Xenocyon Kretzoi, 1938

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 : 150-152

Xenocyon Kretzoi, 1938

Sinicuon Kretzoi, 1941: 118 .

Canis (Xenocyon) Rook, 1994: 71 .

Type Species: X. lycaonoides Kretzoi, 1938 .

North American Species: X. texanus (Troxell), 1915 , and material referred here to X. lycaonoides Kretzoi, 1938 .

Distribution of North American Species: Late Irvingtonian of Texas; Olyorian (medial Pleistocene) of Alaska and Yukon.

Diagnosis (follows Schütt, 1974, and Sotnikova, 2001): Canids of large size, comparable to C. lupus ; horizontal ramus deep and robust; coronoid process low relative to length; cheek toothrow straight, lacking inward inflection at premolar-molar junction seen in C. lupus ; canines with short crowns; M1 with weakly developed labial and lingual cinguli, hypocone small, conules weakly developed; M2 not markedly reduced relative to M1, metaconule absent, postprotocrista present; lower premolar row lacks diastemata; p2 and p3 without posterior cusp; p4 with posterior cusp; posterior cingulum of p3 lies below base of crown of p4; p4 with second posterior cusp anterior to cingulum; tip of p4 lies at or above tip of m1 paraconid; m1 metaconid greatly reduced, entoconid represented by a low crest or absent, yet hypoconid often retains trace of connecting cristid, hypoconid nearly centrally positioned on talonid; m2 not markedly reduced relative to m1, metaconid greatly reduced but present, hypoconid present and labially placed on talonid, entoconid not differentiated from lingual talonid crest; anterolabial cingulum weak or absent; m3 present and bicuspid.

Discussion: In describing the fauna of the medial Pleistocene fissure fills at Gombaszög (Gombasek), Hungary, Kretzoi (1938: 132) designated the right M1 of a large canid the holotype of Xenocyon lycaonoides , n. gen., n. sp., and, in the same work, but on page 128, he designated a left ramal fragment with a p4 and trigonid of m1 ‘‘ Canis ’’ gigas , n. sp. In a review of the fauna based on later collections, Kretzoi (1941: 112) recognized that these fragments belong to a single taxon and took the name with page precedence, making ‘‘ C. ’’ gigas the genotypic species. He pointed out the dental similarities to Cuon and Lycaon (the most striking are related to hypercarnivory), but noted that Xenocyon gigas was significantly larger and retained m3. The latter feature was indicated by a right ramal fragment with the m3 alveolus ( Kretzoi, 1941: pl. V, fig.1). A year later, Kretzoi (1942) realized that Canus gigas was a preoccupied name and renamed the genotyp- ic species C. spelaeoides . When Musil (1972) described the Xenocyon sample from Stránska Skála he used the name X. spelaeoides Kretzoi, 1942 , as the material was clearly referable to that Gombaszög species. Furthermore, as the genus Xenocyon was based on X. lycaonoides Kretzoi, 1938 , recognition that C. gigas , described in the same paper, was the same taxon is no grounds for submersion of lycaonoides and thus the homonomy of C. gigas is not relevant. For this reason we follow later workers (beginning with Schütt, 1973) in using Xenocyon lycaonoides as the name for the genotypic species.

In a revision of the Lycaoninae (Gray), 1868 (included in Caninae by McKenna and Bell, 1997), Kretzoi (1941) erected Sinucuon for S. peii , n. sp. based on ‘‘ Cuon , sp. nov. ’’ of Pei (1939) from Choukoutien locality 18. He was apparently unaware that this taxon had already been described from locality 18 as Cuon dubius by Teilhard de Chardin in 1940. Later, Schütt (1974) referred C. dubius to Xenocyon , thus extending the geological and geographic range of the genus into the late Pliocene of China. Thenius (1954: fig. 33b) proposed Cuon dubius stehlini based on isolated teeth from Rosiéres (Cher), France, in which the presence or absence of m3 could not be seen. Schütt (1973) held this taxon as a synonym of X. lycaonoides . To further confound the confusion between Xenocyon and Cuon , there is a large true Cuon , C. alpinus priscus Thenius, 1954 , that occurs with X. lycaonoides at Mosbach II (Weisbaden), Germany ( Schütt, 1973).

In 1994 Rook, following a suggestion of Torre (1967), reduced Xenocyon to a subgenus of Canis and relegated the large early Pleistocene taxa as C. falconeri Forsyth- Major (1877) from the Upper Valdarno deposits in Tuscany, Italy; C. antonii Zdansky, 1924 , from Honan, China; and C. africanus Pohle, 1928 , from Olduvai Gorge, Bed II, Tanzania, to a supraspecific group (i.e., a clade) termed Canis (Xenocyon) ex gr. falconeri , whose constituent taxa were ‘‘semispecies … representing the extremes of the geographic range of the taxon’’ ( Rook, 1994: 72). The diagnosis of this group differed from that of Xenocyon sensu stricto by the primitive states of most of the dental features detailed above, although the metaconids of m1 and m2 were said to be relatively reduced, the upper molars had a marked tendency toward brachyodonty, and the neural cranium was relatively short. Based on the evidence presented, a good case can be made for the phyletic union of the named taxa, but our phyletic results show a more divergent relationship (see below and fig. 65).

Present evidence indicates that Xenocyon is represented in the late Pliocene only by X. dubius , a taxon so far unrecognized beyond its type site near Beijing. Xenocyon lycaonoides , the genotypic species, has a wide geographic range from Europe across Asia into northern North America in the medial Pleistocene. An endemic form, X. texanus (Troxell), 1915 , occurred at the same time in the New World middle latitudes.