Elephas? Mammuthus? Loxodonta? The question of the true ancestor of the smallest dwarfed elephant of Sicily

The smallest dwarfed elephants of Mediterranean islands occurred in Sicily during the Middle Pleistocene. First described by Busk (1867) on remains of Malta, Elephas falconeri was considered for more than fifty years as the last step of a progressive size reduction process, which started with Elephas antiquus and continued through ?Elephas (Palaeoloxodon) antiquus leonardii, E. mnaidriensis and ?Elephas melitensis. Actually, stratigraphic and geochemical data have demonstrated that the dwarfed forms were older than the medium-sized elephants of the E. mnaidriensis group, so the derivation of so-called ‘E.’ falconeri from E. antiquus is not sure. There are no conclusive osteological evidences for this; on the one hand the skull exhibits paedomorphic features and it is strongly modified in comparison with the Elephas antiquus skull, on the other hand the very simplified molar morphology does not exclude a phylogenetic relationship with the Palaeoloxodon line. However, the tusk morphology seems closer to the Loxodonta or Mammuthus lines. With respect to the postcranial region, it is difficult to establish how the load and size reduction and how the locomotion has influenced morphological modifications of the limb, in comparison with those of the ancestor. In spite of this, our preliminary investigations of E. falconeri from Spinagallo cave (Southeastern Sicily) have shown that the peculiar morphological features of the skull are basically due to the extensive development of the brain and the brain case, that maintains the respiratory axis turned forward and downward. Conversely the typical features of the fan link E. falconeri more to E. antiquus than any other Pleistocene elephant species. The Schreger angle pattern of the tusk seems to confirm this hypothesis. The analysis of carpal and metacarpal bones is still in progress and, even if we need more data to definitively solve the problem of origin of the smallest elephants of Sicily, a derivation from E. antiquus seems the most appropriate.