Systematics and palaeoneurology of a new Pliocene raccoon dog (Canidae, Nyctereutes) from Jradzor (Armenia)

We describe a new fossil raccoon dog from the Late Pliocene site of Jradzor, Armenia, a key site to understand biogeographic connections and dispersal between Asia, Europe, and Africa. The specimens analysed here for the first time exhibit a mosaic of primitive and derived cranial and dental traits, distinguishing them from known taxa such as Nyctereutes tingi (e.g. elongated cranium, reduced subangular lobe), N. sinensis (e.g. molar proportions, sulcal pattern), and N. megamastoides (e.g. absence of squared M1 morphology). Virtual reconstruction of the endocranium reveals a unique sulcal and gyral pattern, including a parenthesis-shaped gyrus sigmoideus and a deeply developed sulcus pseudosylvius , placing it morphologically closer to Canini than extant Vulpini. Considering these features, we propose to ascribe it to a new Nyctereutes species. Morphometric and geometric morphometric analyses support its taxonomic distinctiveness and suggest ecological and behavioural affinities with jackal-like canids. Notably, the relative development of the rostral portion of the cerebrum implies a social structure more complex than that of extant Nyctereutes , suggesting the possibility of seasonal pack formation. Additionally, we reassess several neuroanatomical traits previously considered diagnostic, such as the cerebellar vermis and sulcus endomarginalis , revealing greater variability within Nyctereutes and challenging previous phylogenetic assumptions. These findings underscore the Pliocene diversification of the genus and highlight the Caucasus as a pivotal region in canid evolution. The erection of a new Nyctereutes species enriches our understanding of canid paleobiology and provides new perspectives on the evolutionary trajectories of hypocarnivorous canids.