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Merycoides longiceps

Mammalia - Artiodactyla - Merycoidodontidae

Taxonomy
Mesoreodon longiceps was named by Douglass (1907). Its type specimen is AMNH 9732, a partial skeleton (A nearly complete skull with the mandible, the cervical, lumbar, and sacral vertebrae, portions of most of the dorsal vertebrae, a scapula, a pelvis, a femur, a), and it is a 3D body fossil. Its type locality is North Boulder Valley, which is in a Harrisonian terrestrial horizon in the Renova Formation of Montana.

It was recombined as Pseudodesmatochoerus longiceps by Schultz and Falkenbach (1954); it was recombined as Merycoides longiceps by Loomis (1924), Schlaikjer (1934), Lander (1998), Tabrum and Nichols (2001) and Stevens and Stevens (2007).

Synonymy list
YearName and author
1907Mesoreodon longiceps Douglass p. 811 figs. 1 - 5
1924Merycoides longiceps Loomis
1934Merycoides longiceps Schlaikjer
1954Pseudodesmatochoerus longiceps Schultz and Falkenbach p. 207 figs. 12-15, 23-25
1998Merycoides longiceps Lander
2001Merycoides longiceps Tabrum and Nichols
2007Merycoides longiceps Stevens and Stevens p. 163

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RankNameAuthor
kingdomAnimalia()
Triploblastica
Nephrozoa
Deuterostomia
phylumChordataHaeckel 1847
subphylumVertebrata
superclassGnathostomata
Osteichthyes()
Sarcopterygii
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda()
Reptiliomorpha
Anthracosauria
Batrachosauria()
Cotylosauria()
Amniota
RankNameAuthor
Synapsida()
Therapsida()
infraorderCynodontia()
Epicynodontia
infraorderEucynodontia
Probainognathia
Mammaliamorpha
Mammaliaformes
classMammalia
orderArtiodactyla()
suborderTylopoda()
superfamilyOreodontoidea
familyMerycoidodontidaeThorpe 1923
subfamilyEporeodontinae
genusMerycoides
specieslongiceps()

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.

Diagnosis
ReferenceDiagnosis
E. Douglass 1907Skull long,especially the posterior portion; braincase large and full; nasals and frontals arching; sagittal crest sessile, represented by a small low ridge, median pillar of occiput broad; space between paroccipital and post glenoid processes unusually large; palate produced considerably posterior to last molar; teeth but slightly hypsodont
C. B. Schultz and C. H. Falkenbach 1954SKULL: Medium size; smallest known form of the genus; supraoccipital wings comparatively small, more widely spread than in examples of P. hoffmani and P. milleri; sagittal crest similar to examples of P. milleri, medial depression on sagittal crest less pronounced than in P. hoffmani; brain case more inflated, rounder, and shorter than in latter two species; nasals shorter and wider than in other species of genus (anterior nasal-maxilla contact farther down on the side of the face than in other forms of genus), anterior retraction less than in P. hoffmani, more so than in P. wascoensis; anterior nasal-maxilla contact above posterior portion of P 1 ; posterior portion of zygomatic arch comparatively light (similar to supposed female examples of P. hoffmani and P. milleri), lighter than in holotype of P. wascoensis, posterior border with less posterior rise than in two former species (more like P. wascoensis in this respect); infraorbital foramen above posterior portion of P8; lacrimal fossa larger and deeper than in other species of the genus; facial vacuity questionable; occipital condyles similar to examples of P. hoffmani and P. milleri, lighter than P. wascoensis,· paroccipital process similar to that of P. milleri; bulla suggesting a form similar to that of P. hoffmani (large and with some lateral compression); postglenoid process peg-shaped, light, and high; posterior palate projecting posteriorly for longer distance beyond M3 than in examples of other species of this genus.
MANDIBLE: Postsymphysis below p3; posterior border of ascending ramus comparatively robust; condyle larger than in P. milleri, approximately equal to that of P. hoffmani.
DENTITION: Smallest known series of genus; lighter than examples of P. hoffmani and P. milleri (similar to those of P. wascoensis in this respect) ; diastema between P1 and P2 shorter than in other examples of the genus.
LIMBS:Within size range of examples of P. hoffmani.