Xenocyon lycaonoides 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 : 154-156

Xenocyon lycaonoides Kretzoi, 1938 Figure 58A–C; appendix 3

‘‘ Canis ’’ gigas Kretzoi, 1938: 128 .

Xenocyon lycaonoides Kretzoi, 1938: 132 .

Xenocyon gigas: Kretzoi, 1941: 112 .

Xenocyon spelaeoides Kretzoi, 1942: 345 , to replace C. gigas , preoccupied.

Cuon dubius stehlini Thenius, 1954: 18 .

Xenocyon spelaeoides: Musil, 1972: 85 .

Xenocyon lycaonoides: Schütt, 1973: 63 .

Cuon rosi Pons-Moya and Moya-Sola, 1978: 55 .

Cuon sp. , Harington, 1978: 61.

Cuon sp. , Youngman, 1993: 141.

Canis (Xenocyon) lycaonoides: Sotnikova, 2001: 622 .

Type: MNM FA 20 ( PV 4), unworn right M1, from site 3a, a terra rossa–filled fissure in the limestone quarried at Gombaszög, Hungary ( Kretzoi, 1938: pl. III, fig. 4).

Referred from Type Locality: MNM FA 19, fragment of a left ramus with broken p4 and trigonid of m1 (holotype of ‘‘ Canis ’’ gigas Kretzoi, 1938: 128 , pl. II, fig. 10); MNM PV 5, fragment of a right ramus, lacking ascending part, with incisor, canine and p1–p4 alveoli, m1 talonid, m2, and alveolus of m3 ( Kretzoi, 1941: pl. V, fig. 1).

Referred from North America: Cripple Creek Sump, Fox Gravels or lower Gold Hill Formation (Olyorian, approximately equivalent to late Irvingtonian, medial Pleistocene), near Fairbanks, Alaska: F:AM 67180, fragment of a right ramus with i1–i3, c, p1–p3 alveoli, p4 broken, m1 paraconid broken, m2, m3 alveolus (fig. 58A–B); and F:AM 97110, fragment of left ramus with alveolus of talonid of m1, m2, m3 alveolus, and ascending ramus.

NMC 14353, a fragment of a right ramus with posterior part of p1 alveolus, alveoli of p2–p3, crown of p4, and anterior part of m1 alveolus. This specimen was obtained from the Old Crow River site 14N, Yukon Territory, Canada (67 ° 51 9 N, 139 ° 46 9 W). Five C14 dates on mammal bone from this site range from 22 to36 Ka ( Harington, 1978), but the presence of the giant pika ( Ochotona cf. whartoni) and Olyor horse ( Equus cf. verae) and Xenocyon lycaonoides indicates the presence of an older fauna of medial Pleistocene age.

Quaternary nonglacial deposits, Wellsch Valley , New Mountain site (late Irvingtonian) about 10 km northwest of the town of Stewart Valley, Saskatchewan, Canada: NMC 17824*, left maxillary fragment with part of posterior alveolus of P4, M1 with labial and posterior borders broken away, M2 lost in life, alveolus filled with cancellous bone ; NMN 17825*, fragment of right premaxillary, alveoli for I1–I2, I3 well worn, broken anteriorly, anterior part of canine alveolus present. Reported as ‘‘ Borophagus diversidens ’’ by C.S. Churcher in Barendregt et al. (1991) and in previous contributions on the Wellsch Valley Fauna cited in that work .

North American Distribution: Medial Pleistocene (Olyorian) of Alaska and Yukon; late Irvingtonian of south-central Canada.

Revised Diagnosis: Rami distinguished from those of X. dubius Teilhard de Chardin, 1940 , by larger average size; premolars not as elongate, wider, and higher crowned; p2 lacks posterior cusp; second posterior cusp on p4 smaller, often closely appressed to cingulum; m2 with metaconid smaller relative to protoconid and narrower talonid.

Description and Comparison of North American Material: The Alaskan ramal fragments compare favorably with the array of L. lycaonoides material discussed in the literature cited above. Right ramus, F:AM 67180, was mentioned by Repenning (1967: 307, footnote 6 to table 8) as ‘‘ Xenocyon gigas ’’ following McKenna’s identification of it with Xenocyon (cited by Péwé and Hopkins, 1967: 269, footnote d to table). It was briefly described and figured by Youngman (1993). This specimen falls in the lower size range of X. lycaonoides , but agrees in all available characters. As in that taxon, there is often a short diastema between p2 and p3, and the anterior root of p2 lies slightly labial to the p 1 in a weakly imbricated fashion. Otherwise there is no break in the linear form of the dental row. The horizontal ramus is deep anteriorly, here being only a gentle taper forward. The subangular or digastric insertion of the ventral surface of the ramus just behind the toothrow is developed as in other X. lycaonoides specimens, and the anterior end of the masseteric fossa lies relatively high at the base of the ascending ramus. This fossa ends anteriorly, just behind the m3 alveolus. This region of the ramus is more completely preserved in F:AM 97110, but in a young adult jaw that has not yet reached adult proportions. The posterior part of the anterior alveolus and all of the posterior alveolus of m1 are preserved and show that the crown of this tooth was large, although probably not exceeding 32 mm in length judging from the length of the posterior root (16 mm). The coronoid process is short and high, the angular process has much growing cancellous bone, as does the tip of the coronoid, and the condyle is small. Clearly this region was actively growing since acquisition of the permanent dentition. This specimen is identified as X. lycaonoides chiefly on the morphology of m2, which has a very reduced metaconid and short and narrow talonid.

The individual represented from Old Crow River is also a very young adult; the jaw evidently has not reached adult size as the teeth are closely spaced, p2 is imbricated, and the ramus is shallow. A large mental foramen lies beneath the anterior root of p2, and there are two additional foramina approximately at mid-level on the ramus: one beneath the anterior root of p3, the other beneath the posterior root of the same tooth. Other X. lycaonoides individuals also show these foramina, although the most posterior may be below p4 (as in F: AM 67180). There is a shallow inflection in the ventral border of the ramus just behind the symphysis. The morphology of the p4 provides the most definite identification of either Xenocyon or Cuon rather than Canis lupus in the presence of a discrete second posterior cusp filling the space between the first posterior cusp and cingulum, and in the presence of an anterior cingulum with a low cusp. The proportions of the p4 (length, 14.8 mm, width, 6.7 mm from a cast) and large size of the anterior premolars implied by their roots (p2 about 11.0 mm, p3 12.7 mm) exceed those of the larger forms of Cuon alpinus (C. a. priscus and C. a. fossilis) or C. javanicus antiquus . Except for the shallower jaw, the specimen agrees best with X. lycaonoides , based on the morphology of the p4, the size and relationships of the p1–p3, and the distribution of the mental foramina.

The Saskatchewan specimens consist of two fragments from an old individual, one that lost M 2 in life. The premaxillary ( NMC 17825) and maxillary ( NMC 17824) could represent a single individual as far as preservation and wear on the teeth are concerned. The premaxillary contains I3, which, although badly worn, still shows a clear remnant of the medial cingulum. The M 1 is badly broken, but the large paracone and metacone can be seen. The protocone is relatively small and lacks a conule on the preprotocrista. The hypocone is very small, placed on the lingual cingulum posterior to the protocone ; the cingulum connects with the postprotocrista at the site of the metaconule; and a very subdued lingual cingulum extends anteriorly across the protocone to the anterior border opposite the site of the paraconule. The maxilla extends backward, forming a shelf where the M2 would lodge. It terminates in cancellous bone.

Discussion: The right ramus (F: AM 67180) allowed the first identification of the presence of Xenocyon in the New World ( Repenning, 1967; Péwé and Hopkins, 1967) and support- ed the presence of substantially older Pleistocene deposits in the Fairbanks area of Alaska. This specimen was figured and described by Youngman (1993), who thought that it should be referred to Cuon despite the retention of m3 and less modified molars. Likewise, the Canadian M1 agrees best with Xenocyon lycaonoides in size and in the presence of a hypocone and lingual cingulum.

We have discussed the age of the Cripple Creek Sump site in our description of the Canis lupus from that locality, but the age of the Wellsch Valley site needs further comment. The identification of the large canid as Xenocyon , rather than Borophagus , removes the necessity, on this basis, for an age older than the Pliocene–Pleistocene boundary. The known range of large Xenocyon lycaonoides seems limited to the medial Pleistocene in the Old World. The younger age also removes the necessity of having the Wellsch Valley occurrence of Microtis paroperarius represent the oldest in North America ( Repenning, 1987). The fission-track and paleomagnetic dating of the Wellsch Valley sequence is also resolved in favor of the fission-track date of 0.69 ± 0.11 Ma for the ash that lies at a reversed to normal magnetic polarity boundary. Barendregt et al. (1991) favored the latter as the Matuyama–Brunhes reversal. The electron spin resonance ( ESR) dates on elephant enamel from below the ash of 274 ± 35 Ka (Zymela et al., 1988) are too young, as suspected, but not as markedly discordant as they would have been if this section sampled the Matuyama Chron in the vicinity of the Olduvai Subchron as suggested by the previous identification of the canid.