Canis thöoides, 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 : 119-121

Canis thöoides , new species Figure 40, 45A–C, 52; appendices 3, 4

Type: F:AM 63101, right (fig. 45B–C) and left rami with c–m3, maxillary fragments and isolated teeth including right (fig. 45A) and left C–M2 (P1 broken), partial scapula, right humerus and left partial humerus, left radius and articulated incomplete ulna, right incom- plete radius and ulna, left articulated metacarpals I–V and most phalanges, both incomplete tibiae, partial fibula, calcaneum, astragalus, and articulated metatarsals II–V with most phalanges. Flat Tire Fauna, Dry Mountain locality (late Blancan), 32 km southeast of Safford on the east side of the San Simon Valley, Graham County, Arizona.

Etymology: Greek: thos, jackal; oides, similar in form.

Referred Material: Saint David locality, Saint David Formation (late Blancan), San Pedro Valley, east of Saint David, Cochise County, Arizona: F:AM 63092, right partial ramus with p3–m2.

Distribution: Known only from the late Blancan of Arizona.

Diagnosis: Canis thöoides differs from C. lepophagus and resembles more derived species of Canis in its wide premolars, especially p4 with its posterolingual cingular shelf; like C. aureus , it differs from C. ferox in possessing primitive states of derived features of that and other crown group species. The P4 protocone extends anterior to the paracone; I3 not markedly enlarged, with weak median cingulum; p4 principal cusp exceeds m1 paraconid in height; m1 anterior face of paraconid vertical or nearly so; m3 bicuspid. The isolation of all premolars by diastemata seems an autapomorphy in C. thöoides .

Description and Comparison: In the course of this work we found three canid taxa of late Blancan to early Rancholabrean age that appear to be morphologically similar to the Asian golden jackal, Canis aureus . Two of these taxa are known from the remains of single individuals, but the third, and oldest, C. thöoides , although known from only two individuals, is better represented dentally and skeletally.

As indicated in the diagnosis, the dentition of C. thöoides (fig. 45A–C) differs little in size or morphology from C. aureus , particularly with regard to Asian populations. The only consistent differences are: in C. thöoides P2– P3 and p2–p4 are wider and higher crowned than in C. aureus . In comparison with their length, the premolars of C. thöoides are separated by prominent diastemata, with p2 often isolated by longer diastemata; also, the protocone of P4 lies anterior to anterior face of paracone. These are mostly primitive

sides). I. Ramus, occlusal view. J–O. Canis aureus aureus , skull and mandible, AMNH(M) 81041, Recent, Abyssinia. J. Occlusal view. K. Palatal

. L. Dorsal view. M. Lateral view. N. Ramus, lateral view. O. Ramus, occlusal view. The longer (upper) scale is for A, B, E, G, I, J, and O, and the shorter (lower) one is for the rest.

characters. Even the isolation of the premolars by longer diastemata is present in C. latrans and in individuals of E. davisi in which it is related to a longer muzzle as in C. thöoides . Ontogenetically older individuals of C. aureus also occasionally show this feature.

The P4 of C. thöoides is stout (width across the paracone is approximated by that across the metacone) and the relatively small protocone lies anteriorly. The cingulum is confined to the labial and lingual bases of the metacone. A paraconule is not differentiated in the M1 as it is in C. aureus , nor is the lingual cingulum continuous across the protocone as in individuals of C. aureus . Likewise, in C. aureus the paracone is noticeably larger than the metacone of M1 but not as markedly so as in the coyotes and wolves. The labial cingulum is continuous across the face of the tooth as in C. aureus , and the parastyle is no larger in C. thöoides than in the golden jackal. The M2 is similar to that in C. aureus in size and shape relative to M1. There is a broad labial cingular shelf in both taxa. As in C. aureus , the postprotocrista does not quite reach the posterior border of the tooth where a slight swelling represents the metaconule.

The p3–p4 have posterior cusps, and the p4 of F:AM 63092 shows a tiny second posterior cusplet lacking on the type, but present in C. aureus . There is a marked widening of the p4 posteriorly due to the development of a posterolingual cingular shelf. The m1 is robust, with its talonid as wide or wider than the trigonid. Cristids from the hypoconid and entoconid join these cusps although they are weakly expressed in F:AM 63092. The entoconid lies slightly behind the hypoconid and there is a hypoconulid shelf developed posterior to the transverse cristids. The anterolabial cingulum on m2 is well developed and passes posteriorly across the labial face of the protoconid in F:AM 63092, but not in the type. The cingulum is confined to the anterolabial face of the protoconid of m 2 in C. aureus . A small paraconid is present in F:AM 63092, but it seems lacking in the type. Similar variation is present in C. aureus . The length of the talonid is less than 90% that of the trigonid, and the hypoconid, but not an entoconid, is differentiated from the ridge surrounding the talonid basin. The m3 is oval to nearly circular in occlusal outline and bears two trigonid cusps set opposite or slightly oblique to one another as in C. aureus .

The partial skeleton of the holotype gives information on the forelimb elements of C. thöoides in comparison with C. aureus . The proportions of the radius to humerus show that C. thöoides has a markedly shorter radius relative to the length of the humerus than in C. aureus or C. latrans , whereas the length of radius to metacarpal III is comparable in all these taxa. The length of the radius with respect to the tibia (88%) lies within the values for the golden jackal (87%– 93%) and just below that for coyotes (89%– 92%), implying a derived long distal forelimb in C. thöoides yet not reaching modern levels in its relationship with the proximal forelimb (fig. 52). This is a primitive feature only exceeded by the longer forelimbs of coyotes and wolves.

Discussion: It is interesting to see a jackallike form as a product of the Blancan radiation of Canis species in North America. This clade appears to continue into the early and medial Pleistocene with the poorly known C. feneus and C. cedazoensis . Although jackals are today confined to southern Eurasia and Africa, they are rare in the fossil record ( Turner, 1990). The recent announcement of the discovery in Morocco ( Geraads, 1997) of a taxon of late Pliocene age (2.5 Ma) thought to be close to C. aureus seems on the other hand to be a primitive form closer in size and morphology to Eucyon davisi previously recorded in deposits of similar age in China ( Tedford and Qiu, 1996) and more recently in Macedonia ( Koufos, 1997). The reference of fragmentary jackal material from the early Pleistocene site at l’Ain Boucherit, Morocco, to C. aureus (as C. anthus primaevus ) by Arambourg (1979) may be the oldest African record of this taxon. Jackals are apparently unrecognized in the Pliocene or early–medial Pleistocene of Eurasia.