Daphoenictis tedfordi, Hunt, 1974

Boardman, GS & Hunt, RM Jr., 2015, New material and evaluation of the chronostratigraphic position of Daphoenictis tedfordi (Mammalia, Carnivora, Amphicyonidae), a cat-like carnivoran from the latest Eocene of northwestern Nebraska, USA, Palaeontologia Electronica (Hagerstown, Md.) 8 (5), pp. 1-10 : 2

DAPHOENICTIS TEDFORDI Hunt, 1974

( Figure 1 )

Referred Specimen. UNSM 27015 (field no. 1523- 62) ( Figure 1 ). Partial right hemimandible with canine, root of p1, partial p2, p3–m2, root of m3.

Locality and Stratigraphic Context. Initially reported as approximately 2 miles west of Orella and 1 mile northwest of [UNSM collecting district] Sx-41, T34N, R53W, section 31, Sioux County, Nebraska [see Site of Collection], White River Group, Big Cottonwood Creek Member, Chadron Formation. Found 10 ft above base of an algal limestone in proximity to brontothere and equid remains.

Age. Middle Chadronian NALMA, latest Eocene.

Holotype. NMC 9205, left hemimandible with p2– p4, m2, and damaged m1, Locality 133, Chadronian deposits of the Cypress Hills, Saskatchewan, Canada ( Russell, 1972, figure 13A, B; Hunt, 1974, p.1032).

Description. The partial hemimandible preserves the majority of the mandibular body, which contains the canine, roots of the p1 and m3, partial p2, and p3–m2, and a part of the ascending mandibular ramus. The canine is slender and recurved with a fine enamel ridge creating a cutting edge along the distal surface and a weaker ridge at the mesiolingual face. Preserved directly distal to the canine is the broken root of the p1, which was single-rooted. The double-rooted p2 is missing most of the crown, so cusp morphology cannot be described, but the general occlusal outline of this tooth matches that of other specimens described by Hunt (1974). Premolars, p3–p4, are blade-like, narrow teeth with accessory and cingulum cusps producing a leaflike appearance in both lingual and buccal views. The p3 is taller, but mesiodistally shorter than the p4, opposite of that seen in Daphoenus and Brachyrhynchocyon . The distal accessory cusp is well developed on the p 3 in contrast to other early amphicyonids ( Daphoenus , Daphoenodon ). Though not as tall and more robust, the p4 is morphologically similar to the p3, each with a distal accessory cusp, and mesial and distal cingular cusplets. The lower carnassial, m1, is highly diagnostic of the genus. The metaconid of the m1 is extremely reduced and the paraconid is advanced, placed nearly directly mesial to the protoconid. There is a marked notch between paraconid and protoconid. The m1 trigonid is much larger than the diminutive talonid; the talonid is reduced to a single centrally placed, knob-like hypoconid. The m2 is about half the length of the m1. The m2 trigonid is larger than the talonid and is dominated by a rather blunt protoconid, with a highly reduced paraconid. The metaconid is absent. The talonid of the m2 has a single centrally placed cusp, a hypoconid, similar to the m1. The m1 hypoconid, m2 protoconid, and m2 hypoconid form a mesiodistally aligned row of low blunt cusps useful for crushing. The mesiobuccal corner of the m2 is protuberant, as mentioned by Hunt (1974).

Measurements of UNSM 27015 (length x width in mm): canine, 7.2 x 4.8; p2, 7.6 x 3.0; p3, 9.9 x 4.0; p4, 10.4 x 4.5; m1, 15.2 x 7.0; m2, 7.2 x 4.8; p2–m2, length, 48.8.

Figures

FIGURE 1. Right hemimandible of Daphoenictis tedfordi (UNSM 27015) with canine, p3-m2, and broken base of p2 and single-rooted p1, middle Chadronian, Chadron Formation, section 31, T34N, R53W, Orella 7.5-minute topographic quadrangle, Sioux Co., Nebraska. 1, buccal view; 2, lingual view; 3, occlusal view.