Taxonomic and biogeographic implications of late Miocene- Pliocene Samotherium (Giraffidae) from As-Sahabi, Libya: morphometric and machine learning approaches

This study presents a comprehensive analysis of seven giraffid astragali from upper Miocene-Pliocene As-Sahabi deposits (Libya), combining morphological examination with machine learning approaches to resolve long-standing taxonomic uncertainties. Using Linear Discriminant Analysis (LDA)—the most accurate of four tested models (median accuracy = 0.61, κ = 0.48)—we identified two distinct Samotherium species: S. major (4 specimens) and S. boissieri (3 specimens). Morphometric analyses revealed a significant size difference (S. major was larger by 10.1–12.3%, p < 0.05), supported by geographic segregation and stratigraphic distribution mirroring patterns observed in Samos, Greece. The S. boissieri specimens were exclusively found in the locality P32 (Qarat Makada Member, potentially unit T), while S. major occurred in both Unit U1 of Sahabi Formation and the overlying Qarat Weddah Formation. These findings confirm the extension of the Greco-Iranian bioprovince into North Africa during the late Miocene (MN11-13) and highlight As-Sahabi's importance as a biogeographic crossroads. Faunal associations suggest that S. boissieri inhabited more open landscapes compared with S. major's mixed-habitat preference, indicating ecological partitioning within the Samotherium species.