North American Miocene land mammals from Panama

Abstract

ABSTRACT Miocene land mammals are described from the Gaillard Cut Local Fauna based on a collection made by Stewart and Whitmore in the 1960s from Cucaracha Reach, former Canal Zone, Republic of Panama. In addition to the Order Rodentia described elsewhere, the land mammals represent three other orders (Carnivora [new record], Artiodactyla, Perissodactyla), including the canid Tomarctus brevirostris, indeterminant Amphicyonidae or Hemicyonidae, oreodont Merycochoerus matthewi, protoceratid Paratoceras wardi, horses Anchitherium clarencei and Archaeohippus sp., and rhinocerotids Menoceras barbouri and Floridaceras whitei. Despite its close proximity to South America, all of the taxa in the Gaillard Cut Local Fauna are of distinctly North American faunal affinities. Given their geological context in Panama and biochronology of the Cucaracha mammals as they are known from North America, the age of this assemblage is within an interval from latest Arikareean (Ar4) through early Barstovian (Ba2), between 19.5 and 14 Ma. Field relationships indicate a collection from a narrow stratigraphic zone: there does not appear to be temporal mixing from different land-mammal ages. Depending on the exact absolute age, which has not yet been determined, the Gaillard Cut Local Fauna either contains relictual ‘Hemingfordian’ species that persisted into the Barstovian, or ‘Barstovian’ indicators that originated earlier in Central America than they are known from North America. The predominance of low-crowned herbivores in the Gaillard Cut Local Fauna is interpreted to indicate forested and woodland habitats in the ancient Neotropics.