Leptocyon matthewi, 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 : 43-46

Leptocyon matthewi , new species Figure 7, 17, 18A–F; appendices 3, 4

Vulpes species : Gregory, 1942: 348.

Type: F:AM 25198, mandible with right and left i1–m3 (fig. 18A–B), from Bear Creek Quarry (late Clarendonian) of Skinner and Johnson (1984), Ash Hollow Formation, strata approximately equivalent to the Merritt Dam Member, Cherry County, Nebraska.

Etymology: Named in honor of W. D. Matthew in recognition of his fundamental work on the Canidae .

Referred Material: Big Springs Canyon, undifferentiated beds (early Clarendonian) of the Ogallala Group, temporally younger than the Valentine Formation but earlier than the Ash Hollow Formation of adjacent Nebraska, UCMP locality V3322, site 2, Bennett County, South Dakota: UCMP 33426 and 33427, two partial rami listed by Gregory (1942: 348) and UCMP 32342, right partial ramus with c broken–p4 (p2–p3 broken).

Undifferentiated beds (early Clarendonian), Ogallala Group, temporally equivalent to the Thin Elk Gravels, Hollow Horn Bear Quarry, Todd County, South Dakota: F:AM 49433, posterior part of skull ; F:AM 49426, right isolated P4; F:AM 49434, left partial ramus with p4– Ma ; F:AM 49435*, right ramus with m2 and all alveoli; F:AM 49411*, left partial ramus with m2; F:AM 49446*, left partial ramus with p2; F:AM 49440, left radius distal cap missing; F:AM 49441, left femur (fig. 9F); F:AM 494441A, left distal part of tibia ; F:AM 49443, right metacarpal III; and F:AM 49443A, left partial metatarsal IV.

Thin Elk or Mission Gravel Pit, Thin Elk Gravels (early Clarendonian), Mellette County, South Dakota: F:AM 72701B, left distal part of humerus.

Clayton and East Clayton Quarry , basal Merritt Dam Member of the Ash Hollow Formation ( Medial Clarendonian ), Brown County, Nebraska: F:AM 49167, right partial ramus with p3 broken–m2 ; F:AM 49166, right partial ramus with m1–m2: F:AM 49168, left partial ramus with m1–m2; F:AM 49173, left m1; F:AM 49169, left partial ramus with p2 root–m1 alveolus, m2; F:AM 49171, right partial toothless ramus; F:AM 72707, right partial humerus; and F:AM 72708, right ulna.

Quinn Rhino Quarry 1, Cap Rock Member of Ash Hollow Formation (early Clarendonian), Brown County, Nebraska: F:AM 25130, left partial ramus with p1 alveolus–m2 (p4 and m3 alveoli).

Merritt Dam Member, Ash Hollow Formation (medial and late Clarendonian), Brown and Cherry counties, Nebraska: F:AM 62891, right m1, Gallup Gulch Quarry. F:AM 62881, left partial ramus with p1– p4 roots and M1 broken, Bolling Quarry. F:AM 49175*, right partial ramus with c, p1 alveolus, p2–p3 and p4–m2 alveoli: F:AM 62882*, left partial ramus with c–p1 alveoli, p2, p3–p4 aleoli; UNSM 5025-89, left m1, Pratt Quarry. F:AM 25193, left partial maxilla with P4–M1 ( Fig. 18C–D); F:AM 25156, left partial ramus with m1, Xmas Quarry. F:AM 49165, right partial ramus with p2–m2 Leptarctus Quarry (fig. 18E–F). F:AM 25194, left partial ramus with m1–m2 both broken, Kat Quarry. F:AM 25199, left partial ramus with m1–m2, from the talus of high channel with which Platybelodon barnumbrowni occurred, west side of Snake River about 1 mile below falls.

Bluejay Quarry ( UNSM locality Ap 112). Ash Hollow Formataion (late Clarendonian) in an unnamed post-Cap Rock Member channel, Antelope County, Nebraska. UNSM 47375, left ramus with p1 alveolus, p2, p3 roots, p4–m1.

Laucomer Meber of the Snake Creek Formation (late Clarendonian), Sioux County, Nebraska: AMNH 22039, right ramus with c alveolus–m2 (p1 alveolus and p2–p3 broken), Kilpatrick Pasture Quarry 7. AMNH 20053*, right ramus with c–p4 alveoli, m1 broken, m2, m3 alveolus, Kilpatrick Pasture Quarry b.

Round Mountain Quarry: Chamita Formation (early Clarendonian), Rio Arriba County, New Mexico: F:AM 62811, right ramus with i3–m2 (c broken, p1 alveolus, and m1 broken); F:AM 62806, fragmentary skull with P4–P2; F:AM 62808, left partial maxilla with P4–M1; F:AM 62813, left partial ramus with p3 broken and m1–m2 and associated right (less worn) m1 broken–m2; F:AM 62810*, right M1, broken M2 and metatarsals III, IV and V; F:AM 62812, mandible with c broken–m2 (p1–p4 broken); F:AM 62814, right partial ramus with c–m2 (p3 alveolus and p4 broken); F:AM 62815, left ramus with c broken–m3 (m1 broken); F:AM 62807, right partial maxilla with P3 broken– M2; F:AM 62817, left partial ramus with m1 broken–m3; F:AM 62816, left ramus with i3– p1 alveoli and p2–m2 (all broken); and F:AM 62818, right partial ramus with m1–m2.

Fish Lake Valley ( UCR locality RV 7407), Esmeralda Formation (early Clarendonian), Esmeralda County, Nevada: UCR 17005, right and left mandibular rami with i2–m3 (c broken), maxilla fragment with P1, P4 broken, right maxilla fragment with broken M1, left isolated M1, left broken isolated M2, and isolated broken teeth including a canine, premolar and incisors; and UCR 17006, right and left mandibular rami with i1–m2 (i–I2 broken), two isolated incisors, proximal parat of metacarpal II, metacarpal I, scapho-lumar, and a second phalanx.

Distribution: Clarendonian of Nebraska, South Dakota, New Mexico, Arizona and Nevada.

Diagnosis: Differs from L. vafer in m1 significantly larger without any overlap of confidence interval (fig. 7); m1 with larger and taller crowned hypoconid, entoconid enlarged, coalescing with base of hypoconid to close talonid basin, hypoconulid shelf present; and m2 smaller relative to length of m1 (fig. 17) with stronger anterolabial cingulum that extends more posteriorly.

Description and Comparison: Not all of the characters listed in the diagnosis can be found in every specimen but a combination of these characters readily distinguishes L. matthewi from L. vafer . As is characteristic of Leptocyon , a strong crest (postprotocrista) unites the M1 protocone and metaconule in L. matthewi (F:AM 25193, fig. 18D) and the metaconule is usually smaller than that Vulpes stenognathus . Associated remains from Fish Lake Valley ( UCR 17005) include an M1 with the parastyle smaller, the buccal cingulum weaker and the paracone noticeably higher crowned than the metacone than seen in either L. vafer or V. stenognathus . A fragment of the M2, showing most of the talon of UCR 17005 gives the only evidence in this taxon of the nature of the postprotocrista and metaconule of M2. The crista is present, but the conule seems lacking as in L. vafer . The m1 is also taller crowned than in L. vafer and sometimes (as in UCR 17005) approaches the crown height of this tooth in V. stenognathus . Unlike that of L. vafer , the m1 entoconid (F:AM 25199 and UCR 17005) is a larger and more distinct cusp resembling that of Vulpes stenognathus . The m1 hypoconulid shelf, which is absent in L. vafer , is sometimes developed in L. matthewi . Although in most specimens it is less developed. The m 2 in L. matthewi is shorter relative to the length of the m1 than in L. vafer (fig. 17), but the most notable difference is the stronger anterolabial cingulum that often extends more posteriorly than in L. vafer . The m 2 in L. matthewi , however, lacks the derived morphology characteristic of V. stenognathus and most mesocarnivorous living fox species that includes a stronger anterolabial cingulum and an enlarged metaconid which changes the occlusal outline of this tooth to labially concave and lingually convex.

Compared to V. stenognathus , the bulla (F: AM 49433) in L. matthewi is larger relative to the size of the cranium, and the lip of the auditory meatus is smaller and projects less laterally. In L. matthewi the paroccipital process is transversely narrow, short and its free tip projects posteroventrally in contrast to the broad structure with laterally projecting free tip in V. stenognathus and other Vulpes species. Furthermore, the limbs referred to L. matthewi lack the derived features of V. stenognathus . A humerus (F: AM 72707) referred to L. matthewi bears an entepicondylar foramen that is lacking in V. stenognathus , and a referred ulna (F: AM 72708) is much shorter and more robust than that of the latter.

Although the size of the dentition and the morphology of the first upper and lower molars of L. matthewi tend to be somewhat intermediate between those of Leptocyon and Vulpes , it lacks any derived features of the auditory bullae, paroccipital process, premolars, m2, and limbs that characterize V. stenognathus and other foxes.