ATTRIBUTION OF THE CHINJI ATYPICAL “HOMINOID” CANINES

The atypical upper canines are, in fact, suid canines. The first evidence of this came when I began to search through the Siwalik collections at the Geological Survey of Pakistan during the 1993 field season. In the suid collections, I found an isolated upper canine (from a Dhok Pathan locality) that is nearly identical to the atypical Chinji canines in every respect, differing only in being strongly compressed bucco-lingually (Figure 5). Like the atypical canines, it has a distinct mesial wear facet but no distal wear.

Why this one canine should have been placed with the Suidae is unclear. It may be because this was the first canine of this type discovered by Harvard-GSP team members, who, as noted earlier, had found a number of genuine Sivapithecus upper canines, including some still in jaws, and who may have correctly recognized this canine as non-hominoid. According to its catalogue number, it was found several years before GSP 23124 and the two atypical canines described by Raza et al. (1983). Nevertheless, this canine was itself unassociated, so it was possible that its assignment to the Suidae was incorrect.

More definitive evidence that this canine and the atypical canines from the Chinji Formation were those of suids came during a search of the suid collections at the Kenya National Museums in 1996. This search produced a skull of the early Miocene suid Hyotherium dartevellai with the upper canines in place (figured in Cooke and Wilkinson 1978, figure 22.4). These closely resemble the Siwalik atypical canines morphologically and also have mesial wear facets but no distal wear facets. Confirmation came soon after with the publication of van der Made’s (1996) monograph on the Listriodontidae, in which are figured and described a number of female suid canines that are similar or identical to the atypical Siwalik canines from the Chinji Formation. Figured canines of Bunolistriodon from Maboko (van der Made 1996, plate 26) and Paşalar (plate 19), and Listriodon canines from Paşalar (plate 35) and Arroyo del Val IV (plate 38), in particular closely resemble the atypical Siwalik canines. While a few heavily worn canines figured by van der Made have both mesial and distal wear facets, most have only a mesial facet like all the atypical Siwalik canines. Interestingly, in van der Made’s description of Listriodon pentapotamiae from the Siwalik Chinji Formation, there is no mention of female canine morphology, presumably because all of the female canines were in the hominoid collection. In fact, it is almost surely to this species that the atypical Chinji canines belong, rather than to the other Chinji suid, the non-listriodont Conohyus sindiensis.