1268


Journal of Paleontology 91(6):1258–1271


Figure 8. Scatter-plot diagrams of the m1 length and width (1) and the m1 width and m1 width/length ratio (2) in species of the genus Eucyon. Symbols are explained in the legend.


Discussion


Vekua (1972), who was the first to report canid material from Kvabebi, described several cranial and postcranial elements of Nyctereutes megamastoides and a single hemimandible frag- ment identified as Canis sp. Our revision confirms, in general terms, these original taxonomic attributions (Vekua, 1972; as updated in Agustí et al., 2009), with additional recognition of a third taxon (Vulpes cf. V. alopecoides). The occurrence of three sympatric canids is not surprising,


since the family shows a great degree of sympatry. At present, Africa, Asia, and SouthAmerica support the greatest canid diversity, with >10 living species for each continental area. The red foxes, golden jackals, and gray wolves are each sympatric withmore than ten other canids (from different geographical regions) within one location; however, canid diversity is usually limited to a maximum of four or five species (Sillero-Zubiri and Macdonald, 2004). The fossil record of canid diversity does not contradict this rule, and the Kvabebi record documents a guild of three sympatric canids.


Nyctereutes.—The first occurrence of Nyctereutes is in early Pliocene, with the species Nyctereutes tingi fromthe Yushe Basin and Nyctereutes donnezani from Western European localities. Subsequently, a more derived species (N. sinensis)appears in some Chinese sites, together with the more primitive N. tingi (Teilhard de Chardin and Pei, 1941). By the late early-middle Pleistocene, N. sinensis seems to have been replaced by another derived taxon (Nyctereutes sp. in Tedford and Qiu, 1991). In contrast to the coexistence in Asia of primitive and derived forms, in late Pliocene localities inWestern European (e.g., San Giusto, Villaroya, Perrier-Etouaires) raccoon dog-like canids are repre- sented by the derived species N. megamastoides (Bartolini Lucenti, 2017). This species, probably related to N. donnezani, may be regarded as the European counterpart ofN. sinensis for the retention of comparable derived features. In the early Pleistocene, there is no or little record of Nyctereutes in Eurasia. The extant N. procyonoides appears in


the Middle Pleistocene deposits of Zhoukoudian (localities 1 and 13). Even though the phylogenetic relationships of late Pliocene Eurasian species of Nyctereutes are still a matter of debate (see Tedford and Qiu, 1991; Monguillon et al., 2004), we deem a closer relation plausible between the extant N. procyonoides and N. sinensis. The occurrence in the Kvabebi sample of Nyctereutes megamastoides, as identified by Vekua (1972), testifies to the wide geographic range expansion of this western European taxon. Recently, Asahara and Takai (2016) attempted to infer


dietary preferences in extant and extinct Nyctereutes species using the ratio of m2 and m1 surfaces (see also Kavanagh et al., 2007). Their analyses confirmed that primitive species like N. donnezani and N. tingi had omnivorous diets. In addition, the authors found that N. sinensis had a more carnivorous m2/m1 score than for N. megamastoides, suggesting a more omnivorous diet for the latter. Using the methodology of Asahara and Takai (2016), Nyctereutes from Kvabebi possesses an m2/m1 of ~0.53, intermediate between the two derived species. The Kvabebi sample fits with the general framework proposed by Asahara and Takai (2016), in which members of the genus Nyctereutes underwent dietary transitions or had considerable dietary plasticity in their evolution.


Vulpes.—The genus Vulpes appeared in the late Miocene (ca. 9Ma, Hemphillian) of North America (Tedford et al., 2009). As with other members of the subfamily Caninae, it expanded its range early into the Old World, as testified by the African species Vulpes riffautae de Bonis et al., 2007 from the late Miocene Toros-Menalla site and by the early Pliocene Chinese Vulpes beihaiensis Qiu and Tedford, 1990 from the Yushe Basin, aswell as Vulpes qiuzhudingiWang et al., 2014 fromthe Tibetan Plateau (the Zanda and Kundun basins). This latter large-sized species possesses remarkable hypercarnivorous adaptations, suggesting a close relationship to the extant V. lagopus. The earliest European record of Vulpes is that of early-late


Pliocene V. praecorsac in the Odessa catacombs (MN 15, Odintzov, 1965). This small-sized fox has been historically


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