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Mesoreodon minor

Mammalia - Merycoidodontidae

Taxonomy

Promerycochoerus minor was named by Douglass (1903). Its type specimen is CM 769, a partial skull (Anterior portion of skull with I2-M3, partial mandible with i1-m3, and fragments), and it is a 3D body fossil. Its type locality is Lower Cabbage Patch Beds, which is in an Arikareean terrestrial horizon in the Renova Formation of Montana.

It was recombined as Promerycochoerus hollandi minor by Thorpe (1937); it was recombined as Promerycochoerus (Pseudopromerycochoerus) minor by Schultz and Falkenbach (1949); it was recombined as Eporeodon minor by Lander (1998); it was recombined as Mesoreodon minor by Stevens and Stevens (1996), Tabrum and Nichols (2001) and Stevens and Stevens (2007).

Synonyms

Desmatochoerus (Paradesmatochoerus) grangeri was named by Schultz and Falkenbach (1954). Its type specimen is F:AM 33303, a partial skeleton (Skull with I1-M3, mandible with i1-m3, 2 femora (1 partial), 2 tibiae, partial pes, and vertebrae), and it is a 3D body fossil. Its type locality is Little Muddy Creek (Niobrara County), which is in an Arikareean terrestrial horizon in Wyoming.

It was synonymized subjectively with Mesoreodon minor by Stevens and Stevens (1996); it was synonymized subjectively with Eporeodon major by Lander (1998).
Desmatochoerus macrosynaphus was named by Riel (1964). Its type specimen is MSU 0940, a partial skull (a mandible with i2-m3; partial upper dentition including right P3 -M3 , left C, P2 , P3 , M3), and it is a 3D body fossil. Its type locality is Lower Cabbage Patch Beds, which is in an Arikareean terrestrial horizon in the Renova Formation of Montana.

It was synonymized subjectively with Mesoreodon minor by Stevens and Stevens (1996); it was synonymized subjectively with Eporeodon minor by Lander (1998).
Desmatochoerus (Paradesmatochoerus) monroecreekensis was named by Schultz and Falkenbach (1954). Its type specimen is F:AM 37551, a partial skeleton (Skull with l1(br.)-M3, mandible with i1-m3, partial femur, partial tibia, vertebrae, and pelvis), and it is a 3D body fossil. Its type locality is Big Muddy Creek, which is in an Arikareean terrestrial horizon in Wyoming.

It was synonymized subjectively with Mesoreodon minor by Stevens and Stevens (1996).
Desmatochoerus (Paradesmatochoerus) sanfordi was named by Schultz and Falkenbach (1954) [definitely the correct spelling]. Its type specimen is F:AM 45443, a partial skull (Partial skull with I1-M3 and right ramus with i1(alv.)-m3 (i3 rt., /c alv., and p1 br.)), and it is a 3D body fossil. Its type locality is Joe Sanford Ranch, which is in an Arikareean terrestrial horizon in Nebraska.

It was synonymized subjectively with Mesoreodon chelonyx by Stevens and Stevens (1996); it was synonymized subjectively with Merycoides relictus by Lander (1998); it was synonymized subjectively with Mesoreodon minor by Stevens et al. (2023).
Desmatochoerus (Paradesmatochoerus) wyomingensis was named by Schultz and Falkenbach (1954). Its type specimen is F:AM 33312, a skull (Skull with I1-M3 and mandible with i1-m3), and it is a 3D body fossil. Its type locality is Willow Creek, which is in an Arikareean terrestrial horizon in Wyoming.

It was synonymized subjectively with Mesoreodon minor by Stevens and Stevens (1996); it was synonymized subjectively with Eporeodon major by Lander (1998).
Eporeodon cheeki was named by Schlaikjer (1934). Its type specimen is MCZ 17765, a partial skeleton (Skull with I1-M3, mandible with i1-m3, and most of skeleton), and it is a 3D body fossil. Its type locality is Sixty Six Mountain (Upper), which is in an Arikareean terrestrial horizon in the Harrison Formation of Wyoming.

It was recombined as Eporeodon major cheeki by Thorpe (1937); it was recombined as Mesoreodon cheeki by Schultz and Falkenbach (1949) and Black (1961); it was synonymized subjectively with Mesoreodon minor by Stevens and Stevens (1996); it was synonymized subjectively with Eporeodon latidens by Lander (1998).
Mesoreodon scotti was named by Schlaikjer (1934). Its type locality is Big Muddy Creek, which is in an Arikareean terrestrial horizon in Wyoming.

It was recombined as Mesoreodon cheeki scotti by Schultz and Falkenbach (1949); it was synonymized subjectively with Mesoreodon minor by Stevens and Stevens (1996); it was synonymized subjectively with Eporeodon latidens by Lander (1998).
Pseudodesmatochoerus wascoensis was named by Schultz and Falkenbach (1954). Its type specimen is AMNH 7827, a partial skull (Partial skull with I1-I3 alv. and C/(rt.)-M3), and it is a 3D body fossil.

It was synonymized subjectively with Mesoreodon minor by Stevens and Stevens (1996); it was synonymized subjectively with Eporeodon minor by Lander (1998).

Synonymy list

Year	Name and author
1903	Promerycochoerus minor Douglass
1934	Eporeodon cheeki Schlaikjer
1934	Mesoreodon scotti Schlaikjer
1937	Eporeodon major cheeki Thorpe p. 76 figs. PL VII; PI. XXXIX, fig. 2
1937	Mesoreodon scotti Thorpe p. 103 figs. PI. XLIV, fig. 2
1937	Promerycochoerus hollandi minor Thorpe p. 127 figs. Fig. 83; PI. XVI
1949	Promerycochoerus (Pseudopromerycochoerus) minor Schultz and Falkenbach p. 124 figs. 10, 12
1949	Mesoreodon cheeki Schultz and Falkenbach p. 135 figs. 7, 15, 17-19, 25
1949	Mesoreodon cheeki scotti Schultz and Falkenbach p. 137 figs. Figures 15, 16, 18, 19, 25, 26
1954	Desmatochoerus (Paradesmatochoerus) grangeri Schultz and Falkenbach p. 194 figs. 8-11, 24-25
1954	Desmatochoerus (Paradesmatochoerus) monroecreekensis Schultz and Falkenbach p. 195 figs. 8 - 11
1954	Desmatochoerus (Paradesmatochoerus) sanfordi Schultz and Falkenbach p. 197 figs. 8 - 11
1954	Desmatochoerus (Paradesmatochoerus) wyomingensis Schultz and Falkenbach p. 199 figs. 8 - 11, 18
1954	Pseudodesmatochoerus wascoensis Schultz and Falkenbach p. 210 figs. 12 - 14
1961	Mesoreodon cheeki Black
1964	Desmatochoerus macrosynaphus Riel p. 3 figs. text-fig. no. 2; plates I, II
1970	Promerycochoerus minor Macdonald
1996	Mesoreodon minor Stevens and Stevens
1998	Eporeodon minor Lander
2001	Mesoreodon minor Tabrum and Nichols
2007	Mesoreodon minor Stevens and Stevens p. 160

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Rank	Name	Author
kingdom	Animalia	()
—	Bilateria
—	Eubilateria	Ax 1987
—	Deuterostomia
phylum	Chordata	Haeckel 1874
subphylum	Vertebrata
superclass	Gnathostomata
—	Osteichthyes	()
subclass	Sarcopterygii	()
subclass	Dipnotetrapodomorpha	(Nelson 2006)
subclass	Tetrapodomorpha	()
—	Tetrapoda
—	Reptiliomorpha
—	Anthracosauria
subclass	Amphibiosauria	Kuhn 1967
—	Cotylosauria	()
—	Amniota
subclass	Synapsida
—	Therapsida	()
infraorder	Cynodontia	()
—	Mammaliamorpha

Rank	Name	Author
—	Mammaliaformes
class	Mammalia
—	Theriamorpha	(Rowe 1993)
—	Theriiformes	()
—	Trechnotheria
—	Cladotheria
—	Zatheria
subclass	Tribosphenida	()
subclass	Theria
—	Eutheria	()
—	Placentalia
—	Boreoeutheria
—	Laurasiatheria
—	Scrotifera
—	Euungulata
—	Artiodactylamorpha
—	Artiodactyla	()
family	Merycoidodontidae
subfamily	Merycoidodontinae
genus	Mesoreodon
species	minor	()

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.

†Mesoreodon minor Douglass 1903

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Invalid names: Desmatochoerus (Paradesmatochoerus) grangeri Schultz and Falkenbach 1954 [synonym], Desmatochoerus (Paradesmatochoerus) monroecreekensis Schultz and Falkenbach 1954 [synonym], Desmatochoerus (Paradesmatochoerus) sanfordi Schultz and Falkenbach 1954 [synonym], Desmatochoerus (Paradesmatochoerus) wyomingensis Schultz and Falkenbach 1954 [synonym], Desmatochoerus macrosynaphus Riel 1964 [synonym], Eporeodon cheeki Schlaikjer 1934 [synonym], Mesoreodon scotti Schlaikjer 1934 [synonym], Pseudodesmatochoerus wascoensis Schultz and Falkenbach 1954 [synonym]

Diagnosis

Reference	Diagnosis
C. B. Schultz and C. H. Falkenbach 1949 (Mesoreodon cheeki)	SKULL:Medium size, approximately equal to the average examples of M. chelonyx; lighter construction than that of M. megalodon sweeti; sagittal crest not so high as that of M. megalodon sweeti, but approximately equal to that of M. chelonyx; zygomatic arch light, approximately equal to that of M. chelonyx, but with posterior border not extending so far posteriorly as in M. megalodon sweeti; lacrimal fossa smaller and shallower than that in M. chelonyx; postglenoid process not so robust as in M. megalodon sweeti. MANDIBLE: Similar to that of M. chelonyx; lighter then that of M. megalodon sweeti. DENTITION:Length of dental series same as in M. chelonyx. LIMBS: Equal in size to those of M. chelonyx, smaller than average examples of M. megalodon.
C. B. Schultz and C. H. Falkenbach 1949	SKULL:Small, smallest known species of the subgenus; nasals slightly retracted; anterior nasal-maxilla contact above the region of P1; zygomatic arch light, extending posteriorly slightly beyond the postglenoid proc- ess; infraorbital foramen above posterior portion of P'; lacrimal fossa small and shallow; paroccipital process tapering rapidly downward; bulla of medium size, inflated, and suboval in outline; postglenoid process almost as wide laterally as anteroposteriorly and with a sloping external border. MANDIBLE: Small; similar to that of examples of other species of the subgenus. DENTITION: Series small, equal to that of P. (P.) minor pygmyus; smaller than in other species of the subgenus. LIMBS:Unknown.
C. B. Schultz and C. H. Falkenbach 1954 (Desmatochoerus (Paradesmatochoerus) grangeri)	SKULL: Medium size; longest known of subgenus; width similar to examples of D. (P.) monroecreekensis and D. (P.) wyomingensis, wider than those of D. sanfordi; submesocephalic; facial region longer than other ex- amples of subgenus; sagittal crest slightly higher than in other species of subgenus (not so high as examples of Desmatochoerus) ; exoccipital vacuities smaller and nasals with more anterior retraction than in other species of subgenus; posterior portion of zygomatic arch robust, more so than in examples of D. (P.) monroecreekensis, infraorbital foramen above anterior portion of P 3 ; bulla with more lateral compression and posterior palate projecting more posteriorly than in other forms of subgenus. MANDIBLE: Similar to those of other species of subgenus; postsymphysis below Pa; ascending ramus higher than in examples of D. (P.) wyomingensis. DENTITION: Lighter than in other species of subgenus; superior series extending to the midline of orbit, not so far posteriorly as in other forms of subgenus. LIMBS:Longer but similar to other examples of subgenus.
C. B. Schultz and C. H. Falkenbach 1954 (Desmatochoerus (Paradesmatochoerus) monroecreekensis)	SKULL: Medium size [average examples equal in length to those of D. (P.) wyomingensis, slightly shorter than in D. (P.) grangeri]; more robust and wider than D. (P.) wyomingensis; submesocephalic; exoccipital vacuities intermediate in size between examples of D. (P.) wyomingensis and D. (P.) grangeri; anterior nasal-maxilla contact above P1; zygomatic arch moderately robust (lighter in female examples); infraorbital foramen above posterior portion of P3 to anterior portion of P4 ; paroccipital process more robust, bulla with less vertical height, and postglenoid process more massive and wider laterally than in D. (P.) wyomingensis. MANDIBLE: Slightly more robust than in examples of D. (P.) wyomingensis; post-symphysis below posterior portion of Pa; ramus with tendency to be deeper below the anterior edge of Ma than later species. DENTITION:Similar to examples of D. (P.) wyomingensis, lighter than in D. (P.) grangeri. LIMBS: Similar to examples of D. (P.) wyomingensis; shorter than those of D. (P.) grangeri.
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 (Desmatochoerus (Paradesmatochoerus) wyomingensis)	SKULL: Approximately same length but narrower and lighter than examples of D. (P.) monroecreekensis, smaller than in the holotype of D. (P.) grangeri, larger than in D. (P.) sanfordi; dolichocephalic; exoccipital vacuities larger than in other known forms of subgenus; anterior nasal-maxilla contact above middle of P1 ; infraorbital foramen above pa; base of paroccipital process heavier, postglenoid process more robust, and bulla with greater vertical length than in examples of D. (P.) monroecreekensis. MANDIBLE: Similar to examples of D. (P.) monroecreekensis, but lighter and with less depth below Ma; postsymphysis below P3. DENTITION: Approximate size of examples of D. (P.) monroecreekensis; greater length and more robust than in D. (P.) grangeri and D. (P.) sanfordi. LIMBS: Similar in size and form to exam- ples of D. (P.) monroecreekensis.
C. B. Schultz and C. H. Falkenbach 1954 (Pseudodesmatochoerus wascoensis)	SKULL: Approximately same length as examples of P. hojfmani and P. milleri, larger than that of P. longiceps; mesocephalic, wider than other examples of genus; lower than in other species of genus, but not so low as examples of Mesoreodon (some of vertical compression of skull may be due to crushing); supraoccipital wings larger and with more lateral spread than in other species of genus; brain case inflated but slightly depressed; frontals wide; nasals more robust than usual in this genus, less anterior retraction than in P. hoffmani; anterior nasal-maxilla contact above anterior portion of P 1 ; less posterior rise of zygomatic arch than in other species of genus (arch incomplete); malar moderately deep below orbit; lacrimal fossa comparatively small but deep; occipital condyles more widely spread than in other species of genus; paroccipital process more massive and with less lateral compression than usual in this genus; bulla large, larger than in P. milleri, similar to that of P. hoffmani except for less lateral compression; postglenoid process robust; posterior palate projecting posteriorly beyond M 8 , not to extent found in the holotype of P. longiceps. MANDIBLE:(Unknown). DENTITION: Series lighter than in examples of P. hoffmani and P. milleri, approximately equal to those of P. longiceps; series of less length than in two former species and longer than in latter. LIMBS:(Unknown).
S. J. Riel 1964 (Desmatochoerus macrosynaphus)	Medium size; alveolar length of lower dental series approximately 135 mm; mandible very long and narrow; elongate symphysis extending to beneath Mi; ramus very shallow anterior to M 3 , increasing in depth posteriorly with abrupt downward curve of inferior border beneath M 3 ; dentition light as in D. (Paradesmatochoerus); superior premolars narrow; M3 with prom- inent metastyle; lower premolars not crowded; posterior acces- sory blade present on p3 ; anterior and posterior fossettes of p4 open lingually.