Metalopex Tedford and Wang, 2008

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 : 58-66

Metalopex Tedford and Wang, 2008

Type Species: Metalopex merriami Tedford and Wang, 2008 .

Included Species: M. macconnelli , new species, and M. bakeri , new species.

Distribution: Late Clarendonian of Arizona and California, late Clarendonian or early Hemphillian of Oregon and New Mexico, early Hemphillian of Idaho, Nevada, Oregon, and Nebraska, and medial Hemphillian of Texas.

Etymology: Greek: meta, near and alopex, fox.

Diagnosis: Derived features that distinguish Metalopex from Vulpes are: mastoid process large; M1 and M2 more quadrate in shape, anteroposteriorly long relative to width; M2 lacks postprotocristid; p2 isolated by longer diastemata; m1 and m2 have protostylids; m2 large relative to m1, more posteriorly extended anterolabial cingulum, and talonid longer relative to trigonid; m3 uniquely elongate, trigonid longer than talonid, that is, relatively large paraconid shelf, protoconid, and metaconid situated more posteriorly.

Primitive characters retained by Metalopex include: marked depression on frontals adjacent to postorbital process; basioccipital wide; bulla small; strong medial and lateral cusplets on I2 and medial cusplet on I3; M2 metaconule present despite reduction and loss of connecting postprotocrista; m1 talonid lacks transverse crest between entoconid and hypoconid and also lacks hypoconulid; and m2 with paraconid or strong paracristid.

Discussion: Although the morphological features of Metalopex are most typically developed in the type (F: AM 49282) of the genotypic species, M. merriami , the smaller species, M. macconnelli , which is intermediate in size and cranial proportions (fig. 27) between its contemporary Leptocyon vafer and Vulpes stenognathus , also clearly exhibits these characters. Metalopex differs principally from both Vulpes and Urocyon in its unique M2, which lacks a postprotocrista but retains the metaconule; in retaining the primitive form of the upper incisors in which I3 still has a medial cusp; in its relatively derived enlargement of the mastoid process (compare posterior views of the crania of Leptocyon vafer , fig. 61A, with Metalopex macconnelli , fig. 61B); and in the uniquely enlarged m3, which retains the primitive trigonid and talonid.

Metalopex macconnelli , new species Figures 7, 24A–S, 26A–E, 27, 28, 61B; appendices 2, 3

Type: LACM 55237, crushed skull (fig. 24A–C) with I1–M2 and both ramal fragments including p3–p4 broken, m1 incomplete alveolus, isolated m2 trigonid (fig. 24D), and a broken isolated lower canine from Red Rock Canyon, LACM locality 3552, upper part of the Dove Spring Formation (late Clarendonian), Kern County, California.

Etymology: Named in honor of J. Mac- Connell, of Diamond Springs, who, with his family, collected the type and generously donated it and many other fine specimens to the Los Angeles County Museum.

Referred Material: LACM 55219 , left ramus (fig. 24E–F) with c broken–m3 (p2 broken) from Red Rock Canyon, LACM locality 3552, Kern County, California, upper part of the Dove Springs Formation, 200 m below the occurrence of the type (late Clarendonian). LACM 122323 , right and left maxillary fragments, P2–P4, M1–M2, LACM locality 3580, 100 m above the occurrence of the type in rocks of earliest Hemphillian age, Kern County , California. UCMP 33707 , left partial ramus with c–m1 alveoli, m2, and m3 alveolus (figured by Macdonald, 1948: fig. 2; fig. 28A–B of this paper) .

Walnut Grove Basin, Milk Creek Formation (late Clarendonian), Yavapai County, Arizona: UA 361-49, skull (fig. 24K–M) with C broken–M2; UA 359-49, mandible with i1– i2 both broken, and i3–m3 (c, p2, and p4 all broken, possibly same individual as UA 361- 49, fig. 24P–Q); UA 328-49, anterior part of skull with C–M2 and mandible with i1–m2 (p4 and m2 broken); UA 349-49, right and left partial maxillae with P2 alveolus–M2; UA 434-49, left maxilla with C–P3 alveoli and P4–M2 (M1 broken); UA 329-49, right ramal fragment with p4, and m1 broken; UA 408-49, detached canine, p1, p2, p3, and right and left m1s; UA 358-49*, detached p4, fragment of p4, proximal part of radius and ulna, distal fragment of tibia, cuboid, astragulus, and right and left calcanea, Quarry 3. UA 37-49, crushed partial skull with I1–M2, Quarry 1.

From the Milk Creek area, Milk Creek Formation (Clarendonian), Yavapai County, Arizona: F:AM 63065, left partial maxilla with P3 broken–M2 (P4 broken); F:AM 63066, right and left partial rami with p2 root, p3 broken–m3, Manzanita Quarry; F:AM 63067*, right and left partial rami with c broken–p4 (p2, m1, and m2 broken), Cliff Prospect.

Late Clarendonian or early Hemphillian (C.A. Repenning, personal commun.), Malheur County, Oregon: NMNH 23883, right partial ramus (fig. 24R–S) with p4–m3, from Saddle Butte, USGS locality M1099; and NMNH 184113, left anterior fragment of skull with I1–M2 and associated mandible (fig. 24G–J) with i1–m3 from Sand Spring, USGS locality M1419.

Distribution: Late Clarendonian and early Hemphillian of California, late Clarendonian of Arizona, and late Clarendonian or early Hemphillian of Oregon.

Diagnosis: Differs from M. merriami in smaller size; lyrate temporal crests that join posterior to frontoparietal suture in short, weak sagittal crest; occiput narrower with lambdoidal crests subdued; bullae larger relative to size of skull; I2 with weaker lateral cusplet and weaker lingual cingulum; dentition lower crowned; M1–M2 less quadrate with stronger labial cingulum on paracone of M1; M2 smaller relative to M1; m1 slenderer with less oblique paraconid, and narrow talonid; and m3 trigonid shorter relative to length of talonid.

Description and Comparison: The morphological features of the type skull ( LACM 55237) and referred skull ( UA 361-49) of M. macconnelli , for the most part, recall those of Leptocyon , but the relative enlargement of the mastoid process of the periotic is like that of the genotype, Metalopex merriami . The skull characters cited in the diagnosis that distinguish this species from M. merriami are in turn similar to those L. vafer . Likewise, the mandible is elongate and slender and the angular process (lacking only the tip in the right ramus of NMNH 189113) bears the pterygoid and masseter scars of primitive configuration ( Tedford et al., 1995: fig. 5A, ‘‘ type A’’ of Gaspard, 1964). The incisors of M. macconnelli are simple and possess the basic features of Leptocyon . In both taxa, the I2 has a minute medial and lateral accessory cusp on the crown and a faint lingual cingulum. The third upper incisor is about one-third larger than I2 with a more promiment medial accessory cusp and a stronger lingual cingulum. The incisors of the type of M. merriami are similar to those of M. macconnelli , but the accessory cusps and cingula are stronger in the isolated premaxilla referred to M. merriami from Nebraska ( UNSM 26115), and the I3 is more compressed.

The premolars in M. macconnelli are moderately long but taller crowned relative to their length than are those of L. vafer , but they are shorter crowned than in M. merriami . The premolars are slender and widely spaced, with the p2 being the most isolated by diastemata. The P4 is slender, has a welldeveloped protocone, and is indistinguishable from that of Leptocyon .

In M. macconnelli , it is principally the molars above and below that differ from L. vafer and Vulpes stenognathus and possess features in common with Metalopex merriami . Compared to a skull of L. vafer ( UCMP 77703, fig. 16), from about 100 m above the type of M. macconnelli in the upper part of the Dove Springs Formation of California, M. macconnelli has relatively larger molars with the anteroposterior dimensions of M1 and M2 longer relative to their width. In M. macconnelli the lingual cingulum on the M1 and M2 is weaker, especially where it begins at the protocone. The shape of the M1 and M2 is intermediate between that of L. vafer and the more quadrate molars of M. merriami . The M2 is markedly larger and more quadrate than those of L. vafer and V. stenognathus , and it retains the metaconule although this cusp is not always linked to the protocone by a postprotocristid.

The m1 of M. macconnelli closely resembles that of L. vafer ( UCMP 77703) from the upper part of the Ricardo Formation of California. Its trigonid is moderately long as in Leptocyon and slightly longer with a less oblique paraconid than that of M. merriami . It differs mainly from L. vafer in its longer talonid that occludes with the more quadrate M1.

The isolated broken anterior half of m2 of the type ( LACM 55237) differs from L. vafer in that the trigonid is relatively long with a distinct paraconid as in M. merriami . A distinct paraconid is present in four of the six m2s listed here, but this is a variable character as shown in two jaws ( NMNH 184113 and UA 328-49) in which only a paracristid is present as in L. vafer . The above features of the m2 of the type are confirmed by the additional referred mandibular rami. These rami also show the nature of the talonid of m2 which, like that of the genotypic species, show marked elongation, although this is subject to some variation, being especially marked in the Oregon material as further noted below.

The m3 of M. macconnelli are markedly larger than those of L. vafer and V. stenognathus , and it is relatively larger and more elongate than that of Leptocyon . A minute paracristid may be present, and the subequal protoconid and metaconid are larger than in L. vafer . Moreover, they are situated more posteriorly, making the trigonid longer than the talonid. This unusually large m3 and its long trigonid are characteristic of Metalopex .

Macdonald (1948: 56, fig. 2) figured a mandibular fragment from Black Hawk Ranch ( UCMP 33707) with only an m2 and alveoli for the other cheek teeth and concluded that it was ‘‘possibly related to Urocyon .’’ Macdonald listed three additional m2s, which are included in our referred material. He also listed a badly worn upper molar ( UCMP 33709) that is not included herein because its extreme wear prevents positive assignment to a taxon. We have recognized additional material from the Black Hawk Ranch Quarry that includes most of the upper and lower molars. These specimens differ from the other materials assigned to this taxon in some ways that deserve additional description and analysis.

The mandibular ramus is no larger than that of L. vafer , but the horizontal ramus is deeper below the p1 and comparable to that of other M. macconnelli . Judging by the length of the alveoli, the premolars were shorter than most individuals of M. macconnelli . A short diastema isolates p2 from p1, and a still longer diastema (4.5 mm) separates p2 from p3.

The m 1 in the Black Hawk Ranch sample shows variable development of the protostylid, perhaps more characteristic of Urocyon than the much weaker protostylids of the other samples of M. macconnelli . The m1 talonid has a distinct entoconulid and the entoconid is smaller and lower crowned than the hypoconid. The m2 is elongate with a relatively long trigonid and a small but distinct paraconid. A well-developed anterolabial cingulum extends posteriorly only to the protoconid where a weak prostylid is present. This is a derived feature that is shared with Urocyon . The talonid is elongate with a well-developed entoconid and hypoconid.

The upper dentition referred to M. macconnelli from Black Hawk Ranch includes three P4s, two M1s, and an M2. The P4 ( UCMP 112188) is robust with a strong anteriorly directed protocone. The parastyle is not present on the P4 from Black Hawk Ranch, and because of the abrasion of the enamel, it is also uncertain if a labial cingulum was present. The M1 bears a strong lingual cingulum that begins at the base of the paracone and ends posteriorly labial to the metaconule at the base of the metacone. The M1 has a well-developed metaconule connected by the protocrista to the protocone; however, this connection is not present on the M2, where the small metaconule is isolated from the protocone as typical of Metalopex rather than Urocyon .

Thus, the Black Hawk Ranch sample diverges slightly from others of M. macconnelli in the development of the m1–m2 protostylid in a manner foreshadowing the more consistent occurrence of this structure in Urocyon . The morphology of one partial ramus ( NMNH 23883, fig. 24R–S) also differs from the other jaws of M. macconnelli and tends to be intermediate between the latter and the more derived specimens of M. merriami .

Although the p4 and m1 of NMNH 23883 compares favorably with the other materials referred to M. macconnelli , the last two molars are more like those of M. merriami . The m2 ( NMNH 23883) is elongate with a distinct paraconid, a labial cingulum that extends to the hypoconid, and it possesses an especially long talonid with a minute entostylid as in M. merriami . Its m3 is typically elongate with a long trigonid and a welldeveloped subequal protoconid and metaconid. We interpret these features as variation within a later occurring population of M. macconnelli in view of evidence for considerable variation shown by materials of both species of the genus. As discussed under M. merriami , the small samples available for the genus seem to show chronoclinally distributed size and morphological variation that suggest an anagenetic trend that is here somewhat arbitrarily segmented taxonomically.

Metalopex merriami Tedford and Wang, 2008 Figures 7, 25A–I, 28; appendices 2, 3

Vulpes sp. : Becker and McDonald, 1998: 33. Tephrocyon , near kelloggi: Merriam, 1911: 238.

Type: F:AM 49282, partial skull with I3 alveolus–M2, detached premaxillary fragament with I1–I2, and left partial ramus with c alveolus–m3 (p1 alveolus and m1 broken, fig. 25A–D, F–G) from 3 miles north of Line Quarry, just north of the Oregon – Nevada state line, Thousand Creek Formation (early Hemphillian), Harney County, Oregon.

Referred Material: From near the type locality, Line Quarry, Thousand Creek Formation (early Hemphillian), Humboldt County, Nevada: F:AM 61016, left partial ramus with m1 and m2–m3 both broken (fig. 25E). From UCMP locality 1103, Thousand Creek Formation, Humboldt County, Nevada, UCMP 12542, right m2 ( Merriam, 1911: fig. 7).

From Mitchell Road, UCMP locality V4825, Rattlesnake Formation (early Hemphillian), Wheeler County, Oregon: UCMP 41084, left isolated M1 and M2.

From Star Valley, IMNH locality 67001, sediments interbedded with Banbury Basalt (early Hemphillian), Owyhee County, Idaho: IMNH 24584, right partial ramus with p4– m2; IMNH 27886*, left partial ramus with c, p1–p4, and m1.

From Kern River, LACM ( CIT) locality 49, Kern River Formation (early Hemphillian), Kern County, California: LACM 55217, left partial ramus with c (alveolus)– m2 (p1 alveolus, p2 broken, and p3–p4 alveoli).

From Gabaldon Badlands, 4 miles south of Rio Puerco station (late Clarendonian or early Hemphillian), Valencia County, New Mexico: F:AM 107607*, two fragments of right ramus with c–p2 all alveoli, p3, p4 root, and m1–m2 both broken ( Lozinsky and Tedford, 1991: 25, fig. 18D).

UNSM, locality Ft. 48 (early Hemphillian), Ash Hollow Formation, Frontier County, Nebraska: UNSM 521-47*, left partial ramus with c alveolus, p1, p2–p3 both broken, p4 root, and m1–m3 alveoli; UNSM 419-47, right maxillary fragment with M1– M2; UNSM 522-47, left maxillary fragment with P2–P3, protocone root of P4, Ft. 48; UNSM 26098, right ramus with c–alveolus, p1–m1 (p2 broken), m2 broken, and m3 alveolus (fig. 25H–I); UNSM 26135, left premaxilla with I1–I3, right and left ramal fragments with c alveolus–p4; UNSM 26136, left m1, Ft. 49. UNSM (unnumbered) right and left rami, right c (alveolus), p1–p3, anterior half p4, left i1–i3, c, p1 alveolus, p2– p3 broken, Ft. 40.

Distribution: Latest Clarendonian or early Hemphillian of New Mexico, and early Hemphillian of California, Idaho, Nevada, Oregon, and Nebraska.

Diagnosis: Differs from M. macconnelli in larger size, wider muzzle, temporal crests joining anterior to frontal parietal suture to form strong sagittal crest; occiput broader with stronger lambdoidal crests; bullae small- er relative to size of skull; I2 with stronger lateral cusplet and stronger lingual cingulum; I3 with stronger medial cusplet, larger lingual shelf, and more laterally compressed; cheek tooth dentition taller crowned; M1 and M2 more quadrate with weaker labial cingulum on paracone of M1; m1 more robust with paraconid more oblique, wider talonid with posterior cingulum extremely weak or absent; m2 larger relative to m1; and m3 trigonid longer relative to length of talonid.

Description and Comparison: In the type skull (F: AM 49282) the premaxilla, maxilla, nasals, and frontals are incomplete and the basicranial area is crushed and broken. The skull is elongate, larger than V. stenognathus , and approximates the size of Eucyon davisi . Unlike Vulpes , the contour of the maxillary surface above P1–P3 is convex as in E. davisi . Furthermore, the skull differs from that of V. stenognathus and is similar to Eucyon davisi in the wider and more arched palate and the greater dorsoventral height of the maxilla. Unfortunately, the frontals are broken, thus obscuring the maxillary-frontal suture, but the remnants do not contradict an extension of the suture beyond the posterior end of the nasals. A fragment of the frontal with the postorbital process shows the primitive frontal depression adjacent to the process as in Vulpes . Moreover, the frontal fragment also reveals that M. merriami lacks the frontal sinus seen in Eucyon . Enough of the frontals are present to show that the temporal crests join anterior to the parietal suture to form a moderately low sagittal crest similar to that in both V. stenognathus and E. davisi . In M. merriami , the braincase is elongate and expanded. It is markedely wider anterior to the frontoparietal suture than in V. stenognathus and E. davisi . The supraoccipital shield is broad, with the inion broader than in V. stenognathus and similar to that of E. davisi . Unlike Vulpes , the lambdoidal crests are strong and similar to those of E. davisi . The foramen magnum and occipital condyles are larger than in V. stenognathus and Eucyon davisi , and the mastoid process is knoblike and enlarged as in the Canini . Although the basioccipital area is badly broken, it appears relatively wider than in both V. stenognathus and E. davisi , and the broken tympanic bullae show that the bullae are small relative to the size of the skull.

A premaxillary fragment ( UNSM 26135) has an unworn I2 and I3. The I2 has a welldeveloped medial and lateral cusplet and the I3 has a well-developed medial cusplet but no lateral cusplet. Both incisors have a lingual cingulum and there is a broad lingual shelf on I3. The complexity of the upper incisors exceeds that of M. macconnelli , E. davisi , Leptocyon vafer , and V. vulpes , but the I3 is not enlarged as in the Canini . Compared to both V. stenognathus and E. davisi , the P1–P3 are smaller relative to the length of the carnassial, more widely spaced, slenderer, and anteroposteriorly shorter and taller crowned. They also lack accessory cusps, but P3 may have a cusp on the posterior cingulum. Morphologically, the P4 closely resembles that of V. stenognathus and E. davisi , with the anterior border slightly notched due to the projection of the anterobuccal corner and the strong anteriorly directed protocone. The P4, however, is smaller relative to the molars than in both of the above and is more slender than that of E. davisi . Unlike V. stenognathus and E. davisi , the M1 and M 2 in M. merriami are quadrate in shape, being anteroposteriorly long relative to their width. They are relatively low-crowned, the labial border is strongly indented between the paracone and metacone, there is a prominent labial cingulum, and the small parastyle retains its connection with the preparacrista. The protocone of M1 is relatively large, and a postprotocrista extends to a well-developed metaconule. The hypocone is a long and ridgelike swelling of the posterolingual cingulum, with the cingulum ending posteriorly at or just beyond the metaconule and extending anteriorly to join the anterolingual cingulum across the protocone to the base of the paracone. The M2 of M. merriami is even more quadrate than M1 and, like that of M. macconnelli , the metaconule is present but there is no postprotocrista connecting it with the protocone. The lingual cingulum extends posteriorly just to the metaconule and anteriorly across the protocone to the paracone.

In M. merriami the p2–p4 are slender and tall-crowned for their length, and only p4 consistently possesses a posterior cusp. The p2 is isolated from adjacent premolars by large diastemata as in M. macconnelli and species of the Urocyon group. The m1 is relatively short and robust with the trigonid shorter relative to the length of the tooth than that of V. stenognathus and E. davisi . Furthermore, the paraconid is more oblique and the metaconid is stronger and higher relative to the height of the protoconid than in either of these taxa. There is a weak protostylid on m1. The m1 talonid is broad with a relatively low and nearly subequal entoconid and hypoconid. These features of the m1 are accentuated in M. bakeri , the youngest member of the Metalopex clade. Allowing for wear, the hypoconid is still smaller and lower crowned than that of both V. stenognathus and E. davisi . A welldeveloped anterolabial cingulum extends posteriorly across the protoconid and ends on the anterior face of the hypoconid. The m2 trigonid is elongate with a paraconid that is stronger than that of V. stenognathus , with the larger metaconid situated slightly posterior to the protoconid. Compared to both V. stenognathus and E. davisi , the m2 talonid is relatively longer and wider. In M. merriami the m3 is also larger and more elongate than that of V. stenognathus and E. davisi . Moreover, the protoconid and metaconid are distinct subequal cusps that are situated more posteriorly than those of V. stenognathus or E. davisi , and the trigonid is longer than the talonid.

Discussion: As in the case of M. macconnelli , there is considerable variation in size and morphology within and between samples of M. merriami from different localities. The fragmentary materials from the Ogallala Group of Frontier County, Nebraska, for example, pertain to four individuals, two of which ( UNSM 26098 and 26135) can be usefully measured and are included in appendix 3. The measured specimens are at the extremes of size variation in the dimensions of the lower dentition. The additional materials from the same locality fit in between the measured values, indicating nearly continuous variation. The larger end of the range clearly overlaps the holotype of M. merriami ( UNSM 521-47 includes alveoli of m1–m3 and these are the size of F: AM 49282). We therefore have referred this material to M. merriami despite the near overlap in dimensions of the smallest individuals with M. macconnelli and morphological overlap with the more derived M. macconnelli specimen (i.e., NMNH 23883).

Except for the Black Hawk Ranch sample of M. macconnelli , which foreshadows aspects of the dental morphology of Urocyon , the remaining suite of material referred to the two species of Metalopex indicates considerable size and morphological intergradation, suggesting anagenetic change from the late Clarendonian to the later part of the early Hemphillian (fig. 28). This clade is extended into the medial Hemphillian by M. bakeri . What little we know of its morphology seems a clear extension of trends already present in earlier members of the clade.