Late Miocene immigrant carnivorans in California, USA highlight a coastal corridor for intercontinental dispersals

The Neogene interval witnessed three major waves of intercontinental dispersals by carnivoran mammals, mainly migrating from Eurasia to North America but with rare occurrences going in the opposite direction (e.g., Sthenictis, Leptarctus). The timing and composition of dispersers are thought to be controlled by filter-bridge mechanisms, but it is unclear what types of regional conditions promoted occasional dispersals outside of the three major waves. We study and report on new occurrences of small-bodied carnivorans from late Clarendonian-aged Black Hawk Ranch and Cuyama Valley fossil mammal assemblages in California. The relatively late occurrences of the mustelids Sthenictis and Hoplictis and the ailurid Alopecocyon in coastal regions of western North America suggest that nearshore dispersal corridors both facilitate and preserve faunal elements later than they might otherwise occur further inland. The availability of both marine- and terrestrially-derived food resources may be an important factor in allowing coastally dispersing taxa to be accommodated in those ecological communities compared to less heterogenous environments further inland.