Palaeoloxodon

In 1924, Hikoshichiro Matsumoto circumscribed Palaeoloxodon as a subgenus of Loxodonta. It included the "E. antiquus—namadicus group", and he designated "E. namadicus naumanni Mak." as its type species.[1]

Palaeoloxodon was later thought to be a subgenus of Elephas, but this was abandoned by 2007.[5] In 2016, a DNA sequence analysis of P. antiquus suggested that its closest extant relative may be the African forest elephant, L. cyclotis. The paper argues that P. antiquus is closer to L. cyclotis than L. cyclotis is to the African bush elephant, L. africana, thus invalidating the genus Palaeoloxodon as currently recognized.[6] A second study suggested P. antiquus had a complex hybridization history, with over 60% of its DNA coming from a lineage closest to but outside the two extant Loxodonta species, around 6% from Mammuthus and 30% from a lineage closer to L. cyclotis than L. africana. The hybridisation probably took place in Africa, where Paleoloxodon was dominant for most of the Pliocene and Early Pleistocene.[7]

Life restoration of P. namadicus

Species of Palaeoloxodon are noted for their distinctive parieto-occipital crests present at the top of the cranium, which was used to anchor the splenius as well as possibly the rhomboid muscles to support the skull, which is proportionally large in comparison to other elephants. The tusks have relatively little curvature, and are proportionally large.[11]

Palaeoloxodon namadicus, showing the parieto-occipital crest at the top of the skull typical of Palaeoloxodon.

Palaeoloxodon first appears in the fossil record in Africa during the early Pliocene, around 4 Mya as the species Palaeoloxodon recki. P. recki was the dominant elephant in Africa for the Pliocene and most of the Pleistocene. A population of P. recki migrated out of Africa between 0.8 and 0.6 Mya, diversifying into the radiation of Eurasian Paleoloxodon species, including P. antiquus, P. namadicus, and P. naumanni, the precise relationships of the Eurasian taxa to each other are obscure in the absence of molecular evidence. P. recki became extinct in Africa around 0.5 Mya, being replaced by the modern genus Loxodonta. The arrival of P. antiquus in Europe co-incides with the extinction of Mammuthus meridionalis and its replacement by Mammuthus trogontherii, suggesting that it might have shared a similar dietary niche and outcompeted the former.[12] P. antiquus was able to disperse onto many islands in the Mediterranean, undergoing insular dwarfism and speciating into numerous distinct varieties of dwarf elephants. Palaeoloxodon fossils are abundant in China and are assigned to three species, P. namadicus, P. naumanni and P. huaihoensis.[13]

The last mainland European Palaeoloxodon faced extinction 30,000 years ago. The Japanese species possibly survived for a little longer afterwards. Among the last straight-tusked elephants were the Mediterranean dwarf species, which died out 3,000 years ago - possibly at the hands of human hunters and introduced predators.

A Palaeoloxodon population of undetermined species is claimed to have survived in northern China until 3,000 years ago. Li Ji and colleagues from the Institute of Geographic Sciences and Natural Resources Research, Beijing, argued that teeth previously believed to belong to Asian elephants were actually those of Palaeoloxodon. Whether these belong to a new, distinctive species or actual descendants of P. namadicus is unknown. They also argued that ritual bronze vessels depicting trunks with two "fingers" must be Palaeoloxodon (which are only known from bones; their trunk characteristics are unknown) because Asian elephants only have one.[14][15] Fossil elephant experts Victoria Herridge and Adrian Lister disagree with the assignment, stating that the claimed diagnostic dental features are actually contrast artifacts created due to the low image resolution of the figures in the scientific paper, which are not evident in better-quality photographs.[16] Given that the appearance of Palaeoloxodon trunks is unknown, and the bronze depictions of animals shown in the paper are highly stylized, the argument based on bronze vessels is also unreliable. Thus, these elephants are more likely Asian elephants, as originally believed.