Regional body-mass dynamics and long-term mixed feeding diet in the Pleistocene Stephanorhinus hemitoechus (Mammalia, Rhinocerotidae) from Western Europe

We synthesize body mass, limb gracility, and diet in Stephanorhinus hemitoechus from 57 western European cohorts (MIS12–MIS3) using body mass-estimation equations, metapodial gracility indices, dental mesowear, and microwear. Two region-specific dynamics emerge: 1) in Northern Europe, cohorts are consistently heavier than Mediterranean contemporaries but remain broadly stable through time; 2) in the Mediterranean core range, body masses are stable from MIS 12 to MIS 7, rise in MIS 6, and then plateau through MIS 3. Gracility indices show little variations through time. Mesowear and microwear indicate a durable mixed-feeding strategy across the species' range, with northern populations incorporating slightly more grass. In specimens with paired estimated body mass and mesowear (n = 14), we found that higher grass intake relates to lower body mass, suggesting that diet modulates, but does not drive, size variation. These results support a distinction between core-range cohorts and peripheral interglacial incursions: in the North, climatic deterioration likely led to local extirpation rather than in situ size adjustment, as instead observed in the Mediterranean area. Near the last occurrences (MIS 4–3), several assemblages (Axlor, El Castillo) depart from year-round mixed feeding and show seasonal specialization toward grazing or browsing, consistent with colder, floristically simplified landscapes and heightened competition. We propose that this late loss of year-round dietary flexibility, coupled with the prior Mediterranean body-mass increase, increased vulnerability and may have contributed to extinction.