Relationships between North and South AmericanSmilodon

Abstract

Middle and Late Pleistocene representatives of the genus Smilodon in South and North America are here assigned to different species. The South American S. populator, which existed east of the Andes, is distinguished from the North American S. fatalis by the following characters: generally larger size, narrower skull with cranial part elongated relative to facial part, high nasals resulting in nearly straight dorsal profile, marked angle between mastoid and occipital plane, more “graviportal” limb bones, and extremely massive metapodials. Most differences are shown to arise from changes in allometric growth pattern; the difference is on a par with that between other valid and accepted species of carnivores. The detection of sexual dimorphism, the proper use of the ratio diagram, and subspecific versus specific differentiation are discussed. The Smilodon of the west coast region in South America (Peru, Ecuador) is S. fatalis, presumably a member of the Rancholabrean carnivore fauna that entered western South America in the Late Pleistocene.