Palaeoloxodon mnaidriensis is an extinct species of dwarf elephant belonging to the genus Palaeoloxodon, with remains attributed to the species from both Malta and Sicily during the Middle Pleistocene and Late Pleistocene. It is derived from the European mainland straight-tusked elephant (Palaeoloxodon antiquus). There is confusion about what remains should be attributed to the species, with a number of authors arguing that the Sicilian remains should be treated as a separate species.
Taxonomy and evolution Palaeoloxodon mnaidriensis was first named in 1874 based on material from Mnaidra gap in Malta by Andrew Leith Adams in 1874 as Elephas mnaidriensis. The lectotype of the species is the molar tooth NHM 44304, from Mnaidra gap. The species continued to be treated as a species of Elephas by later authors (who sometimes synonymised it with the species "Elephas melitensis" previously named from Maltese material) until a 1942 posthumous publication by Henry Fairfield Osborn, which considered it a member of the genus Palaeoloxodon. Later 20th century authors again considered the species a member of the genus Elephas, but by the 2000s its placement as a member of the genus Palaeoloxodon was generally accepted.
The temporal range of dwarf elephant material on Malta, including that of P. mnaidriensis, is poorly constrained, though almost certainly sometime during the Middle Pleistocene or Late Pleistocene. The evolutionary history of P. mnaidriensis on Malta is unclear, and it is possible that not all remains attributed to P. mnaidriensis on the island belong to the same species, with the species possibly being a wastebin to which all moderately dwarfed Sicilian-Maltese dwarf elephants have been attributed, with at least some molar teeth attributed to P. mnaidriensis from Għar Dalam cave on Malta having been found to be morphologically distinct from material attributed to P. mnaidriensis at other Maltese sites. Regardless of true relationships, all remains attributed to P. mnaidriensis are thought to ultimately descend from the continental European straight-tusked elephant (Palaeoloxodon antiquus), with the ancestors of the elephants first dispersing from southern Italy to Sicily and then from Sicily to Malta, with the distance between Sicily and Malta being greatly reduced during glacial periods due to the presence of a submarine plateau between Sicily and Malta that was exposed as dry land due to glacier-induced sea level lowering. While historically considered to have inhabited both Malta and Sicily, remains from Sicily are suggested to belong to a separate species, provisionally referred to as P. cf. mnaidriensis or P. ex gr. mnaidriensis. P. cf. mnaidriensis descended from a colonisation of Sicily by the straight-tusked elephant from mainland Italy during the late Middle Pleistocene, at earliest around 200,000 years ago, and probably by around 160,000 years ago, which replaced the even smaller, less than 1 metre (3 ft 3 in)-tall Palaeoloxodon falconeri, which had descended from a separate colonisation of Sicily by P. antiquus several hundred thousand years prior. Some of the Palaeoloxodon "mnaidriensis" remains from Għar Dalam may be the same species as the Sicilian P. cf. mnaidriensis, though other material from the cave may represent true P. mnaidriensis. The elephant species native to Malta and Sicily had reduced in body size as a result of insular dwarfism, a common phenomenon resulting from the colonisation of islands by large mammals. The much smaller body size of P. cf. mnaidriensis compared to P. antiquus, in combination with the relatively short period of time between colonisation and small body size suggests that the rate of dwarfism was relatively rapid.
Description Maltese dwarf elephants including P. mnaidriensis are generally only known from fragmentary skeletal remains. P. mnaidriensis proper from Malta was considerably smaller than P. cf. mnaidriensis from Sicily, based on the dimensions of its molar teeth, though larger than P. falconeri. The Sicilian P. cf. mnaidriensis has nearly 90% body size reduction compared to its straight-tusked elephant ancestor, with one estimate giving a shoulder height of about 1.8 m (5 ft 11 in) and a mean body weight of about 1,100 kg (2,400 lb) for specimens from Puntali Cave. Another estimate gives a shoulder height of 2 m (6 ft 7 in) and a weight of 1,700 kg (3,700 lb), which is comparable to the size of an African forest elephant. Like P. antiquus the head of Sicilian P. cf. mnaidriensis has a well developed parieto-occipital crest at the top of the skull. The teeth of Sicilian P. cf. mnaidriensis around 30% the size of those of P. antiquus. Relative to P. antiquus, the enamel of the teeth of Sicilian P. cf. mnaidriensis is thicker, and the density of lamellae on the teeth is higher, with the number of plates being slightly lower than those of the molars of P. antiquus. The limb bones of Sicilian P. cf. mnaidriensis are proportionally more robust than those of P. antiquus.
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