Palaeoloxodon namadicus

Palaeoloxodon namadicus is an extinct species of prehistoric elephant known from the early Middle to Late Pleistocene of the Indian subcontinent, and possibly also elsewhere in Asia. The species grew larger than any living elephant, and some authors have suggested it to have been the largest known land mammal, based on extrapolation from fragmentary remains, though these estimates are speculative.

Palaeoloxodon namadicus
Temporal range:
Skull at the Indian Museum, Kolkata
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Proboscidea
Family: Elephantidae
Genus: †Palaeoloxodon
Species:
†P. namadicus
Binomial name
†Palaeoloxodon namadicus
(Falconer & Cautley, 1846)

Description
Life restoration

Some authorities historically regarded P. namadicus and the European straight-tusked elephant (P. antiquus) as the same species due to their similar skull morphology.[1] P. namadicus shares similarities to other species of Palaeoloxodon, which includes a large crest (the parieto-occipital crest) at the top of the skull that anchored the splenius muscles used to support the head. Later research suggested that P. namadicus can be distinguished from P. antiquus by its less robust (more elongate) limb bones and more stout cranium (including a better developed parieto-occipital crest).[2]

Fragmentary skull of a female individual, showing parieto-occipital crest at the top of the skull

Size

Several studies have attempted to estimate the size of P. namadicus, as well as other prehistoric proboscideans, usually using comparisons of thigh bone length and knowledge of relative growth rates to estimate the size of incomplete skeletons. One partial skeleton found in India in 1905 had femurs that likely measured 165 centimetres (5.41 ft) long when complete, suggesting a total shoulder height of 4.5 metres (14.8 ft) for this individual elephant.

Two partial femurs found in the 19th century at Sagauni are suggested to have measured 160 centimetres (5.2 ft), when complete, suggesting a shoulder height of 4.35 metres (14.3 ft) and a weight of 13 tonnes (14.3 short tons) for this individual.[3] A fragmentary femur from the same locality was said to be almost a quarter larger; assuming it is about 20% larger, volumetric analysis yields a femur length of 190 centimetres (6.2 ft) and a speculative size estimate of 5.2 metres (17.1 ft) tall at the shoulder and 22 tonnes (24.3 short tons) in body mass, which if correct would make P. namadicus possibly the largest land mammal ever, exceeding even paraceratheres in size. However this estimate based on the "distal femur portion" the author stated should be "taken with a grain of salt" , as the author himself could only suspect that "fossils are likely stored in the Indian Museum of Kolkata; until such a collection can be revised, this size estimate will remain speculative."[3] In 2023, Paul and Larramendi estimated that the specimen identified as cf. P. namadicus would have weighed 18–19 tonnes (19.8–20.9 short tons).[4]

Ecology

Based on stable isotope ratios of carbon and oxygen and the morphology of their teeth, it is suggested that P. namadicus tended towards a grazing diet. Its arrival on the subcontinent co-incides with a shift in the diet of contemporaneous Elephas hysudricus (the ancestor of the living Asian elephant) from a grazing diet towards browsing-mixed feeding, possibly as a result of niche partitioning.[5]

Evolution and extinction

P. namadicus is primarily known from the Indian subcontinent.[2] Remains attributed to P. namadicus have also been reported across Southeast Asia (including Malaysia, Myanmar, Laos, and Vietnam, and the island of Sulawesi in Indonesia) and as well as southern China.[6][7] However, the status of Chinese Palaeoloxodon is unresolved, with other authors considering the remains to belong to P. naumanni (otherwise known from Japan) or the separate species P. huaihoensis. The postcranial remains of Palaeoloxodon from China are substantially more robust than Indian P. namadicus and in many respects are more similar to those of P. antiquus, making their referral to P. namadicus questionable.[2]

The oldest specimens of P. namadicus in India are thought to be over 700,000 years old, dating to the early Middle Pleistocene,[2] originating, like other Eurasian Palaeoloxodon species from a migration of a population of P. recki out of Africa.[8] Palaeoloxodon namadicus is thought to have become extinct during the Late Pleistocene, making it one of four megafauna species native to the Indian subcontinent suggested to have become extinct during the Late Pleistocene, alongside fellow proboscidean Stegodon namadicus, the equine Equus namadicus, and the hippopotamus Hexaprotodon.[9][10] The exact time of extinction of these taxa is unclear to the uncertainly surrounding known dates, many of which were taken decades ago and based on methods that did not involve directly dating the bone itself, with methods that are prone to error.[10]

References
  1. Ferretti, M.P. (May 2008). "The dwarf elephant Palaeoloxodon mnaidriensis from Puntali Cave, Carini (Sicily; late Middle Pleistocene): Anatomy, systematics and phylogenetic relationships". Quaternary International. 182 (1): 90–108. Bibcode:2008QuInt.182...90F. doi:10.1016/j.quaint.2007.11.003.
  2. Larramendi, Asier; Zhang, Hanwen; Palombo, Maria Rita; Ferretti, Marco P. (February 2020). "The evolution of Palaeoloxodon skull structure: Disentangling phylogenetic, sexually dimorphic, ontogenetic, and allometric morphological signals". Quaternary Science Reviews. 229: 106090. Bibcode:2020QSRv..22906090L. doi:10.1016/j.quascirev.2019.106090. S2CID 213676377.
  3. Larramendi, Asier (2015). "Proboscideans: Shoulder Height, Body Mass and Shape". Acta Palaeontologica Polonica. doi:10.4202/app.00136.2014.
  4. Paul, Gregory S.; Larramendi, Asier (June 9, 2023). "Body mass estimate of Bruhathkayosaurus and other fragmentary sauropod remains suggest the largest land animals were about as big as the greatest whales". Lethaia. 56 (2): 1–11. doi:10.18261/let.56.2.5. Retrieved June 9, 2023.
  5. Patnaik, Rajeev; Singh, Ningthoujam Premjit; Paul, Debajyoti; Sukumar, Raman (2019-11-15). "Dietary and habitat shifts in relation to climate of Neogene-Quaternary proboscideans and associated mammals of the Indian subcontinent". Quaternary Science Reviews. 224: 105968. doi:10.1016/j.quascirev.2019.105968. ISSN 0277-3791. S2CID 210307849.
  6. Louys, Julien; Curnoe, Darren; Tong, Haowen (January 2007). "Characteristics of Pleistocene megafauna extinctions in Southeast Asia". Palaeogeography, Palaeoclimatology, Palaeoecology. 243 (1–2): 152–173. doi:10.1016/j.palaeo.2006.07.011.
  7. Geer, Alexandra A. E.; Bergh, Gerrit D.; Lyras, George A.; Prasetyo, Unggul W.; Due, Rokus Awe; Setiyabudi, Erick; Drinia, Hara (August 2016). "The effect of area and isolation on insular dwarf proboscideans". Journal of Biogeography. 43 (8): 1656–1666. doi:10.1111/jbi.12743. ISSN 0305-0270. S2CID 87958022.
  8. Lister, Adrian M. (2004), "Ecological Interactions of Elephantids in Pleistocene Eurasia", Human Paleoecology in the Levantine Corridor, Oxbow Books, pp. 53–60, ISBN 978-1-78570-965-4, retrieved 2020-04-14
  9. Jukar, A.M.; Lyons, S.K.; Wagner, P.J.; Uhen, M.D. (January 2021). "Late Quaternary extinctions in the Indian Subcontinent". Palaeogeography, Palaeoclimatology, Palaeoecology. 562: 110137. doi:10.1016/j.palaeo.2020.110137. S2CID 228877664.
  10. Turvey, Samuel T.; Sathe, Vijay; Crees, Jennifer J.; Jukar, Advait M.; Chakraborty, Prateek; Lister, Adrian M. (January 2021). "Late Quaternary megafaunal extinctions in India: How much do we know?". Quaternary Science Reviews. 252: 106740. doi:10.1016/j.quascirev.2020.106740. S2CID 234265221.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.