Leptocyon sp. B

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 : 26-43

Leptocyon sp. B

Material: F:AM 97247, right partial ramus with p2–p4 alveoli, and m1 (measurements, table 5) from a roadcut at the halfmile point between Sect. 28 and Sect. 33, T25N, R52W, Box Butte County, Nebraska. The jaw was collected from deposits that were mapped by Cady and Scherer (1946: pl. 1) as the Marsland Formation. Ted Galusha (personal commun., 1975) reported that the lithology at this site is unlike that of the Marsland Formation, and regional stratigraphic considerations suggest a late Hemingfordian or possibly early Barstovian age for this specimen.

Discussion: The length of the m1 is only 8 mm. It is thus the second smallest known specimen referred to the genus. The m1 is derived with respect to that of L. delicatus in that the trigonid is more open and longer relative to the length of the talonid, and the paraconid is less acute. The m1 talonid appears narrow as in L. delicatus , but a closer examination shows that postmortem erosion of the lateral surface is partly responsible for this narrowing. The horizontal ramus is slender and extremely shallow, but less elongate than the slightly larger jaw refered to L. douglassi (CM 1300) from early Arikareean deposits of Canyon Ferry, Montana. The m1 is slender and morphologically similar to the larger jaws of L. gregorii (F: AM 49063) from rocks referred to the Harrison Formation of Wyoming. As in the latter, the trigonid of m1 is long relative in the length of the tooth, the protoconid is tall, the metaconid is moderately developed, and the talonid is relatively short, with the entoconid being markedly smaller than the hypoconid.

Leptocyon gregorii (Matthew), 1907 Figures, 3, 5, 7, 10A–F, 11A–E, 17;

appendices 2, 3

Nothocyon gregorii Matthew, 1907: 183 , fig. 1. Hesperocyon gregorii: Macdonald, 1963: 206 .? Tomarctus sp. indet.: Macdonald, 1970: 57.

Type: AMNH 12879, posterior two-thirds of a skull with P3–M2, right and left mandibular fragments with p3 and m1–m2 (fig. 11A–E) and limb fragments. Matthew recorded the type from 1 mile east of Porcupine, lower Rosebud beds, South Dakota. Macdonald (1963: 206) listed the type locality as ‘‘A.M.N.H. ‘Rosebud’ 19’’ from rocks thought to be equivalent to the Harrison Formation of Nebraska.

Referred Material: Type area, west of Window Butte, LACM locality 2012, identified as the Harrison Formation (medial Arikareean), South Dakota: LACM 9198, right partial ramus with c, m1 (p1 alveolus and p2–p4 broken), described and measured by Macdonald (1970: 57–58).

Lusk area, rocks referred to the middle Harrison Formation (medial Arikareean), Niobrara County, Wyoming: F:AM 49063, skull with C broken–M2 and left and right mandibular rami with c broken–m3 (fig. 10A–F), north of Keeline, middle brown sand. F:AM 49062, immature right partial ramus with dp3–dp4, m1 unerupted, north of Keeline. North Ridge, along Highway 85, about 10 miles north of Lusk: F:AM 49059, right ramal fragment with m1. North of Jeriah: F:AM 49061, right ramus with c, p1 alveolus, p2–m2.

Distribution: Medial Arikareean of South Dakota and Wyoming.

Revised Diagnosis: L. gregorii differs from L. vulpinus in smaller size; slender P4, weaker M1 parastyle; smaller premolars; less robust m1 with trigonid and talonid narrower relative to length; and proportionally smaller m2. Differs from L. leidyi and L. vafer in smaller dentition, retention of m2 paraconid, and proportionally longer and more inflated bullae. L. gregorii differs from L. vafer in narrower cranium with greater cerebellar exposure, retaining postparietal foramina; weaker m2 anterolabial cingulum; and m2 with subequal protoconid and metaconid.

Description and Comparison: The dentition of L. gregorii is significantly smaller than that of L. vulpinus (fig. 7) and only slightly smaller than that of L. leidyi . Leptocyon gregorii retains such primitive features as the paraconid on m2, the postprotocristid (but not metaconule) on M2 and a posterior cusp on p3.

The skull features of L. gregorii are provided by the incomplete skull of the type ( AMNH 12819, fig. 11A–E) and a referred skull (F:AM 49063, fig. 10A–F). These skulls are compared with the type skull ( UNSM 25715, fig. 11F–I) of L. leidyi and several heretofore undescribed skulls of L. vafer . Crushing and weathering has obscured some of the details of the braincase of the type skull but the description is complemented by the features of the better preserved referred skull. Viewed dorsally, the shape and proportions of the postorbital cranium of L. gregorii are similar to those of Hesperocyon . As in Hesperocyon , the cranium of L. gregorii is elongate relative to the length of the skull and it retains a small postparietal foramina. Elongation of the cranium approximates that of the type of L. leidyi . The nasals converge to a point at the midline well behind (3 mm) the most posterior position of the maxillaryfrontal suture in the referred skull. The frontals are narrow and only slightly elevat- ed, and the postorbital processes are weak. Marked postorbital constriction is present in both skulls of L. gregorii as in the type of L. leidyi . In L. vafer the frontals are relatively wider and the postorbital constriction is less. Although the dorsal surface of the braincase is broken in the type of L. gregorii , weak lyrate temporal crests can be seen joining behind the frontoparietal suture to form a low sagittal crest. In the referred skull (F: AM 49063) the temporal crests are very weak and best seen where they unite at a point just posterior to the frontoparietal suture. Despite crushing it is evident that the braincase in L. gregorii is narrower and the cerebellar exposure is greater than in L. vafer . Other measurements of the braincase in the types of L. gregorii and L. leidyi cannot be made because of crushing.

The auditory bulla in L. gregorii is anteroposteriorly longer and relatively larger and more inflated than in either L. leidyi or L. vafer . Because the bulla is badly broken in the type of L. leidyi , little can be determined except for its gross size, which is smaller than that of L. gregorii . In the latter, the anterior border of the bulla and the eustachian opening are slightly anterior to the postglenoid process, whereas in L. leidyi the broken surface indicates that the entotympanic bone reaches only to the posterior surface of the postglenoid process. Anteriorly, the bulla in L. gregorii is marked by a prominent depression at the junction of the ectotympanic and the entotympanic bones. The paroccipital process in L. gregorii is nearly vertical, but short and without a free tip. It covers only a small area of the bulla surface. In L. vafer this process is also vertical but it is wider and its free tip extends more ventrally; the anterior surface is deeply concave and covers a wider area of the posterior wall of the bulla.

Leptocyon leidyi , new species Figures 7, 11F–I, 12C–J, 13A–F, 17; appendices 2–4

Leptocyon vafer (Leidy) : Matthew, 1918: 190 (in part).

Leptocyon sp. : Galusha, 1975: 56–57.

Type: UNSM 25715, partial skull with I3– M2 (fig. 11F–I), from Hemingford Quarry 12D (early Hemingfordian), Box Butte County, Nebraska. The type was reported by the University of Nebraska State Museum to be from the upper part of the Marsland Formation. We consider these specimens to be from the Runningwater Formation in accordance with McKenna (1965 [as in ref]: 10) in that ‘‘the type Runningwater Formation is part of the same unit as that referred to as Upper Marsland by Schultz and others.’’

Etymology: Named in honor of Joseph Leidy, pioneering vertebrate paleontologist, who described the genotypic species of Leptocyon .

Referred Material: From the Runningwater Formation (early Hemingfordian) in the general area of the type, Box Butte County, Nebraska: UNSM 25454 , right ramus with c, p1–p2 roots, p3–m2, m3 alveolus (fig. 12C–E), Hemingford Quarry 12D ; UNSM 25716 , left partial ramus with p2–m2 (p3 broken), locality 31, an extension of Hemingford Quarry 12D ; UNSM 26146 , left isolated M1 and UNSM 26145 , left ramal fragment with m1, Hemingford Quarry 7 .

Pebble Creek, Runningwater Formation (early Hemingfordian), Dawes County, Nebraska: F:AM 67994C, calcaneum.

From the Runningwater Formation (early Hemingfordian) on the east side of Dry Creek, Box Butte County, Nebraska: F:AM 97245, left partial ramus with p3 alveolus, p4–m1, m2 alveolus.

Middle of the Road Quarry, Red Valley Member, Box Butte Formation (late Hemingfordian), Box Butte County, Nebraska: F:AM 96688, right partial ramus with p4, m1 broken, m2 root ( Galusha, 1975: 56).

Sheep Creek Formation (Late Hemingfordian), Sioux County, Nebraska: F:AM 54450, left ramus with p2, p4–m2, and c–p1, p3 and m3 alveoli (fig. 12F–G), Hilltop Quarry. F:AM 54451, right partial ramus with m1– m2, Thistle Quarry. F:AM 54452, right partial ramus with m1. F:AM 67790, right tibia, Greenside Quarry. F:AM 54453, right partial ramus with m1–m2, East Ravine Quarry. F:AM 72671, left femur, Thompson Quarry.

Olcott Formation (early Barstovian), Sioux County, Nebraska: F:AM 54380, palate with I1–M2 (fig. 12H); F:AM 54376, right ramus with p3–m2 (p4–m1 broken), New Surface Quarry. F:AM 54375, mandible with i1–m3 (fig. 12I–J), Echo Quarry. F:AM 54377, right partial ramus with p3–m3; F:AM 72673, right radius, New Surface Quarry. F:AM 72672, right radius; F:AM 72673A, left partial radius; F:AM 72674, right tibia; F:AM 67817, right metatarsal II, Echo Quarry. F:AM 54378, right ramus with c broken– m3, Jenkins Quarry. F:AM 54379, right partial ramus with m1–m2, Humbug Quarry. AMNH 17201, right ramus with p4–m2, Lower Snake Creek beds (referred to L. vafer by Matthew, 1918: 190).

Observation Quarry (early Barstovian),?Sand Canyon Formation, Dawes County, Nebraska: F:AM 25344, left partial ramus with p1–m1.

Lower Madison Valley (early Barstovian), Montana: CMNH 739, right partial ramus with c broken–m1 (p1 alveolus).

Pawnee Creek Formation (early Barstovian), Weld County, Colorado: F:AM 28345, partial mandible with i3, c broken, p1–m1, m2 broken (fig. 13A–B), East Valley No. 1, east side pit.

Skull Ridge Member of the Tesuque Formation (early Barstovian), Santa Fe County, New Mexico: F:AM 27273, right and left partial rami with c broken–m2; F:AM 63134*, right toothless partial ramus, White Operation. F:AM 50177*, left ramal fragment with p4–m2 all broken, White Opertion area. F:AM 50162*, left partial ramus with c–m2 all broken or alveoli, near White Operation. F:AM 63135*, right partial ramus with c–p4 alveoli, m1 broken, m2 alveolus, District No. 1. F:AM 67891, proximal part of radius, and F:AM 67891A, proximal part of ulna, Skull Ridge.

Barstow Formation (early Barstovian), San Bernardino County, California: F:AM 27279, left partial ramus with m1 broken– m2, ‘‘Third Division.’’ F:AM 27274, c–m3 (p1 alveolus), no data, preservation suggestive of ‘‘Third Division.’’ F:AM 27537A, left partial maxilla with P3 broken–M2; and F:AM 27537, right partial ramus with p4– m3, Green Hills.

Barstow Formation (late Barstovian), San Bernardino County, California: F:AM 50112, left partial maxilla with P4–M2; F:AM 50116, left partial ramus with p4–m3 (m1 broken); F:AM 50110, left partial ramus with p1–m3; F:AM 50111, left ramus with p4–m2, Hidden Hollow Quarry. F:AM 27535, anterior half of skull with I1–M2 and right and left incomplete rami with c–p2 broken, p3–m2, m3 root (fig. 13C–F); F:AM 27536, right and left rami with p2–m3, North End. F:AM 50113, left partial ramus with p4 broken–m2 (m1 broken), Falkenbach horizon, North End. F:AM 50115, partial mandible with broken teeth, below Black Hill Quarry, North End. F:AM 27540, left isolated m1, Skyline Quarry. F:AM 50114, right ramal fragment with m1–m2 both broken, prospect near Chert Ridge. F:AM 27275, partial palate with P2 and P4–M2; F:AM 27276, right and left partial rami with p3 broken–m1; F:AM 27278, left patial ramus with p3 broken–m2, Hemicyon stratum. UCMP 35308, left M2 and right and left ramal fragments with c broken, p1–p2, p4, m1 broken, m2–m3 alveoli, from site 33, UCMP locality V3847. F:AM 27280, right partial ramus with p4 broken–m1, Second Division; and F:AM 27277, left partial ramus with p4–m1, questionably Second Division.

Tributary of Ellison Creek, about 0.75 mile northeast of Willow Grove (late Barstovian), Pine County, Nevada: NMNH 243776, partial palate with P2–P4 all broken and M1–M2.

Distribution: Early to late Hemingfordian of Nebraska, early Barstovian of Nebraska, Colorado, Montana, New Mexico, and California, and late Barstovian of New Mexico, Nevada, and California.

Diagnosis: L. leidyi differs from L. gregorii in dentition averaging slightly larger (fig. 7), proportionally shorter and less inflated bulla, and tendency to reduce and lose postprotocrista of M2, and loss of paraconid of m2. L. leidyi averages smaller than L. vafer with 95% confidence interval of m1 length nearly separated (fig. 7); m2 slightly longer relative to length of m1, it lacks enlargement of m2 anterolabial cingulum and short nasals that characterize L. vafer , but it shares lack of postprotocrista on M2.

Description and Comparison: The dentition of L. leidyi is similar in size to that of L. gregorii but smaller than that of L. vafer (fig. 7). The morphology of the dentition closely resembles that of L. gregorii and only the reduction and loss of the metaconule and postprotocrista on M2 and loss of the paraconid m2 distinguish the two taxa.

The type skull of L. leidyi closely resembles that of L. gregorii (fig. 11). In both skulls the nasals reach posteriorly beyond the frontalmaxillary suture; the frontals and the postorbital constriction are narrow; and the weak temporal crests unite near the frontoparietal suture to form a low sagittal crest. The basicranial region is shattered and our comparison is thus limited to size. Judging by the distance from the posterior lacerate foramen forward to the eustachian opening, the bulla was anteroposteriorly shorter than that of L. gregorii . Moreover, the preserved part of the tympanic bone indicates that it was also less inflated and the occipital bone between the bullae is relatively wider than that of L. gregorii . In the type skull of L. leidyi the anterior suture for the tympanic bone is behind the glenoid cavity, whereas in L. gregorii it is directly opposite the glenoid cavity. Although the auditory meatus is broken, it appears unlikely that the lip projected laterally to the extent seen in that of L. vafer .

In the upper dentition the P1–P3 are anteroposteriorly short, widely spaced, and without posterior cusps. The P4 has a weak parastyle and a well-developed protocone that is situated more anteriorly than that of the type of L. gregorii . A moderately strong lingual cingulum extends the full length of the tooth. The morphology of the M1 of L. leidyi is similar to that of the type of L. gregorii . It is characterized by a low-crowned paracone and metacone, a weak parastyle, and a moderately strong labial cingulum. M1 differs, however, from that of the type of L. gregorii in its more quadrate shape and in the reduction of the metaconule. M2 is relatively wider than that of L. gregorii , its metaconule is absent in late Hemingfordian examples of L. leidyi , and the postprotocrista is lacking as well in Barstovian samples as in L. vafer .

The lower dentition and mandible are closest in structure to those of L. gregorii where they differ only slightly in size. The mean length of m1 is not significantly different in these taxa (fig. 7). A larger size difference is present between L. leidyi and L. vafer where the observed ranges of m1 length broadly overlap but the 95% confidence intervals are nearly separated (fig. 7). Additionally, L. leidyi has a proportionally longer m2 relative to the length of m1, the premolars are lower crowned, shorter, and have less prominent cusplets, and the m1 talonid is low-crowned. L. leidyi shares with L. vafer the loss of m2 paraconid but is otherwise plesiomorphic in the lower dentition.

Discussion: The dentition of L. leidyi is similar in size to that of L. gregorii (fig. 17). The coefficients of variation for some teeth indicated in appendix 3 are high by most standards, probably due to the wide temporal and geographic range of the referred specimens. Examining the statistics, we find the coefficient of variation is high (nearly 10) for the anterior premolars (p1 and p2) and for the length and width of the second upper and lower molars. The sizes of the anterior premolars and the last molars at the ends of the toothrow are generally more variable and the coefficient of variation is often higher than teeth that have anterior and posterior occlusal constraints.

The morphology known for L. leidyi appears in most cases to be plesiomorphic with respect to L. vafer , and in this respect L. leidyi could be considered an approximation of the morphological features of the ancestral stock for later species of Leptocyon . It shares the loss of the postprotocrista on M2 with L. vafer , a synapomorphy that links those species within Leptocyon . Leptocyon gregorii , which appears only modestly distinguishable from L. leidyi in dental features, is clearly differentiated by its autapomorphy, the markedly inflated bulla.

Leptocyon vafer (Leidy), 1858 Figures 3, 7, 9C–E, G, H, 14G–H, 15A–G, 16A–G, 17, 52, 61A; appendices 2, 4

Canis vafer Leidy, 1858: 21 .

Vulpes vafer: Trouessart, 1897: 310 (catalog).

‘‘ Canis ’’ vafer: Matthew, 1909: 115 .

Leptocyon vafer: Matthew, 1918: 190 .

Canis vafer: Merriam, 1919: 533 , figs. 138A, 139B.

Canid indet.: Henshaw, 1939: 17, pl. 2, fig. 2, 2A.

Leptocyon vafer: Henshaw, 1942: 110 , pl. 3, fig. 6, 6A.

Vulpes vafer: Macdonald, 1948: 55 , fig. 1A–B.

Leptocyon vafer: Webb, 1969: 39 , fig. 7.

Type: NMNH 126, right and left rami, c broken, p1–m3 (p3 broken), figured by Leidy (1869: pl. 1, fig. 2, our fig. 14G–H). The type was collected in 1857 by the Warren and Hayden Expedition from the ‘‘Loup Fork beds’’ along the Niobrara River in Nebraska. According to the notes and diaries of Snowden, who accompanied the expedition, Warren and Hayden joined Snowden at the mouth of Bear Creek and continued down the Niobrara River to the vicinity of present day Norden, Nebraska. It is most likely that the type was collected from this section of the Niobrara River. Both the Ash Hollow and the Valentine formations are exposed along this part of the Niobrara River, but the preservation of the type suggests that it is from the Valentine Formation (M.F. Skinner, personal commun., 1972).

Referred Material: Norden Bridge Quarry (Univ. Nebr. locality Bw-106), Cornell Dam Member of the Valentine Formation (early late Barstovian), Brown County, Nebraska: UNSM 83958*, right ramus with c, p4–m2; NMNH 35296*, right ramus with p1–p3, p4 broken, m1–m2; NMNH 35291*, right ramus with m1–m2 (from Voorhies, 1990: A135).

Crookston Bridge Member of the Valentine Formation (early late Barstovian), Cherry County, Nebraska: UNSM 25717, partial skull with P2–M2; UNSM 25718, partial skull with P2–M2; UNSM 25718, partial skull with I1–M2 (C and P1 alveoli) and right ramus with i3–m3 (p1 alveolus, fig. 14A–D); UNSM 25793, left ramus with c–m2 (p1 and m3 alveoli); UNSM 25719, left ramus with c, m1–m2, and alveoli, Crookston Bridge Quarry. UNSM 32009, right ramus with c, p1–p4 broken alveoli, m1–m2, m3 alveolus, 40 ft above Crookston Bridge Quarry. F:AM 62876, right ramus with p3–m2, Railroad Quarry A. F:AM 25441*, right partial ramus with p4 and m2, Devil’s Jump Off Quarry. UCMP 63644, right partial ramus with p4– m1, m2 broken; UCMP 33127, left partial ramus with p1, p2–m1 all broken, and m3 alveolus, listed by Macdonald (1948: 55); UCMP 33126, right partial ramus with p1– m2, m3 alveolus, listed by Macdonald (1948: 55); UCMP 29209, right partial ramus with p3 broken, p4 alveolus–m2, m3 alveolus, listed by Macdonald (1948: 55), and associated left partial ramus with p4, m1 broken, and m3 alveolus; UCMP 29208, isolated teeth including left P4, right M1, left m1, and right m1, Fort Niobrara, UCMP locality V3218. UCMP 32016, isolated right m1, Little Beaver A, UCMP locality V3306. UCMP 29893, isolated right P4, Railway Quarry A, UCMP locality V3307. UCMP 63722, left partial maxilla with M1, boat landing locality. F:AM 62870, left ramus with p2–m2 (fig. 14E–F); F:AM 62871, right partial maxilla with P4–M2; F:AM 62874, left ramus with c broken–m2; F:AM 62888, right partial ramus with m1–m2; F:AM 25440, left partial ramus with m1–m2; F:AM 72706, left metatarsal V, Nenzel Quarry. F:AM 72704, right metatarsal II, F. Schoettger Ranch.

Annies Geese Cross Quarry, Crookston Bridge Member, Valentine Formation (early late Barstovian), Knox County, Nebraska: UGV 68a, right isolated M1; UGV 68b, right isolated P4; UGV 68c, right isolated broken m1; UGV 64, right partial ramus with p2, m1–m2, and alveoli of remaining cheek teeth; UGV 65, right partial ramus with m2, m3 alveolus; UGV 66, right partial maxilla with P4–M1 (both broken); UGV 67, left partial maxilla with M1 broken; UGV 70a, right isolated M1; UGV 70b, left isolated broken M1; UNSM 51951, right partial ramus with c root, p1 alveolus–m1; UNSM 51952, left partial ramus with m2 and alveoli for c–m3; UNSM 51953*, right isolated and broken m1; UNSM 51950, right radius (fig. 9D); and UNSM 51949, left tibia.

Devils Gulch Member of the Valentine Formation (medial late Barstovian), Brown, Cherry, and Keyapaha counties, Nebraska: F:AM 62880A*, left partial ramus with m1 broken–m2; F:AM 72703, left partial tibia, Meisner Slide. F:AM 72701D, left distal part of humerus, near head of Jones Canyon, Dutch Creek. F:AM 62872, left ramus with c–p3 all alveoli, p4–m1 broken–m3, Meisner Slide,?Burge or Devils Gulch Member. F:AM 62879, left ramus with p3–m2, Fairfield Falls Quarry.

Verdigre Quarry, basal sands Devils Gulch Member of the Valentine Formation (late Barstovian), Knox County, Nebraska: UW 2453, left partial ramus with p1–m2, m3 alveolus; UW 2454, left partial ramus with p4 alveolus and m1–m2, m3 alveolus; UW 2461, right partial ramus with p1–p4 alveoli, m1; UW 2464, left isolated m1; UW 2465, right isolated m1; UW 2466, right isolated m1, UW 2455*, right ramus with p1–p4 alveoli, m1–m2, m3 alveolus; UW 2456, left ramus with c, m2, and all alveoli; UW 2457, left partial ramus with m1 broken–m2 and m3 alveolus; UW 2458, m2 and p2–m1 alveoli; UW 2460, left partial ramus with m2; UW 2459*, left partial edentulous ramus; UW 2467, right isolated P4; and UW 2469, left isolated P4; CMNH 19679, left partial ramus with i1–p3 alveoli, p4–m1, and m2 broken alveolus; CMNH 19675, left detached m1; CMNH 19676, left detached m2; and CMNH 19678, right detached P4.

Valentine Formation (late Barstovian), Fort Niobrara, Cherry County, Nebraska: UNSM 25794, left partial maxilla with P3 alveolus–M2; UNSM 25408, left partial ramus with p1 alveolus–m2 (p2–p4 broken); AMNH 8548, right partial ramus with m1, m2 broken, and m3 alveolus; AMNH 8545, left partial ramus with c–p4 alveoli, m1 (broken)–m2, and m3 alveolus; and AMNH 8546, left partial ramus with p1 alveolus, p2, p3 alveolus, p4, and m1 broken.

Rattlesnake Canyon, Valentine Formation (late Barstovian), Brown County, Nebraska: F:AM 25137, right partial ramus with p4– m1.

Driftwood Creek area (late Barstovian), Virgil W. Hay Ranch, 5.5 miles E and 8 miles S of Trenton, Hitchcock County, Nebraska: F:AM 62901, left ramal fragment with m1– m2.

Burge Member of the Valentine Formation (earliest Clarendonian), Cherry, Brown, and Keyapaha counties, Nebraska: F:AM 62886, right partial ramus with p3–m2; F:AM 62887, right partial ramus with m1– m2; F:AM 62885, right partial ramus with p2–m2 (p4 broken); F:AM 62895, left ramus with m3 and all alveoli; F:AM 72702A, left partial ulna, Burge Quarry. F:AM 62884, left partial ramus with m1–m2; F:AM 72701A, left distal part of humerus, Lucht Quarry. F:AM 62889, right ramus with p2–m2 and all alveoli; F:AM 62877, right partial ramus with p4 broken–m1; F:AM 62878, left edentulous ramus, June Quarry. F:AM 62883*, left partial ramus with m2 and c–m1 alveoli, Midway Quarry. F:AM 25444, left ramus with c–m2 (p1, p4, and m3 alveoli, fig. 14I– J), McGuires Canyon. F:AM 62892, right ramal fragment with m2; UCMP 32229, left mandibular fragment with p1–p3 alveoli and p4–m1 (listed and figured by Webb, 1969: 40, fig. 7), Crazy locality. UCMP 64657, right mandibular ramus with c–m2, m3 alveolus (listed by Webb, 1969: 41), Fatigue Quarry. F:AM 72701, right humerus (fig. 9C), south side of Snake Den Canyon, east side of Snake River. F:AM 72702, right ulna (fig. 9E), northeast of falls of Niobrara River, near Cody. F:AM 72705, left metatarsal IV, Mogle Ranch.

Paleo Channel Quarry, temporally equivalent to the Burge Member of the Valentine Formation (earliest Clarendonian), Sheridan County, Nebraska: F:AM 62873, left partial ramus with m1–m2.

Undifferentiated beds (late late Barstovian) of the Ogallala group, Selby Ranch Quarry, 12 miles northeast of Phillipsburg, Phillips County, Kansas: F:AM 49452*, left partial ramus with p4–m1, m2 broken.

Pojoaque Member of the Tesuque Formation (late Barstovian, see Galusha and Blick, 1971: 110; Tedford and Barghoorn, 1993), Santa Fe and Rio Arriba counties, New Mexico: F:AM 62778, partial skull with I1– M1 all broken and partial left ramus with i1– m2 all broken; F:AM 62750, right immature ramal fragment with m1 and associated femur and tibia; F:AM 62756, partial palate with P3–M2; F:AM 62757 and 62757A, left partial maxilla with P4–M2 and left ramus with c broken, p2–p3 both broken, m2; F:AM 62758, right ramus with c broken and p4–m2; F:AM 62764, left partial ramus with m1–m2; F:AM 62763, skull with I1–P1 alveoli, P2–M2, and mandible with c–m3 (fig. 15A–D); F:AM 63136*, right partial ramus with m2 and alveoli, Pojoaque Bluffs. F:AM 62751, left ramus with c–m1 (p1 alveolus and p2–p3 broken); F:AM 62752, mandible with c–m3 all alveoli or broken, Central Pojoaque Bluffs. F:AM 30923*, left broken m1, Jacona Microfauna Quarry, west of Pojoaque Bluffs. F:AM 62754, left toothless maxilla; F:AM 62755*, partial cranium and right and left ramal fragments with m1 broken–m3, west of Pojoaque Bluffs. F:AM 27402C, left partial ramus with p4–m2, Cuyamunque. F:AM 62761, left ramal fragment with p3 broken–m1, West Cuyamunque. F:AM 27416, skull with P2–M2; F:AM 27402, mandible with i1–m3; F:AM 27402A, right partial ramus with p2 broken–m3 (p3– m1 broken); F:AM 27407, left ramus with c broken–m3 (p1 missing); F:AM 27412, palate with I1–M2 (fig. 61A, incisors) and left partial ramus with p4–m2; F:AM 27401, right partial maxilla with P4 broken–M2; F:AM 27417, right and left partial rami with c–m1; F:AM 27411A, right partial ramus with p3–m2 all broken; F:AM 27412A, left partial ramus with p4–m2; F:AM 27406, right ramus with m1–m2 and all alveoli; F:AM 62774, left partial ramus with p3–p4 (m1 broken); F:AM 27415, right ramus and left partial ramus with c broken–m3 (p4–m1 broken), Santa Cruz. F:AM 62760, left premaxilla and partial maxilla with I2–I3 and P4–M2, left ramus with i3–m3, c broken–p1 alveolus (fig. 15E–G); F:AM 27413, partial skull with P2 broken–M2; F:AM 27411, right ramus with p1–m2 (p2– p3 and m1 broken); F:AM 50201, left partial ramus with p3–m2 (all broken), Santa Cruz, First Wash. F:AM 27421, partial mandible with c root–p3 and p4–m2 (all broken), Santa Cruz, Second Wash. F:AM 50202A* and B*, right and left ramal fragments with p4–m1 (both broken) and m2, Santa Cruz, Third Wash. F:AM 62771, palate with p3–m2, Ojo Caliente. F:AM 62773, right ramus with p1– m2 (p3–p4 broken), middle Ojo Caliente locality. F:AM 62765, left partial ramus with p3–m2 (m1 broken), red layer, Santa Fe. F:AM 27410, left maxillary fragment with P4, Third District. F:AM 27411B, palate with P2–P3 both broken, P4–M2; F:AM 27409, partial palate with P4–M2 and right partial ramus with m1–m2 and alveoli; F:AM 62848*, left partial maxilla with P4 broken– M1; F:AM 27408, mandible with c–m3 (all broken or alveoli), no data except from Santa Fe area. F:AM 27422, right metatarsal III, Santa Cruz special layer. F:AM 67902, humerus, distal end missing, Santa Cruz red layer. F:AM 67902A, calcaneum; F:AM 27486, right partial humerus, Tesuque Quarry. F:AM 62780, articulated right tibia and left partial tibia and fibula, tarsals, metatarsals, and phalanges (fig. 9G–H), from 60 feet below blue-gray ash, central Pojoaque Bluffs. F:AM 62750, partial humerus, right immature femur and tibia lacking caps, tarsal bone, and fragments, west Pojoaque Bluffs.

Conical Hill Quarry, lower part of the Ojo Caliente Sandstone, Tesuque Formation (late Barstovian), 15 miles northwest of Española, Rio Arriba County, New Mexico: F:AM 62769*, left maxillary fragment with P4–M2; F:AM 62766, partial palate with P2–P3 (both broken), P4–M1 broken; F:AM 62768*, left M2; F:AM 62767, left ramus with c and p2–m2.

Santa Clara and North Santa Clara area, Pojoaque Member of the Tesuque Formation (late Barstovian and possibly Clarendonian), Santa Fe County, New Mexico: F:AM 62790, right and left rami with c (unerupted)–m3; F:AM 62790A, left edentulous ramus; F:AM 62791, left partial ramus with p4 broken–m2; F:AM 62792*, left immature partial ramus with c broken–dp4, north Santa Clara. F:AM 27414A, right maxilla with P1–M2; F:AM 27414, right partial maxilla with P4–M2; F:AM 27483, right and left partial rami with p4 broken–m3; F:AM 27404, right ramus with c broken–m2 (p2 and p4 broken); F:AM 27405, left partial ramus with m1–m2, Santa Clara. F:AM 62793*, left partial ramus with c–m1 (all broken) and p1 missing, lower beds, Santa Clara locality, northeast of Round Mountain Quarry.

San Ildefonso, upper part of Pojoaque Member of the Tesuque Formation (late Barstovian and possibly Clarendonian), Santa Fe County, New Mexico: F:AM 27420, left ramus with p3–m3; F:AM 27402A, left ramus with c broken–m2 (p2– m1 broken); F:AM 27402B, right and left partial rami with m1 broken–m2; F:AM 27403, left ramus with c broken–m3 (p1 alveolus and m1 broken); F:AM 62826, right and left partial rami, left with c broken, p1, p2–m2 all broken, m3, right partial ramus with c root, p1–p2 alveoli, p3 broken–p4; and F:AM 62824*, right partial ramus with c root, p1–p2 alveoli, p3 root, and p4.

Jemez Creek area, Cerro Conejo Formation (late Barstovian), Sandoval County, New Mexico: F:AM 50189*, left maxillary fragment with P3 and P4 broken M1 and M2 broken, left and right partial rami with c broken–m3 (p2–m2 broken or alveoli) and vertebrae, Canyada de Zia, greenish sand. F:AM 62779*, ramal fragment with p1–p4, and isolated teeth including P4 broken, M1, m1, two canines, and limb fragments including partial radius, partial ulna, right metacarpal IV, both metacarpals V, both calcanea, astragalus, and limb fragments, west tributary of Canyada de Zia, 40 feet above green zone at the top of first set of cliffs. F:AM 50163, right partial ramus, m1 broken–m2, Canyada de Zia, F:AM 50200, right and left partial rami with p3 broken– m3, Rincon Quarry. F:AM 31110, right partial ramus with m1, fourth tributary north of Prospect Fork west side of Canyada de Zia.

North Rio Puerco, Cerro Conejo Formation ( Tedford and Barghoorn, 1999, late Barstovian), Sandoval County, New Mexico: F:AM 62845, crushed partial skull with P3– M2; F:AM 62847*, immature right partial ramus with dp3–dp4, F:AM 62846, right partial maxilla with P4–M1, Ceja Prospect, near the head of north fork of Canyada Moquino. F:AM 62849, left ramus with symphysis, i1–p1 all broken, and p2–m2, near the top of red cliffs in Short North Fork of Canyada Moquino.

Siebert Formation (late early Barstovian), San Antonio Mountains, near Tonopah, Nevada: LACM ( CIT) 780, right and left rami with c–m2 (p4 broken); LACM ( CIT) 2815, partial ramus with p4–m2; additional jaw fragments, broken p4 and milk dentition listed by Henshaw (1942: 110); LACM ( CIT) 15978, left partial ramus with m1 broken– m2, m3 alveolus.

Fox Hill, UCMP locality V6021 (early Clarendonian), Cedar Mountain, Mineral County, Nevada; UCMP 58666, right partial ramus with p4 alveolus–m1, m2 alveolus.

Avawatz Mountains (early Clarendonian), San Bernardino County, California: LACM ( CIT) 2308, right partial maxilla with P1–P4, listed by Henshaw (1939: 17, pl. 2, fig. 2, 2a).

UCMP locality 2731, lower part of the Dove Spring Formation (early Clarendonian) Mohave Desert, Kern County, California: UCMP 22319, partial mandible with i1–p2, p3 broken, p4, m1–m2 broken, m3, listed and figured by Merriam (1919: 533, fig. 138a–b). Martha Pocket, UCMP locality V6731, upper part of the Dove Spring Formation (latest Clarendonian), Kern County, California: UCMP 77703, skull with C broken, P1, P2 alveolus, P3 (broken)–M2, and mandible with c–m3 (fig. 16). LACM locality 3580, upper part of the Dove Spring Formation (about 200 m below UCMP 77703, D.P. Whistler, personal commun., 1981; late Clarendonian), Kern County, California: LACM 122324*, fragmentary mandible with m2 and alveoli; LACM 122325*, left ramus p1 alveolus, p1–p2, p3 alveolus, p4–m2; LACM 122326*, left m2.

Distribution: Late Barstovian of Nebraska, Kansas, New Mexico, and Nevada, earliest Clarendonian of Nebraska, early to late Clarendonian of California and Nevada.

Revised Diagnosis: Distinguished from L. leidyi by its significantly larger size (95% confidence interval for first lower molars of these taxa nearly separated;fig. 7), m2 shorter relative to m1 (fig. 7) with enlarged anterolabial cingulum and large metaconid, cranium lacks postparietal foramina, shows reduced cerebellar exposure, and nasals do not extend posterior to maxillary-frontal suture. Distinguished from L. tejonensis in longer muzzle and more widely spaced and anteroposteriorly longer premolars with stronger accessory cusps. L. vafer differs from L. matthewi in significantly smaller size, with no overlap of m1 95% confidence intervals (fig. 7) nasals do not extend posterior to maxillary-frontal suture, M2 lacks postprotocrista, m1 lacks hypoconulid shelf, and entoconid not enlarged.

Description and Comparison: The skull of L. vafer is based on hitherto undescribed specimens, including two partial skulls, UNSM 25717 and 25718 (fig. 14A–D), from the Valentine Formation in Nebraska, a wellpreserved skull and jaws ( UCMP 77703, fig. 16) from the upper part of the Dove Spring Formation in California, and two partial skulls (F:AM 62763, fig. 15A–D, and F: AM 62845) from the Pojoaque Member of the Tesuque Formation in New Mexico.

Except for the narrower muzzle, more laterally expanded cranium, and the more robust zygomatic arch, the skull of L. vafer for the most part resembles that of L. mollis and L. gregorii in size and proportions (see fig. 3). The premaxillary and frontal processes are widely separated, and the frontals are unelevated with a slight depression on the dorsal surface of the postorbital process indicating the lack of a frontal sinus as in Vulpes . Also like Vulpes species , the nasals are short in L. vafer , terminating anterior to the frontal-maxillary suture. From the prominent postorbital processes the weak frontal crests extend posteriorly and join near the frontoparietal suture to form a low sagittal crest. Compared to earlier species of Leptocyon , the most striking features of the cranium of L. vafer are the reduced cerebellar exposure resulting from relative expansion of the neocortex and the consequent loss of the postparietal foramina. The maxillary beneath the orbit and the zygomatic process of the jugal are dorsoventrally deeper in L. vafer , and the jugal bears a stronger scar for origin of the masseter muscle than in other species of Leptocyon in which this structure is known.

Viewed ventrally, the basioccipital is relatively narrow between the inflated bullae. The medial wall of the bulla slightly underhangs the basicranial bones at the level of the basioccipital-basisphenoid suture. Compared with L. gregorii , the bulla is anteroposteriorly shorter, with the lip of the auditory meatus projecting more laterally. The tympanic bulla in L. vafer lacks the depression in the ectotympanic anterior to the auditory meatus seen in L. mollis and L. gregorii . A swelling of the posterolateral border of the entotympanic below the stylomastoid foramen is evident in L. vafer ( UCMP 77703) and in L. matthewi (F: AM 49433). A similar bulge of the entotympanic is more pronounced in V. stenognathus (F: AM 75827), which approaches the condition in V. vulpes . In L. vafer the paroccipital process is relatively larger than in earlier species of Leptocyon . It extends more ventrally with the anterior surface more concave and covering more of the posterior wall of the bulla, foreshadowing the condition in Vulpes .

Despite the widespread geographical and temporal range of L. vafer , the dentition is remarkably homogeneous in size and morphology. The coefficients of variation (appendix 3) of the total sample range mostly below 7.0 except for the length of P1 and p1. We therefore have assigned these widely separated samples to L. vafer .

The limbs of L. vafer stand morphologically between those of L. vulpinus and those of Hemphillian Vulpes stenognathus . Compared to the limbs of L. vulpinus , the distal end of the humerus is transversely narrower with a smaller entepicondylar foramen and a smaller entepicondyle (fig. 9). The radius is also less robust with the distal end narrower relative to the shaft and a smaller styloid process (fig. 9). The most striking difference is the smaller distomedial radial exostosis. The hind-limb morphology is known best from an articulated tibia, partial fibula and nearly complete pes (F:AM 62780, fig. 9G– H) from New Mexico. The length of the tibia is shorter than that of Vulpes with the length approximating that of the pes. Furthermore, the proximoanterior crest is longer relative to the length of the tibia and the proximal condyles that articulate with the femur are less anteriorly and distally extended. The fibula is less robust than that of L. vulpinus , but not as slender and compressed as in Vulpes . A functional first digit is present. It bears two phalanges and its length is about 60% of the length of metatarsal II.

Discussion: The genotypic species, Leptocyon vafer , was first described by Leidy (1858: 21) as a small species of Canis as were most living foxes at that time. Leidy recognized its foxlike features and remarked that they did not differ from those of the red fox. As early as 1897, Trouessart listed this taxon as Vulpes vafer in his catalogue of mammals, but Matthew (1909: 115) followed Leidy and listed this species as Canis vafer in his faunal lists of the Tertiary Mammalia of the West. Later Matthew (1918: 189) recognized that the morphology of the lower jaw and dentition differed from both Canis and Vulpes , and he designated C. vafer the type species of a new genus, Leptocyon . Because of the lack of perception of diagnostic dental features, uncertainty persisted regarding the generic allocation of this species. Merriam (1919: 533) followed Leidy and referred a jaw from the Dove Spring (Ricardo) Formation in California to ‘‘ Canis ? vafer ’’ and commented that it is ‘‘not unlike Canis ? vafer Leidy of the Fort Niobrara Formation.’’ Stirton and McGrew (1935: 129) listed this taxon as Vulpes vafer in their list of the Niobrara River Fauna. A fragmentary maxilla from the Avawatz Mountains of California listed as ‘‘Canid indet.’’ By Henshaw (1939: 17) was said to possess features that resemble ‘‘fairly closely those of Vulpes vafer (Leidy) .’’ Three year later, however, Henshaw (1942: 110) recognized Matthew’s genus, Leptocyon , and referred two jaws from the Tonopah Local Fauna of Nevada to L. vafer . Macdonald (1948: 55) reverted to the use of Vulpes in referring two partial jaws from the Black Hawk Ranch Local Fauna of California to Vulpes vafer .

Thus, L. vafer was buffeted among Canis , Vulpes and Leptocyon for over a century. Uncertainty about the generic allocation of this species continued until Webb (1969: 39) effectively diagnosed this taxon and described the dental characters that distinguish Leptocyon from Vulpes . The additional evidence described herein has enabled us to amplify the description of L. vafer and to revise and strengthen the diagnosis for both the genus, Leptocyon , and the species, L. vafer .