Geographic and temporal variability in Pleistocene lion-like felids: Implications for their evolution and taxonomy

Abstract

Several taxa of lions occurred in the Pleistocene of the Northern Hemisphere. Although crania of these large cats are relatively rare in the fossil record, they allow us to assess size and shape differences among Pleistocene lions from Europe, Asia, and North America (Panthera fossilis, P. spelaea, P. atrox) and to compare them with the extant P. leo. We use basic 14 morphometric data (cranial length/width dimensions, auditory bulla diameters, cranial profile) including data on sex and ontogenetic age in 44 fossil and eight recent specimens, along with their geological age and altitude. We show that: first, crania of the P. fossilis (including P. "intermedia") differs from crania of the Last Glacial P. spelaea and the extant P. leo. Second, P. spelaea shows a high morphologic variation in cranial morphology across its geographic range, with partial morphological segregation between the Western European and Eastern European assemblages. However, the main axis of morphological variation between geographic forms of P. spelaea and P. fossilis-"intermedia" correlates with size (in contrast to major differences relative to P. atrox), and cranial data thus do not consistently differentiate between these geographically and temporally-separated forms. These forms probably represent ecologically-differing geographic populations of the same chronospecies rather than distinct species. Geographic differences are driven by allometry, although other traits such as the teeth may allow their separation in the future analyses. However, the relationships in cranial morphospace still reveal geographic relatedness among subspecies: P. spelaea assemblage from the Western Europe is very similar to P. fossilis-"intermedia", and contrasts with P. spelaea from the Eastern Europe and Asia. On one hand, such patterns suggest that the western P. spelaea is more related to P. fossilis-"intermedia" lineage and the eastern P. spelaea is related to individuals from Siberia. On the other hand, the similarity between the West-European specimens of P. spelaea (as immigrants from the East) and specimens of P. fossilis-"intermedia" can reflect functional convergence to similar environmental and climatic conditions prevailing in Western Europe.

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