Siwalik sabrecats: review and revised diagnosis of Megantereon fossils from the foothills of the Himalaya.

Abstract

The diagnosis of different fossil taxa in small collections from disparate geographical and temporal contexts is a common challenge in palaeontology. The likely number of morphospecies of the extinct sabretooth cat Megantereon is a classic example and subject of long-standing debate. While analyses of global fossil collections have provided insights and hypotheses, specimens from the foothills of the Himalaya-the Siwaliks-have been overlooked in recent treatments due to poor characterization and a confused taxonomic history. Here, this oversight is addressed. Craniodental fossils from the Siwaliks are revisited and their taxonomic status is reviewed. Morphological and metric characteristics are described, and qualitative and quantitative comparisons with congenerics are performed with published descriptions and datasets. The Lower Pleistocene Siwalik Megantereon are among the largest known forms in the genus. Advanced characteristics include reduced upper third premolars and long but comparatively narrow carnassial teeth. While dietary specialism can constrain morphological diversity, statistical analyses, including controls for body size effects, detected significant metric differences in the mandibles in comparison with congenerics. Within current paradigms, the status of Megantereon falconeri as a distinct morphospecies is upheld. A revised diagnosis is provided and the taxonomic affinities of M. falconeri are considered.