipital region, bulla, zygomatic arch, and nasals unknown.)
MANDIBLE:Similar to examples of D. (P.) wyomingensis except for smaller size; post-symphysis below anterior portion of Pa.
DENTITION: Smallest known series of subgenus.
LIMBS: Long and slender; shortest examples of subgenus.
C. B. Schultz and C. H. Falkenbach 1954 (Subdesmatochoerus montanus)SKULL: Largest known form of genus; smaller than examples of Desmatochoerus and Pseudodesmatochoerus, larger than those of Prodesmatochoerus; sagittal crest light, high, and arched (more so than in examples of S. shannonensis), posterior portion slightly de- pressed; exoccipital vacuities larger than in S. socialis; nasals moderately light; zygomatic arch with more abrupt posterior rise than examples of S. shannonensis, more like those in S. socialis; malar deeper below orbit than in S. shannonensis; infraorbital foramen above P4 ; lacrimal fossa moderately large, very deep; slight depression posterior to infraorbital foramen; paroccipital process mod- erately light at base, with moderately down ward tapering, long axis of base paralleling longitudinal axis of skull; paroccipital process on external side of posterior portion of bulla (not directly posterior to bulla as in other examples of genus); bulla inflated, compressed laterally (similar, but larger than in examples of S. socialis dakotensis); post-glenoid process robust, wider than that in last-mentioned subspecies; posterior palate projecting farther posteriorly than in other forms of genus (palatal area partially restored in holotype).
MANDIBLE: More robust and deeper than in examples of S. shannonensis (more like examples of Desmatochoerus from the Gering) ; inferior border of ramus arched, somewhat like those of Brachycrus but shallower anteriorly; ascending ramus high, wide anteroposteriorly; condyle large and moderately robust.
DENTITION: Series more robust and of greater length than in examples of S. shannonensis; premolars crowded; p1-p3 and Pr P3 each set at angle to alveolar border; posterior external style of M3 more prominent than in other species of genus; P2 and P3 with anterior intermediate crest (P 1 may have crest, but not present on well-worn P1 of holotype).