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Megoreodon grandis

Mammalia - Merycoidodontidae

Taxonomy
Promerycochoerus grandis was named by Douglass (1907). Its type specimen is CMN 990, a partial skeleton (a .skull with mandible, cervical and lumbar vertebrre, a femur, a humerus, portions of a scapula, a radius, an ulna, a pelvis and a tibia.), and it is a 3D body fossil. Its type locality is Canyon Ferry Reservoir Earl Douglass Location, which is in a Hemingfordian terrestrial horizon in Montana. It is the type species of Megoreodon.

It was recombined as Promerycochoerus montanus grandis by Thorpe (1937); it was synonymized subjectively with Merycochoerus superbus by Lander (1998) and Tabrum and Nichols (2001); it was recombined as Megoreodon grandis by Schultz and Falkenbach (1940), Schultz and Falkenbach (1954), Morgan and Lucas (2003), Stevens and Stevens (2007) and Stevens et al. (2023).

Synonyms
Synonymy list
YearName and author
1907Promerycochoerus grandis Douglass p. 104 figs. Pl. 27
1907Promerycochoerus hollandi Douglass p. 106
1921Promerycochoerus lulli Thorpe p. 231 figs. 1A, B
1934Promerycochoerus loomisi Schlaikjer
1937Promerycochoerus gregoryi loomisi Thorpe p. 122 figs. pl. 13, figs. 1-2; pl. 46, fig. 2
1937Promerycochoerus hollandi Thorpe p. 124 figs. Fig. 8 ; PL X, fig. 2; PI. XV, figs. 4-5
1937Promerycochoerus lulli Thorpe p. 130 figs. Figs. 85-88
1937Promerycochoerus montanus grandis Thorpe p. 139 figs. Figs. 4, 96; PI. XVIII
1940Megoreodon grandis Schultz and Falkenbach
1954Megoreodon fricki Schultz and Falkenbach p. 167 figs. 1-3, 23-25
1954Megoreodon grandis Schultz and Falkenbach p. 168
1954Megoreodon grandis loomisi Schultz and Falkenbach p. 171 figs. 1-3, 18, 23-25
1954Superdesmatochoerus lulli Schultz and Falkenbach p. 215 figs. 16-18, 23, 25
1968Megoreodon hollandi Skinner et al.
1970Megoreodon hollandi Macdonald
2003Megoreodon grandis Morgan and Lucas p. 472 figs. Figures 2D - G
2007Megoreodon grandis Stevens and Stevens p. 160
2023Megoreodon grandis Stevens et al. pp. 72 - 73 figs. Figure 54; Appendix 6B; Table A25

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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
subfamilyPromerycochoerinae
genusMegoreodon
speciesgrandis()

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.

Megoreodon grandis Douglass 1907
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Invalid names: Megoreodon fricki Schultz and Falkenbach 1954 [synonym], Promerycochoerus hollandi Douglass 1907 [synonym], Promerycochoerus loomisi Schlaikjer 1934 [synonym], Promerycochoerus lulli Thorpe 1921 [synonym]
Diagnosis
ReferenceDiagnosis
M. R. Thorpe 1921 (Promerycochoerus lulli)Lacrymal fossæ very deep and large; skull long and slender; face narrow; orbits look chiefly outward, but slightly forward and not upward; infra-orbital foramina small and located above p4; sagittal crest very high and thin above posterior part of cranium, posteriorly curving over along the transverse crests, which are thin and close together; malar below orbit very thin but wide, posterior part of zygoma vertical, with crest rising nearly to the level of the squamous suture, and outer border rounded; masseteric fossre shallow; face deep; muzzle square; inferior incisors crowded; bullre large, extending to level of postglenoid processes; paramastoid and postglenoid processes very nearly close auricular fossa below; zygomatic arches originate above anterior portion of M2, with convexity extending forward for short distance; cranium parallel-sided up to squamous suture, in front of which is marked
groove; occiput above foramen magnum very narrow and convex, with exceedingly deep lateral fossæ.
C. B. Schultz and C. H. Falkenbach 1954 (Megoreodon fricki)SKULL:Smallest known of genus (considerably shorter than examples of M. grandis loomisi, geologic variety, from the same for- mation); brachycephalic; facial region short (considerably shorter than other species or subspecies of genus); supraoccipital wings with less posterior projection than in other forms of genus; nasals unusually broad and flaring in region of anterior nasal-maxilla contact (nasals long and narrow in other examples of genus with gradual posterior reduction in width from nasal-maxilla contact); infraorbital foramen 4 above anterior portion of P 4 ; lacrimal fossa pronounced; depression above premolar region very noticeable; occip- ital condyles light but widely spread; bulla more inflated than in other species of genus; postglenoid process higher and lighter than in average examples of genus.
MANDIBLE:More robust and shorter than in other species of genus; symphysis shorter than that of M. grandis loomisi; ascending ramus high and unusually narrow (antero-posteriorly); condyle lighter and smaller than found in other species of genus.
DENTITION: Less brachyodont than in other species of genus; series shorter than in other forms of the genus (series long for length of skull, extending posteriorly beyond orbit); short diastema between C/ and P 1 ; premolars very crowded and overlapping.
LIMBS: Approximately of same lengths and characters as in other examples of genus.
C. B. Schultz and C. H. Falkenbach 1954SKULL: Large and massive (larger than examples of M. fricki, tendency to be smaller than those of M. grandis loomisi); infraorbital foramen above posterior portion of P4.
MANDIBLE:Smaller than in average examples of M. grandis loomisi.
DENTITION:Series similar to those of examples of M. grandis loomisi.
LIMBS: Approximately equal to those of other forms of genus.
C. B. Schultz and C. H. Falkenbach 1954 (Superdesmatochoerus lulli)SKULL: Larger than examples of S. microcephalus; anterior nasal-maxilla contact above P 1 ; infraorbital foramen above posterior portion of P4.
MANDIBLE: Larger than examples of S. microcephalus; postsymphysis below P3.
DENTITION: Series longer than examples of S. microcephalus.
LIMBS: Within the size range of Megoreodon. (Known from tentatively referred specimen only.)
M. S. Stevens et al. 2023Giant oreodont, larger than any other species (M1-3 = 84-96 mm), with typical robust zygomatic arches of the Promerycochoerinae.
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 Late/Upper Oligocene to the top of the Hemingfordian or 28.40000 to 15.97000 Ma

Collections (12 total)


Time interval Ma Country or state Original ID and collection number
Geringian30.8 - 26.3USA (Nebraska) Megoreodon grandis (17595)
Geringian30.8 - 26.3USA (South Dakota) Megoreodon hollandi (17627)
Arikareean30.8 - 20.43USA (Idaho) Megoreodon grandis (17584)
Arikareean30.8 - 20.43USA (Wyoming) Megoreodon fricki (17472) Megoreodon grandis (17532) Promerycochoerus loomisi (17466)
Arikareean30.8 - 20.43USA (Nebraska) Megoreodon grandis (17569)
Late/Upper Oligocene28.4 - 23.03USA (New Mexico) Megoreodon grandis (31191)
Monroecreekian26.3 - 24.8USA (South Dakota) Megoreodon hollandi (17723 69921)
Harrisonian24.8 - 20.43USA (Nebraska) Megoreodon hollandi (17704)
Hemingfordian20.43 - 15.97USA (Montana) Promerycochoerus grandis (17885)