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Hypsiops breviceps

Mammalia - Artiodactyla - Merycoidodontidae

Taxonomy
Ticholeptus breviceps was named by Douglass (1907). Its type specimen is CM 1191, a partial skeleton (a skull, mandible, left humerus, left radius and ulna, right radius and part of the right humerus, a tibia, a fibula, a tarsus with two metatarsals, greater p), and it is a 3D body fossil. Its type locality is Woodin, which is in a Harrisonian terrestrial horizon in Montana.

It was recombined as Hypsiops breviceps by Schultz and Falkenbach (1950), Lander (1998), Tabrum and Nichols (2001) and Stevens and Stevens (2007).

Synonyms
Synonymy list
YearName and author
1907Ticholeptus breviceps Douglass p. 106
1907Ticholeptus brachymelis Douglass p. 815 figs. 6, 7
1923Ticholeptus petersoni Loomis
1950Hypsiops brachymelis Schultz and Falkenbach p. 116 figs. 4-6, 11, 13-15
1950Hypsiops breviceps Schultz and Falkenbach p. 120 figs. 4-6, 12-15
1950Hypsiops johndayensis Schultz and Falkenbach p. 123 figs. 4-6, 12
1998Hypsiops breviceps Lander
2001Hypsiops breviceps Tabrum and Nichols
2007Hypsiops breviceps Stevens and Stevens p. 160

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RankNameAuthor
kingdomAnimalia()
Triploblastica
Nephrozoa
Deuterostomia
phylumChordataHaeckel 1847
OlfactoresJefferies 1991
subphylumVertebrata
Gnathostomata()
Osteichthyes()
Sarcopterygii
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda()
Reptiliomorpha
Anthracosauria
Batrachosauria()
Cotylosauria()
RankNameAuthor
Amniota
Synapsida()
Therapsida()
infraorderCynodontia()
Epicynodontia
infraorderEucynodontia
Probainognathia
Mammaliamorpha
Mammaliaformes
classMammalia
orderArtiodactyla()
suborderTylopoda()
superfamilyOreodontoidea
familyMerycoidodontidaeThorpe 1923
subfamilyMerycochoerinae
genusHypsiops
speciesbreviceps()

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 1907 (Ticholeptus brachymelis)Skull high in proportion to length. Greatest height to greatest length, 157mm.: 257mm. = 61: 100 or approximately 3/5 Forehead only moderately broad; upper anteroposterior contour of skull nearly straight; sagittal crest short and not high; orbit small; zygomatic arches deep under the orbit, ascending posteriorly; squamosal portion of arch not heavy; nasals shortened; horizontal ramus of mandible moderately deep,uniform in height from p3 to m3; premolar teeth not long or high; molars moderately hypsodont; proportion of length of upper premolar to molar series= 48mm.: 60mm.= 80:100= 4/5,;lower molar to premolar series=49 mm.: 64 mm. = 76.5 :100; limbs and feet short. The premaxillaries are coossified for a distance of 12cm. The upper portion of the anterior narial opening is large and broadly rounded, the borders only moderately steep. The narials are abbreviated. The infra orbital foramen opens above the anterior portion of p-4. The malomaxillary ridge is heavy and the lachrymal pit deep. The malar is deep beneath the orbits and ascends backward. The squamosal portion of the zygomatic arch is heavy. The forehead is not extremely broad, neither is the occiput. The exoccipitals and the paroccipital processes are moderately expanded laterally. The internal portions of the latter, behind the tympanic bullae,are thickened antero-posteriorly. The bullae are quite large. The external auditory meatus is a long, straight tube directed upward more than outward or backward. The angle of the mandible is large but does not extend very much below the lower border of the horizontal ramus. The masseteric fossa is deep.
C. B. Schultz and C. H. Falkenbach 1950 (Hypsiops johndayensis)SKULL: Slightly longer and wider than ex- amples of H. brachymelis, definitely larger than those of H. breviceps and H. luskensis; more robust than those of other known species of genus; wider across frontals than in other species of genus; nasals with slight anterior retraction, less than in other species of genus; anterior nasal-maxilla contact above posterior portion of P1 ; zygomatic arch similar to that of H. brachymelis (light posterior border which may represent a female); malar not so deep below orbit as in last- named species, similar to that of H. brachymelis petersoni; lacrimal fossa deep and large; infraorbital foramen above anterior portion of P4; occipital condyles much larger than in other known species of genus; bulla more inflated and extending farther downward than in H. brachymelis, postglenoid process more massive and with external border less steep than in other species of genus.
MANDIBLE: Similar to that of H. brachymelis in size; inferior border of ramus with more marked downward curve posterior to first lobe of Ma than in H. brachymelis; ascending ramus very high with sharp inward curve of inferior border and with prominent fold on internal, inferior border (apparently for attachment of muscles). (Postsymphysis unknown.)
DENTITION: Series approximately same length as those of H. brachymelis; P2 and pa with anterior intermediate crest; inferior series similar to those of H. brachymelis. (Inferior series known from PrMa only.)
LIMBS:Similar to examples of H. brachymelis. (Known from referred fragmentary examples only.)
C. B. Schultz and C. H. Falkenbach 1950 (Hypsiops brachymelis)SKULL: Larger than those of Hypsiops breviceps and H. luskensis, slightly larger than average examples of H. brachymelis petersoni, somewhat smaller and less massive than those of H. johndayensis; mesocephalic; nasals retracted anteriorly to area above anterior of P 1 ; anterior nasal-maxilla contact above P 2 ; posterior portion of arch somewhat U-shaped in outline from side view, with sharp rise of inferior border; posterior border of arch extending posteriorly to anterior border of postglenoid process; malar deep below orbit; infraorbital foramen above anterior border of P4•
MANDIBLE:Same size comparisons as in skull; postsymphysis below midline of Pa.
DENTITION:C/ large; /C approximately twice the size of Ia, spatulate shape in outline; premolars crowded (worn in holotype, but suggesting presence of anterior intermediate crest on P2 and P3) ; P3 with suggestion of posterior intermediate crest.
LIMBS: Slightly longer than known examples of other species of genus (H. johndayensis known from fragmentary examples only).
C. B. Schultz and C. H. Falkenbach 1950SKULL: Smaller than examples of H. brachymelis, approximately same length but wider than H. luskensis; brachycephalic, more so than in other species of genus; supra-occipital wings (damaged in holotype, only known specimen) suggesting less posterior extension than in H. luskensis; anterior nasal-maxilla contact above middle of P2; infraorbital foramen above posterior portion of P8; deep lacrimal fossa
MANDIBLE: Similar to H. brachymelis, but of smaller size; postsymphysis below P3.
DENTITION: More hypsodont than in other species of genus; series almost as long as those of H. brachymelis; cheek teeth con- siderably heavier than in H. luskensis and similar to those of H. brachymelis; superior and inferior premolars crowded; PLP 8 each set at an angle to alveolar border; anterior intermediate crest on p1-paclose to externalborder of teeth; P1-Pa each set at an angle to alveloar border; Pa with posterior intermediate crest.
LIMBS: Similar to examples of H. luskensis; smaller than those of holotype of H. brachymelis.