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.[4] 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 Loxodonta as currently recognized.[5] A second study suggested P. antiquus had a complex hybridsation 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 likely took place in Africa, where Paleoloxodon was dominant for most of the Pliocene and Early Pleistocene[6]

Some notable species are:

• P. antiquus (Europe, Middle East, Asia), was larger than the modern African elephant
• P. chaniensis (Crete), dwarf elephant
• P. cypriotes (Cyprus), dwarf elephant
• P. falconeri (Sicily and Malta), dwarf elephant
• P. mnaidriensis (Sicily), dwarf elephant
• P. namadicus (Asia), the largest in its genus, and possibly the largest terrestrial mammal ever
• P. naumanni (Japan), dwarf elephant and possible subspecies of E. namadicus
• P. recki (East Africa), the oldest (4.0 - 0.6 million years ago) and one of the largest species[7]

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

Palaeoloxodon is noted for its distinctive parieto-occipital crest present at the top of the cranium, which was used to anchor musculature to support the skull.[8]

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 Ma 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 Ma, 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.[9] P. antiquus was able to disperse onto many islands in the Mediterranean, undergoing insular dwarfism and speciating into numerous distinct varieties of dwarf elephant.

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.[10][11] 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.[12] 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.