PBDB Taxon

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Phenacocoelus kayi

Mammalia - Merycoidodontidae

Taxonomy

Phenacocoelus kayi was named by Schultz and Falkenbach (1950). Its type specimen is F:AM 33660A, a partial skull (Skull with I1-M3 and partial mandible with i1-i3 alv. and /c-m3), and it is a 3D body fossil. Its type locality is Southeast of Lusk, which is in a Harrisonian terrestrial horizon in the Marsland Formation of Wyoming.

It was synonymized subjectively with Merycoides harrisonensis by Lander (1998).

Synonyms

Hypsiops luskensis was named by Schultz and Falkenbach (1950). Its type specimen is F:AM 44853A, a partial skeleton (skull, mandible, and probably associated postcranial elements), and it is a 3D body fossil. Its type locality is Eighteen Mile District, which is in a Harrisonian terrestrial horizon in Wyoming.

It was recombined as Phenacocoelus luskensis by MacFadden (1980); it was synonymized subjectively with Merycoides harrisonensis by Lander (1998); it was synonymized subjectively with Phenacocoelus kayi by Stevens et al. (2023).

Synonymy list

Year	Name and author
1950	Phenacocoelus kayi Schultz and Falkenbach p. 106 figs. 1-3,11,13-15
1950	Hypsiops luskensis Schultz and Falkenbach p. 122 figs. 4-6, 11, 13-15
1980	Phenacocoelus luskensis MacFadden p. 93
2023	Phenacocoelus kayi Stevens et al. pp. 99 - 202 figs. Figure 81; Appendix 10C; Table A35

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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	Ticholeptinae
genus	Phenacocoelus
species	kayi

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.

†Phenacocoelus kayi Schultz and Falkenbach 1950

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Invalid names: Hypsiops luskensis Schultz and Falkenbach 1950 [synonym]

Diagnosis

Reference	Diagnosis
C. B. Schultz and C. H. Falkenbach 1950 (Hypsiops luskensis)	SKULL: Approximately same length but narrower than H. breviceps, smaller than other species of genus; nasals retracted to area above P 1 ; anterior nasal-maxilla contact above anterior portion of P2 ; zygomatic arch elongated posteriorly and not extending upward as high as in other species of this genus, but similar to those of Phenacocoelus kayi and P. stouti (see discussion, p. 104); infraorbital foramen above anterior portion of P4; small, round, facial vacuity; other characters similar to those of H. brachymelis and H. brachymelis petersoni. MANDIBLE: Characters and outline typical of genus; postsymphysis below Pa. DENTITION:Shorter and lighter than in H. breviceps; smaller than examples of other known species of genus; p1-p 3 each with anterior intermediate crest; PrPa each with posterior intermediate crest. LIMBS:Similar to those of H. brachymelis; considerable individual variation in length but within the expected variation of a species.
C. B. Schultz and C. H. Falkenbach 1950	SKULL:Intermediate in size between P. typus and P. stouti; frontals slightly rounded laterally; nasals retracted anteriorly to a point above posterior portion of P1, with greater retraction than in examples of P. typus; anterior nasal-maxilla contact above the posterior portion of P2; supraorbital foramen at posterior end of a deep, narrow, elongated, slot-like depression (not an oblong vacuity as in P. typus or a round foramen as in P. stouti'), with suggestion of a groove extending forward and downward from it to facial vacuity; zygomatic arch with a gradual rise posteriorly, extending to a point above posterior border of postglenoid process; in- fraorbital foramen above posterior portion of P 8 ; facial vacuity 2 ; bulla with inferior surface more depressed towards basioccipital than in P. typus; postglenoid process moderately heavy with sloping external border. MANDIBLE:Intermediate in size between examples of P. typus and P. stouti; approximately equal in size to examples of Hypsiops luskensis. DENTITION: Superior and inferior series intermediate in over-all length between P. typus and P. stouti, approximately equal in size to examples of H. luskensis; C/ and P1 large; axis of PLP 3 parallel to alveolar border; P2 and Pa set at slight angle to alveolar border; P2 with weak posterior intermediate crest; Paand P, each with moderately prominent posterior intermediate crest. LIMBS:Decidely longer than examples of P. typus; lighter, but approximately same length as examples of P. stouti.
M. S. Stevens et al. 2023	Larger species of Phenacoelus (M1-3 length = 49-51 mm) (Fig. 82).