Research overview: the three species of Smilodon and their taxonomic boundaries

This overview surveys how palaeontologists distinguish the three generally recognized species of the sabertooth genus Smilodon. The earliest and smallest, Smilodon gracilis, appears in the early Pleistocene of North America and is regarded as ancestral to the later forms. Smilodon fatalis, abundant at Rancho La Brea, is the iconic mid-sized North American species, while Smilodon populator of South America is the largest and most robust, with a notably elongated skull and forelimbs. The survey covers the diagnostic cranial, dental, and postcranial characters used to separate them, ongoing disputes over regional variants and synonymies, and how the Great American Biotic Interchange shaped their distributions. It emphasizes why consistent species definitions matter for reconstructing sabertooth evolution and ecology.