Palaeoloxodon

Palaeoloxodon Temporal range: Early Pleistocene–Holocene PreꞒ Ꞓ O S D C P T J K Pg N ↓
Skeleton of the straight-tusked elephant (Palaeoloxodon antiquus) at the paleontological museum of the Sapienza University of Rome
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Proboscidea
Clade:	Elephantida
Superfamily:	Elephantoidea
Family:	Elephantidae
Genus:	†Palaeoloxodon Matsumoto, 1924[1]
Type species
Elephas namadicus naumanni Makiyama, 1924
Species
See text

Palaeoloxodon is an extinct

Analysis of mitochondrial genomes, including Palaeoloxodon individuals from Northern China indicates Palaeoloxodon individuals harboured multiple separate mitochondrial genome lineages derived from African forest elephants, some being more closely related to some West African forest elephant groups than to others. It is unclear as to whether this is the result of multiple hybridisation events, or whether multiple mitochondrial lineages were introgressed in a single event. It has been found that mitochondrial genome of Chinese Palaeoloxodon specimens clustered with a P. antiquus individual from western Europe, which belonged to a separate clade than other sampled European P. antiquus specimens. The relatively low divergence between the mitochondrial genomes of the European P. antiquus individual and the Chinese Palaeoloxodon specimens may indicate that the populations of Palaeoloxodon across Eurasia maintained gene flow with each other, but this is uncertain.^[6]

Diagram of the relationships of elephant mitochondrial genomes, after Lin et al. 2023:^[6]

Mainland species

• P. recki (Synonym: Elephas recki) (East Africa), the oldest species and ancestor of all later species
• P. jolensis
  (Synonym: Elephas iolensis) the last (late Middle-Late Pleistocene) representative of Palaeoloxodon in Africa
• P. antiquus
  (Synonym: Elephas antiquus) (Straight tusked elephant) (Europe, Western Asia)
• P. huaihoensis (China)
• P. namadicus (Synonym: Elephas namadicus)^[7] (Indian subcontinent, possibly also elsewhere in Asia), the largest in its genus, and possibly the largest terrestrial mammal ever
• P. naumanni (Synonym: E. namadicus naumanni) (Japan, possibly also China and Korea),^[8]
• ?P. turkmenicus known from a single specimen found in the Middle Pleistocene of Turkmenistan, with possibly attributable remains known from Kashmir, validity uncertain.^[9]

Mediterranean island dwarfs

These Mediterranean insular dwarf elephant species are almost certainly descended from P. antiquus

• P. creutzburgi (Crete)
• P. xylophagou (Cyprus
  )
• P. cypriotes (Cyprus)
• P. lomolinoi (Naxos)
• P. tiliensis (Tilos)
• P. mnaidriensis (Sicily and Malta)
• P. falconeri (Sicily and Malta)

Other indeterminate dwarf Palaeoloxodon species are known from other Greek islands, including Rhodes and Kasos.^[10]

Description

Most species of Palaeoloxodon are noted for their distinctive parieto-occipital crests present at the top of the cranium. The crest functioned to anchor muscle tissue, including the splenius as well as an additional muscle layer called the "extra splenius" (which was likely similar to the "splenius superficialis" found in Asian elephants, and which may have been an extension of the rhomboideus cervicis muscle) which wrapped around the top of the head to support it. The development of the crest is variable depending on the species, growth stage and gender, with females and juveniles having less developed or absent crests. The crest likely developed as a response to the large size of the head, which in proportional and absolute terms are the largest in size of any proboscideans.^[9] The skull is proportionally short and tall,^[11] with the premaxillary bones containing the tusks being flared outwards. The tusks have relatively little curvature, and are proportionally large,^[9] and somewhat twisted, with the tusk alveoli (sockets) being divergent from each other at least in Pleistocene species.^[11] These tusks could reach 4 metres (13 ft) in length, and probably over 190 kilograms (420 lb) in weight in the largest species, larger than any recorded in modern elephants.^[12]

The molar teeth of Palaeoloxodon species typically show a "dot-dash-dot" wear pattern,

• 
  Life restoration of Palaeoloxodon namadicus
• 
  Skeletal diagram of an adult male

  Palaeoloxodon antiquus
• 
  Third molar teeth of Palaeoloxodon huaihoensis
• 
  Partial skull of Palaeoloxodon namadicus, showing the parieto-occipital crest at the top of the skull
• 
  Size comparison of the dwarf elephant Palaeoloxodon falconeri, one of the smallest elephants known
• 
  Skull of Palaeoloxodon antiquus in front-on view, showing flared premaxillae with divergent tusks

Ecology

Species of Palaeoloxodon are thought to have similar social behaviour to modern elephants, with herds of adult females and juveniles, as well as solitary adult males.^[17] The African species of Palaeoloxodon, as well as P. namadicus are suggested to have been grazers,^[18][19] while P. antiquus is suggested to have been a variable mixed feeder that consumed a considerable amount of browse.^[20]

Evolution

Palaeoloxodon first unambiguously appears in the fossil record in Africa during the

Middle Pleistocene around 0.8 to 0.6 Mya, diversifying into the radiation of Eurasian Palaeoloxodon species, including P. antiquus, and P. namadicus. The precise relationships of the Eurasian taxa to each other are obscure.^[22] 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.^[22] 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.^[23] However, the relationships of Chinese Palaeoloxodon are currently unresolved and it is unclear how many species were present in the region.^[9]

Extinction

The timing of the extinction of the last Paleoloxodon species in Africa,

P. iolensis, is uncertain. While often suggested to have gone extinct during the Late Pleistocene, most specimens of the species are poorly dated and dating of specimens from Kenya suggests that it went extinct around 130,000 years ago, at the end of the Middle Pleistocene.^[18] Most Eurasian species of Palaeoloxodon became extinct towards the end of the Last Glacial Period. The youngest records of P. antiquus are from the Iberian Peninsula, dating to 50-34,000 years ago, with footprints from the southern part of the peninsula possibly extending the record to 28,000 years ago.^[24] The youngest Japanese records of P. naumanni date to around 24,000 years ago.^[25] The timing of extinction of Chinese Palaeoloxodon and Indian P. namadicus is uncertain, but claims of a Holocene survival are not substantiated for either region.^[26][27][28] The youngest dates for the Sicilian dwarf elephant P. cf. mnaidriensis date to 32-20,000 years ago,^[29] while the youngest dates for the Cyprus dwarf elephant P. cypriotes are around 12,000 years ago.^[30] P. tiliensis from the Greek island of Tilos was suggested to have survived as recently as 3,500 years Before Present based on preliminary radiocarbon dating done in the 1970s, which would make it the youngest surviving elephant in Europe, but this has not been thoroughly investigated.^[10]

Relationship with humans

Further information: Straight-tusked_elephant § Relationship_with_humans, Palaeoloxodon_recki § Relationship_with_humans, and Palaeoloxodon_naumanni § Relationship_with_humans

Remains of the species P. recki, P. antiquus and P. naumanni have been found associated at a number of sites with stone stools and/or with cut marks on their bones, indicating that they were butchered, with some sites presenting clear evidence of hunting. These sites span from the Early Pleistocene, at least 1.3 but possibly as early as 1.6 million years ago to around 40,000 years ago, with the makers of the sites including both archaic humans (P. antiquus and P. recki) and modern humans (P. naumanni).^[31][32][33]

References

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