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Mammalia - Ungulata - Merycoidodontidae

Synonymy list
YearName and author
1848Merycoidodon Leidy
1851Oreodon Leidy p. 238
1851Cotylops Leidy p. 239
1884Oreodon Cope p. 505
1887Eucrotaphus (Oreodon) Scott and Osborn p. 155
1891Oreodon Cope p. 21
1902Merycoidodon Hay p. 665
1908Merycoidodon Lambe
1917Oreodon Barbour and Cook
1924Oreodon Sinclair
1937Merycoidodon Thorpe p. 45
1940Merycoidodon Scott p. 652 figs. Plates LXIX, LXX, LXXI, LXXIII
1949Promesoreodon Schultz and Falkenbach p. 152 figs. 21-25
1953Merycoidodon Galbreath
1954Subdesmatochoerus Schultz and Falkenbach p. 217 figs. 18 - 21
1954Prodesmatochoerus Schultz and Falkenbach p. 225 figs. 18, 22, 24 - 25
1959Merycoidodon Toohey
1968Blickohyus Schultz and Falkenbach
1968Genetochoerus Schultz and Falkenbach
1968Otionohyus Schultz and Falkenbach
1968Paramerycoidodon Schultz and Falkenbach
1968Merycoidodon Schultz and Falkenbach p. 33 figs. Figure 1-3, 51 (skulls, mandibles, and dentitions), 19-23 (limb elements)
1968Paramerycoidodon Schultz and Falkenbach p. 86 figs. igures 6--9, 52 (skulls, mandibles, and dentitions), 19-23 (limbs)
1968Otionohyus Schultz and Falkenbach p. 106 figs. Figures 10, 11, 52 (skulls, mandibles, and dentitions), 19-23 (limbs)
1968Genetochoerus Schultz and Falkenbach p. 135 figs. Figures 14-16, 52 (skulls, mandible, and dentitions), 19--23 (limbs)
1996Merycoidodon Stevens and Stevens p. 514
1998Blickohyus Lander
1998Prodesmatochoerus Lander
2007Merycoidodon Stevens and Stevens p. 158

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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.

C. B. Schultz and C. H. Falkenbach 1949 (Promesoreodon)SKULL:Small, decidedly smaller than in any known species of Mesoreodon,ranging in basal length from 185 to 194 mm., in width from 112 to 132 mm.; low and wide; supraoc- cipital produced posteriorly; lateral wings not widely spread; exoccipital foramina pre- sent; sagittal crest light and high; brain case well inflated; frontals wide; nasals moder- ately robust; anterior nasal-maxilla contact above P1 ; malar moderately deep below the orbit; zygomatic arch light, with inward notch posterior of the orbit; infraorbital foramen above P 8 ; lacrimal fossa of moderate size, moderately deep (deeper than in examples of Mesoreodon);slight depression on side of face above PLP 2 ; muzzle robust; occipital con- dyles medium sized; paroccipital process wide at base; bulla well inflated and high; post- glenoid process from moderately robust to robust, peg-like in outline; posterior palate projecting slightly beyond M1•
MANDIBLE:Light; ramus increasing in depth rapidly posteriorly; inferior border of ramus straight with rapid downward curve below anterior of M1 ; ascending ramus high.
DENTITION: Lighter and more brachyodont than in Mesoreodon.
LIMBS: Short and light.
C. B. Schultz and C. H. Falkenbach 1954 (Prodesmatochoerus)SKULL: Medium size; basal length ranging from 155 to 184 mm., width from 80 to 100 mm.; dolichocephalic; supraoccipital high and narrow, lateral wings not widely spread, produced posteriorly beyond occipital condyles; exoccipital foramina small and oblong in outline (no vacuities in prominent pit as in Subdesmatochoerus); sagittal crest moderately high and light; brain case elongated; frontals narrow; nasals long and narrow, with pointed to rounded posterior border and with slight anterior retraction; anterior nasal- maxilla contact above C/; orbits rounded, moderately large, looking mostly outward; zygomatic arch with abrupt posterior rise; malar moderately deep below the orbit, deepest point below middle of orbit; infra- orbital foramen above anterior portion of P3 ; lacrimal fossa large and moderately deep; small facial depression in area above PLP 3 ; muzzle narrow; premaxillae touching but not definitely fused; occipital condyles of medium size, widely spaced; paroccipital process with excavated external surface; bulla very small (minute in contrast to those of Subdesmatochoerus); postglenoid process light, wide laterally, with moderately steep slope on external border; glenoid surface arched; posterior palate projecting posteriorly for slight distance beyond M3.
MANDIBLE: Medium size; ramus shallow; postsymphysis in region below P 8 ; inferior border with gradual downward curve below and posterior to M3; ascending ramus moderately high, robust posterior border; condyle light, set at less than right angle to axis of dentition, external border farther forward and slightly higher than internal border.
DENTITION: Brachyodont, approximately equal to examples of Subdesmatochoerus, definitely more brachyodont than in Desma- tochoerus; dental series shorter than in the latter genus, approximately equal to those of S. socialis, and long in relation to length of skull; inferior and superior premolars rather large, not crowded, set approximately parallel to alveolar border; external styles of superior molars moderately prominent; C/ and P1 varying in size from comparatively small to large (similar to those of Merychyus); PLP 8 each usually with weak anterior intermediate crest; P4 may or may not have an external anterior pit; Pa with weak posterior intermediate crest.
LIMBS: Moderate length; smaller and lighter than in Subdesmatochoerus.
C. B. Schultz and C. H. Falkenbach 1954 (Subdesmatochoerus)SKULL: Small to medium size; basal length ranging from 175 to 215 mm., width from 94 to 125 mm.; dolichocephalic to submesocephalic; supraoccipital wings not widely spread, produced posteriorly beyond the occipital condyles; exoccipital vacuities present; sagittal crest moderately high; brain case elongated; frontals narrow; nasals with noticeable tapering posteriorly, also anteriorly, slight anterior retraction; anterior nasal-maxilla contact above P 1 ; orbits slightly oval vertically, with long axis sloping upward anteroposteriorly; zygomatic arch with moderately abrupt rise posteriorly from below the orbit, with inward notch posterior to orbit; squamosal moderately light; malar moder- ately deep below the orbit; infraorbital foramen above pa; lacrimal fossa moderately large and deep; slight facial depression in area above P1 to midline of pa (anterior to infraorbital foramen); muzzle narrow; premaxillae touching, but not definitely fused; occipital condyles of medium size; paroccipital process wide at base, with noticeable external notch, triangular in outline at contact with bulla; bulla inflated, laterally compressed; postglenoid process robust, with tendency to be wide laterally as it is antero-posteriorly, steep slope to external border; posterior palate even with last lobe of M3 to slightly posterior of M 8.
MANDIBLE: Medium size; postsymphysis in region below P 2 and Pa; inferior border of ramus parallel to alveolar border, with gradual downward curve posterior to Ma; ascending ramus moderately high, posterior border robust; condyle set at less than right angle to axis of dentition, with external border of condyle farther forward and higher than internal border.
DENTITION: Brachyodont, more so than in examples of Desmatochoerus; series longer than examples of Prodesmatochoerus (with exception of those of P. socialis dakotensis) and shorter than in Desmatochoerus; C/ and P1moderately large; /C two to three times the size of Ia; premolars large, usually crowded, p1-p 2 and P2 set at slight angle to alveolar border; external styles of superior molars prominent; p1-ps each with anterior intermediate crest; P 8 with posterior intermediate crest.
LIMBS: Tendency to be slightly longer than examples of Prodesmatochoerus meekae; lighter and shorter than examples of Desmatochoerus and D. (Paradesmatochoerus).
C. B. Schultz and C. H. Falkenbach 1968Small size; basal lengths ranging from 160 to 208 mm., widths from 99 to 130 mm. ; dolichocephalic; facial region moderately high; supraoccipital wings extending posteri- orly for short distance beyond condyles, with lateral wings moderately spread ( not fan- shaped as in Miniochoerinae) ; sagittal crest moderately high; brain case long and narrow; frontal wide (not reduced as in Desmatochoeri- nae) ; nasals light to moderately heavy, with considerable individual variation, especially in width ; posterior border of nasals acute, obtuse, or truncated; nasal-maxilla anterior contact in area above posterior portion of C/; supraorbi-
tal foramen from near to comparatively distant from midline of skull; orbits semiround and of medium size, looking outward, forward, and slightly upward; malar shallow (deeper in ex-
amples of M. macrorhinus) below orbit, inferior border with sharp upward curve posteriorly; zygomatic arch moderately light; lacrimal fossa moderately deep [more so than in examples of M. ( AnomerycQidodon), decidedly less depth than those of Eporeodontinae], oval to round; infraorbital foramen in area above pa ; muzzle slightly inflated ; premaxillae not fused ; oc- cipital condyles moderately light; paroccipital process moderately light, anterior-external area excavated; bulla small (minute) [differing from the well-inflated bulla of examples of M. (Anomerycoidodon)], similar to all oreodonts from "Zone C" of Chadron or "Zone A" of Brule, except inflated ones of Leptaucheniinae from latter zone; postglenoid process from moderately light to semirobust, wider trans- versely than anteroposteriorly, external border sloping down and inward, comparatively long vertically ( considerable individual variation) .
MANDIBLE: Moderately light; postsymphysis in area below Ps-P,; ramus moderately deep; inferior border of ascending ramus with in- ward curve (less noticeable in other lines of subfamily); condyle moderately large (lighter than in examples of Paramerycoidodon).
DENTITION:Light (lighter than examples of Paramerycoidodon and its subgenera, heavier than those of Genetochoerus and Otionohyus and their subgenera) ; C/ long and more or less robust; P1-pa each with weak to prominent anterior intermediate crest.
LIMBS: Moderately long and somewhat heavy, longer than examples of Miniochoerinae. (Examples with five digits on forefoot.)
M. S. Stevens and J. B. Stevens 1996Medium-sized oreodonts with steep premaxillae and arched nasal profiles; infraorbital foramen primitively located above p2 that migrates to above P4 in later species; the preorbital fossae, enlarged and deep in early species, becomes more pit-like and shallower in late examples; the zygomatic arch is unspecialized; the braincase is elongated with a narrow, protracted nuchal crest; the auditory bullae are initially small but become more inflated and lose their hyoidal grooves in later species; the premolars are umeduced with P 1-P4tP1-M3 ratio from 50% to 48% (rounded averages; Table 3); the average APM3/TM3 ratios are near 1.00 (Table 5); M3s are brachydont with APM3/Ht. M3 averages from 1.80 to 1.67 (Table 4) though low extremes (1.4-1.5) are submesodont, and TM3/Ht. M3 ratios progressively decrease (Table 6) from 1.80 (oldest) to 1.63 (youngest), as M3 becomes higher crowned relative to the width. Of pertinent genera, Merycoidodon differs from Miniochoerus Schultz and Falkenbach (1956) by a progressively larger size and lack of thinned enamel on the premolar- molar middle crests and selenes. Merycoidodon differs from Mesoreodon Scott (1893) in its smaller size, with slightly less reduced premolars, significantly broader molars in proportion to height (Table 6), APM3 22- 23% longer than APM3 (compared to 14% for Mesoreodon; Miniochoerus resembles Merycoidodon in this stereotypical aspect), and a more arched nasal profile. Merycoidodon differs from Eporeodon by its slightly larger size, relatively smaller auditory bullae, and higher, more convex nasal profile and broader frontals.