Leptocyon douglassi, TEDFORD R. H. & WANG X. & TAYLOR B. E., 2009

TEDFORD R. H., WANG X. & TAYLOR B. E., 2009, Phylogenetic Systematics Of The North American Fossil Caninae (Carnivora: Canidae), Bulletin of the American Museum of Natural History 2009 (325), pp. 1-218 : 19-22

Leptocyon douglassi , new species Figures 5, 6A–G, 7; appendix 3

Nothocyon geismarianus: Macdonald, 1970: 55 .

Type: NMNH 19931 (fig. 6C–E), cast AMNH 129685, partial palate with P4–M2 and left ramus with c and p2–m2 from the Toston Formation (early Arikareean), 2 2 miles southeast of Canyon Ferry, Lewis and Clark County, Montana.

Etymology: Named for Earl Douglass whose pioneering studies of the fossil mammals of Montana initiated modern knowledge of the Neogene faunas of the northern Rocky Mountains.

Referred Material: From the type area, Toston Formation (early Arikareean), Canyon Ferry , Lewis and Clark County, Montana: NMNH 19106 (cast AMNH 129684 ), fragments of immature skull and jaw including right partial ramus with p2 unerupted, dp3–dp4 and m2 unerupted, and left detached unworn m1. One mile east of Canyon Ferry : CMNH 1264, right and left mandibular rami with c–m3 (fig. 6A–B) ; and CMNH 1300, left ramus with i3 root, c–p3 alveoli, p4–m2, and m3 alveolus, Earl Douglass Collection, 1902.

White Sulfur Springs (early Arikareean), Meagher County, Montana: F:AM 54196 (fig. 6F–G), left ramus with c broken and p1 alveolus, p2–m3 from deposits considered temporally equivalent to the Gering Formation by Schultz and Falkenbach (1949: 145).

Wounded Knee–Sharps Fauna, Sharps Formation (early Arikareean), South Dakota: LACM 9371, left maxillary fragment with P4–M1 from LACM locality 1955 and referred to Nothocyon geismarianus by Macdonald (1970: 55); and LACM 9298, left maxillary fragment with M1 from LACM locality 1980.

UCMP locality V6377, Haystack 8, L-2, Turtle Cove Member, John Day Formation, between the Picture Gorge Ignimbrite and Deep Creek Tuff (29–28 Ma, early Arikareean): UCMP 79365, anterior part of skull lacking canines and incisors, P1 alveolus, P2 roots, left P3, left and right P4, M1–M2.

Distribution: Early Arikareean of Oregon, Montana, and South Dakota.

Diagnosis: Leptocyon douglassi differs from all other Arikareean species by its derived p3 lacking posterior cusp, m2 with long talonid (.90% of trigonid length), and absence of m2 paraconid. Additionally, it differs from L. vulpinus in its smaller size and relatively narrower and lower crowned premolars; from L. gregorii in averaging smaller in size, M2 having metaconule, and P4 of greater width with stronger protocone; and from L. mollis in its smaller size and proportionally smaller M1 and M2.

Description and Comparison: The p2–p4 are widely spaced, elongate, slender, and moderately tall crowned. The lower premolars of the type ramus ( NMNH 19931) and those of a referred ramus (F: AM 54196) have stronger anterior cingular cusps than in the type specimens of L. gregorii and L. vulpinus (compare figs. 6A–E with 11A–E and 8A–C). The anterior cusp is noticeably stronger on p3 and p4, and even the p2 of F:AM 54196 shows a small but distinct anterior cusp. Prominent anterior cingular cusp on the premolars is shared with Hesperocyon and members of the Borophaginae . On the other hand, the loss of a posterior cusp on P3 is a derived feature of this early Leptocyon species. The P4 of the type ( NMNH 19931) is transversely thick with a large protocone and a weak parastylar shelf, similar to that of the type of L. mollis and L. vulpinus but unlike the slender upper carnassial of L. gregorii . The M1 is proportionally smaller than in L. mollis (fig. 5) but morphologically similar with an extremely low-crowned paracone and metacone, strong labial cingulum, and a strong parastyle. The M2 is also proportionally smaller than in the type L. mollis (fig. 5), but it is morphologically similar with an extremely low-crowned paracone and metacone, strong labial cingulum, and a strong parastyle. The M2 is also proportionally smaller than in the type and has a very lowcrowned paracone and metacone, a welldeveloped protocone, and a strongly recurved talon. The m1 is slender with a strong metaconid and a somewhat more basinlike talonid than in L. gregorii . The elongate m2 with a very long talonid contrasts with the shorter talonid length of the m 1 in L. gregorii and L. vulpinus . The m2 has a relatively large subequal protoconid and metaconid but lacks the distinct paraconid present in the type of L. vulpinus .