The straight-tusked elephant (Palaeoloxodon antiquus) is an extinct species of elephant that inhabited Europe and Western Asia during the Middle and Late Pleistocene. One of the largest known elephant species, mature fully grown bulls on average had a shoulder height of 4 metres (13 ft) and a weight of 13 tonnes (29,000 lb). Straight-tusked elephants likely lived very similarly to modern elephants, with herds of adult females and juveniles and solitary adult males. The species was primarily associated with temperate and Mediterranean woodland and forest habitats, flourishing during interglacial periods, when its range would extend across Europe as far north as Great Britain and Denmark and eastwards into Russia, while persisting in southern Europe during glacial periods. Skeletons found in association with stone tools and wooden spears suggest they were scavenged and hunted by early humans, including Homo heidelbergensis and their Neanderthal successors.
The species is part of the genus Palaeoloxodon (whose other members are also sometimes called straight-tusked elephants), which emerged in Africa during the Early Pleistocene, before dispersing across Eurasia at the beginning of the Middle Pleistocene, with the earliest record of Palaeoloxodon in Europe dated to around 800–700,000 years ago. The straight-tusked elephant is the ancestor of a number of species of dwarf elephants that inhabited islands in the Mediterranean. The species became extinct during the latter half of the Last Glacial Period, with the youngest remains found in the Iberian Peninsula, dating to around 44,000 years ago. Possible even younger records include a single tooth from the Netherlands that has been dated to around 37,000 years ago, and footprints from the southern part of the Iberian peninsula dated to 28,000 years ago.
Skeletal diagram of a 3.8 metre tall 40 year old adult male compared to a humanModel
The body, including the pelvis, of P. antiquus was broad relative to extant elephants. The forelimbs, particularly the humerus, and the scapula are proportionally longer than those of living elephants, resulting in a high position of the shoulder. The head represents the highest point of the animal, with the back being somewhat sloped though irregular in shape. The spines of the back vertebrae are noticeably elongate. The tail was relatively long. Although not preserved, the body was probably only sparsely covered in hair, similar to extant elephants, and probably had relatively large ears.[3]
The skull is proportionally both very wide and tall.[3] Like many other members of the genus Palaeoloxodon, P. antiquus possesses a well-developed growth of bone at the top of the cranium above the nasal opening called the parieto-occipital crest, originating from the occipital bone of the skull roof which projects forwards and overhangs the rest of the skull. The crest was probably an anchor for muscles, including the splenius, as well as an additional muscle layer that wrapped around the top of the head, called the "extra splenius". The latter was likely similar to the "splenius superficialis" found in Asian elephants. The crest likely developed to support the very large size of the head, as the skulls of Palaeoloxodon are the largest proportionally and in absolute size among proboscideans. Two morphs of P. antiquus were previously thought to exist in Europe on the basis of differences in the parieto-occipital crest, one more similar to the South Asian Palaeoloxodon namadicus. These differences were shown to be age-related (ontogenetic variation), with the crest being more pronounced in older individuals, as well as due to distortion during fossilisation (taphonomic variation). P. antiquus differs from P. namadicus in having a less stout cranium and more robust limb bones, and in lacking a teardrop-shaped indentation behind the eye socket (infraorbital depression).[4] The premaxillary bones (which contain the tusks) are fan-shaped and very broad in front view. The tusks are very long relative to the size of the body and vary from straight to slightly curved.[3] The teeth are high crowned (hypsodont), with each third molar having approximately 16–21 lamellae (ridges).[5]
Size
Size diagram of P. antiquus compared to humans, showing an average sized male (dark yellow) and female (purple) and estimated size of the largest known specimens (transparent yellow)
The species was sexually dimorphic, with males being substantially larger than females; this size dimorphism was more pronounced than in living elephants. P. antiquus was on average considerably larger than any living elephant, and among the largest known land mammals to have ever lived. Under optimal conditions where individuals were capable of reaching full growth potential, 90% of mature fully grown straight-tusked elephant bulls are estimated to have had shoulder heights in the region of 3.8–4.2 m (12.5–13.8 ft) and a weight between 10.8–15 tonnes (24,000–33,000 lb). For comparison, 90% of mature fully grown bulls of the largest living elephant species, the African bush elephant under optimal growth conditions have heights between 3.04 to 3.36 metres (10.0 to 11.0 ft) and masses between 5.2–6.9 tonnes (11,000–15,000 lb).[3][6] Extremely large bulls, such as those represented by a now lost pelvis and tibia collected from Spain in the late 19th century, may have reached shoulder heights of 4.6 m (15.1 ft) and body masses of over 19 tonnes (42,000 lb).[6] Adult males had tusks typically around 3.5–4 metres (11–13 ft) long, with masses comfortably exceeding 100 kilograms (220 lb). The preserved portion of one particularly large and thick tusk from Aniene, Italy, is 3.9 metres (13 ft) in length, has a circumference of around 77 centimetres (30 in) where it would have exited the skull, and is estimated to have weighed over 190 kilograms (420 lb) in life.[7] Females reached shoulder heights and weights rarely exceeding 3 metres (9.8 ft) and 5.5 tonnes (12,000 lb) respectively, for comparison, female African bush elephants reach an average shoulder height of 2.6 metres (8.5 ft) and body mass of 3 tonnes (6,600 lb) under optimal growth conditions.[3] Newborn and young calves were likely around the same size as those of modern elephants.[8] A largely complete 5 year old calf from Cova del Rinoceront in Spain was estimated to have a shoulder height of 178–187 centimetres (5.8–6.1 ft) and a body mass of 1.45–1.5 tonnes (3,200–3,300 lb), which is comparable to a similarly aged African bush elephant.[9]
History of discovery, taxonomy and evolution
Early finds and research history
In the second century AD, the Greek geographer Pausanias remarked that the Megalopolis region in the central part of the Peloponnese peninsula in southern Greece was known for its enormous bones, which Pausanias reported were considered to be those of giants who died during the Gigantomachy, a mythic climactic battle between the giants and the Greek gods. Given that this region is today known for its straight-tusked elephant fossils, it is plausible that at least some of the giant bones to which Pausanias referred were those of straight-tusked elephants.[10]
In 1695, remains of a straight-tusked elephant were collected from travertine deposits near Burgtonna in what is now Thuringia, Germany. While these remains were originally declared to be purely mineral in nature by the Collegium Medicum in the nearby city of Gotha, Wilhelm Ernst Tentzel, a polymath in the employ of the ducal court of Saxe-Gotha-Altenburg, correctly identified them as elephant remains.[11] The Burgtonna skeleton was one of the specimens that Johann Friedrich Blumenbach described in his publication naming the woolly mammoth (Mammuthus primigenius, originally Elephas primigenius) in 1799.[12] The remains of straight-tusked elephants continued to be attributed to woolly mammoths until the 1840s.[2]
The straight-tusked elephant was scientifically named in 1847 by British palaeontologists Hugh Falconer and Proby Cautley as Elephas (Euelephas) antiquus.[13][2] The type specimen is a mandible (lower jaw) with a second molar (M2006). The exact provenance of the specimen is unknown, though it probably originates from Britain, and possibly the site of Grays in Essex, southeast England.[2] The common name "straight-tusked elephant" was used for the species as early as 1873 by William Boyd Dawkins.[14] In 1924, the Japanese paleontologist Matsumoto Hikoshichirō assigned E. antiquus to his new taxon Palaeoloxodon, which he classified as a subgenus of Loxodonta (which includes the living African elephants).[15][2] The species has a confused taxonomic history, with at least 21 named synonyms.[2] In publications in the 1930s and 1940s, Henry Fairfield Osborn assigned the species to its own genus Hesperoloxodon, which was followed by some later authors, but is now rejected.[10][2] In his widely cited 1973 work, Origin and evolution of the Elephantidae, Vincent J. Maglio sunk P. antiquus into the South Asian P. namadicus, as well as Palaeoloxodon back into Elephas (which contains the living Asian elephant). While the sinking of Palaeoloxodon into Elephas (with Palaeoloxodon sometimes being treated as a subgenus of Elephas) gained considerable traction in the following decades, today both P. antiquus and Palaeoloxodon are considered distinct.[4]
DNA analysis
Phylogeny showing the placement of Palaeoloxodon antiquus in relation to other elephantids based on nuclear genomes, after Palkopoulou et al. 2018, demonstrating that it received substantial introgression of genes from African forest elephants, and to a lesser extent mammoths.[16]
Traditionally, Palaeoloxodon species were thought to share a close common ancestry with Asian elephants and other species of Elephas, which was based on a number of morphological similarities between the two groups.[4] In 2016, a mitochondrial DNA sequence analysis instead found that the mitochondrial genome of P. antiquus was nested within those of the African forest elephant (Loxodonta cyclotis), with analysis of a partial nuclear genome supporting a closer relationship to L. cyclotis than to the African bush elephant (L. africana).[17][18] A subsequent study published in 2018 that includes some of the same authors presented a complete nuclear genome sequence, indicating a more complicated relationship between straight-tusked elephants and other species of elephants. According to this study, the lineage of Palaeoloxodon antiquus was the result of reticulate evolution, with the majority of the genome of straight-tusked elephants deriving from a lineage of elephants that was most closely related but basal to the common ancestor of forest and bush elephants (~60% of total genomic contribution), which had significant introgressed ancestry from African forest elephants (>33%) and to a lesser extent from mammoths (~5%). The African forest elephant ancestry was more closely related to modern West African forest elephants than to other African forest elephant populations. This hybridisation likely occurred in Africa, prior to migration of Palaeoloxodon into Eurasia,[16] and appears to be shared with other Palaeoloxodon species.[19]
Like other Eurasian Palaeoloxodon species, P. antiquus is believed to derive from the migration of a population of Palaeoloxodon recki out of Africa, suggested to have occurred around 800,000 years ago, approximately at the boundary between the Early Pleistocene and Middle Pleistocene. P. antiquus first appeared during the Middle Pleistocene, with the earliest record of Palaeoloxodon in Europe being from the Slivia site in Italy, dating to around 800-700,000 years ago.[20] Its earliest known appearance in northern Europe is in England around 600,000 years ago. The arrival of Palaeoloxodon in Europe coincided with the extinction of the temperate-adapted European mammoth species Mammuthus meridionalis and the migration of Mammuthus trogontherii (the steppe mammoth) into Europe from Asia.[21] The arrival of Palaeoloxodon in Europe was part of a larger faunal turnover event around the transition between the Early and Middle Pleistocene, where many European mammal species that characterised the preceding late Villafranchian became extinct, along with the dispersal of immigrant species into Europe from Asia and Africa.[22]
There appears to be no overlap between M. meridionalis and P. antiquus, which suggests that the latter might have outcompeted the former. During P. antiquus's hundreds of thousands of years of existence, its tooth morphology remained relatively static, unlike European mammoth populations.[21]
Skeletons of Palaeoloxodon falconeri a dwarf elephant species thought to have descended from the straight-tusked elephant native to Sicily and Malta
A number of species of dwarf elephants that are thought to have evolved from the straight-tusked elephant are known from many Mediterranean islands, spanning from Sicily and Malta in the west to Cyprus in the east. The responsible factors for the dwarfing of island mammals are thought to include the reduction in food availability, predation and competition from other herbivores.[23][24]
Palaeoloxodon antiquus is known from abundant finds across Europe, reaching its widest distribution on the continent during warm interglacial periods. Fossils are also known from Israel, western Iran[25] and probably Turkey[26] in West Asia. Some remains of the species have also been reported from Central Asia in northeastern Kazakhstan and Tajikistan.[25] Outside of Eastern Europe, the northernmost records of the species are known from Great Britain, Denmark and Poland, around the 55th parallel north.[27] Some of the northernmost reported fossils of the species are from the banks of the Kolva river in the Russian Urals at around the 60th parallel north. During glacial periodsP. antiquus permanently resided in the Mediterranean region.[25] Many of the West Asian remains have been assigned to the species primarily on the basis of geography, and it has been suggested that some of these, such as those from Israel, actually belong to P. recki.[28] A 2004 study attributed the holotype of Palaeoloxodon turkmenicus, a skull found in western Turkmenistan, to P. antiquus,[4] but later analysis found that P. turkmenicus represented a morphologically distinct and valid species.[20] The straight-tusked elephant is primarily associated with temperate and Mediterranean forest and woodland habitats, as opposed to the colder open steppe environments inhabited by contemporary mammoths,[29] though the species is also known to have inhabited open grasslands, and is thought to have been tolerant of a range of environmental conditions.[30]
As with modern elephants, female and juvenile straight-tusked elephants are thought to have lived in matriarchal herds of related individuals, with males leaving these groups to live solitarily upon reaching adolescence around 14–15 years of age.[8] Adult males likely engaged in combat with each other during musth similar to living elephants.[31] Some straight-tusked elephant specimens appear to document injuries obtained in fights with conspecifics; particularly notable specimens include a large male specimen from Neumark Nord that has a deep puncture hole wound in its forehead with surrounding bone growth indicating that it had healed, as well as another large male from the same locality with a healed puncture hole wound in its scapula.[32]
Like modern elephants, the herds would have been restricted to areas with available fresh water due to the greater hydration needs and lower mobility of the juveniles. Fossil tracks of newborns, calves and adults, which are likely of a herd of P. antiquus, have been found in dune deposits in southern Spain, dating to the early Late Pleistocene (Marine Isotope Stage (MIS) 5, around 130–80,000 years ago).[8] Due to their larger size, straight-tusked elephants are thought to have finished growing 10 to 15 years later than living elephants, continuing to grow after 50 years of age. They may also have lived longer than extant elephants, with lifespans perhaps in excess of 80 years.[3]
Dental microwear studies suggest that the diet of P. antiquus was highly variable, ranging from almost completely grazing to almost completely browsing (feeding on leaves, stems and fruits of high-growing plants). However, microwear only reflects the diet in the last few days or weeks before death, so the observed dietary variation may be seasonal,[33] as is the case with living elephants.[30] Isotopic analysis of a specimen from Greece suggests that it was primarily browsing during the dry (presumably summer) months and consumed more grass during the wet (presumably winter) months.[30] Dental mesowear analysis suggests that the diet also varied according to local environmental conditions, with individuals occupying more grass-dominated open environments having a greater grazing-related wear signal.[34] Preserved stomach contents of German specimens found at Neumark Nord suggests that in temperate Europe, its diet included trees such as maple, linden/lime, hornbeam, hazel, alder, beech, ash, oak, elm, spruce and possibly juniper, as well as other plants like ivy, Pyracantha, Artemisia,mistletoe (Viscum), thistles (Carduus and Cirsium), grass and sedges (Carex), as well as members of Apiaceae, Lauraceae, Rosaceae, Caryophyllaceae and Asteraceae (including the subfamily Lactuceae).[35]
Straight-tusked elephants rarely coexisted alongside mammoths, although they occasionally did so, like at the Ilford locality in Britain that dates to the Marine Isotope Stage (MIS) 7 interglacial (~200,000 years ago) and where both steppe mammoths and P. antiquus are found. At this locality, the two species appear to have engaged in dietary niche partitioning.[5]
A Middle Pleistocene landscape in Spain, including a straight-tusked elephant (background centre-left) as well as the extinct fallow deer Dama ceciliae (foreground) wild horse (left), bison, (background centre) aurochs (background right) and the narrow-nosed rhinoceros (far right)
Potential gnaw marks suggested to have been made by hyenas and lions on the bones of straight-tusked elephants have been reported at some localities, which suggests that these species likely at least scavenged on the remains of straight-tusked elephants like lions and hyenas do on elephants in Africa today.[40] Remains of juvenile straight-tusked elephants are also known from Kirkdale Cave in northern England, a well known cave hyena den.[41]
Relationship with humans
Remains of straight-tusked elephants at numerous sites are associated with stone tools and/or bear cut and percussion marks indicative of butchery. At most sites it is unclear whether the elephants were hunted or scavenged, though both scavenging of already dead elephants and active hunting are likely to have occurred.[42][31] Straight-tusked elephant butchery sites have been found in Israel,[a] Spain,[b] Italy,[c] Greece,[d] Britain,[e] and Germany.[f]
These sites are likely attributable to Homo heidelbergensis and Neanderthals.[31] Stone tools used at these sites include flakes, choppers, bifacial tools like handaxes, as well as cores.[31] At some sites, the bones of straight-tusked elephants[53] and in at least one case their ivory[60] were used to make tools. There is evidence that exploitation of straight-tusked elephants in Europe increased and became more systematic from the mid-Middle Pleistocene (around 500,000 years ago) onwards.[31][58] Based on analysis of sites of straight-tusked elephants with cut marks and/or artifacts, it has been argued that there is little evidence that straight-tusked elephants were targeted preferentially over smaller animals.[31] Most individuals at these sites are subadult to adult and primarily male in sex. The male sex bias likely both represents the fact that adult males, despite their larger size, were more vulnerable targets due to their solitary nature, as well as the tendency of adult male elephants to engage in risky behavior causing them to more frequently die in natural traps, as well as being weakened or killed by injuries caused by combat with other male elephants during musth.[31]
At the Lehringen site in north Germany, dating to the Eemian/Last Interglacial (around 130-115,000 years ago) a skeleton of P. antiquus was found with a spear made of yew wood between its ribs, with flint artifacts found close by, providing unequivocal evidence that this specimen was hunted[59][42] (though the elephant may have already been mired prior to being killed[61]). Studies in 2023 proposed that in addition to Lehringen, the Neumark Nord, Taubach and Gröbern sites, which show evidence of systematic butchery, provided evidence of widespread hunting of straight-tusked elephants by Neanderthals during the Eemian in Germany.[42][58] The remains of at least 57 elephants were found at Neumark Nord; the study authors estimated that they accumulated over a time span of around 300 years and that one elephant was hunted once every 5–6 years at the site.[42]
A straight-tusked elephant tibia with deliberate human made incisions, from the Bilzingsleben site in Germany
At the Bilzingsleben site in Germany and the Stránská Skála 1 site in the Czech Republic, bones of straight-tusked elephants have been found engraved with roughly parallel lines of unclear purpose.[62]
There are no cave paintings that unambiguously depict P. antiquus. An outline drawing of an elephant in El Castillo cave in Cantabria, Spain, as well as a drawing from Vermelhosa in Portugal have been suggested to possibly depict it, but these could also potentially depict woolly mammoths.[29][63]
Palaeoloxodon antiquus retreated from northern Europe after the end of the Eemian interglacial around 115,000 years ago due to climatic conditions becoming unfavourable, and fossils after that time during the Last Glacial Period are rare. A molar from the cave deposits of Grotta Guattari in central Italy has been suggested to date to around 57,000 years ago, though other studies have found it to have an older early Late Pleistocene age,[64] and later dating done in 2023 suggested an age of deposition in the cave of around 66–65,000 years ago.[65][66] Another late Italian record has been reported from Mousterian layers in Barma Grande cave in northwest Italy, probably dating to around the same time as Grotta Guattari, which has been suggested to display evidence of butchery by Neanderthals.[60] Other late remains have been reported from several sites in the Iberian Peninsula,[64][29] including El Castillo cave in northern Spain, which were initially radiocarbon dated to 43,000 years ago,[29] with later calibration suggesting an age of around 49,570–44,250 years Before Present,[67] and Foz do Enxarrique (a sequence of terrace deposits of the Tagus river) in central-eastern Portugal, originally dated to around 34–33,000 years ago,[29] but later revised to around 44,000 years ago.[68] A late date of around 37,400 years ago has been reported from a single molar found in the North Sea off the coast of the Netherlands,[69] but it has been suggested that this date needs independent confirmation, due to only representing a single sample.[70] Some authors have suggested that P. antiquus likely survived until around 28,000 years ago in the southern Iberian Peninsula based on footprints found in Southwest Portugal[71] and Gibraltar.[72] While some authors have argued that climate change was primarily responsible for the extinction of the straight-tusked elephant,[71] others have argued that climate change alone cannot account for the species extinction.[64] Human hunting has been suggested to have possibly played a contributory role, but the importance of this is uncertain.[71][64]
The extinction was part of the Late Pleistocene megafauna extinctions, which resulted in the extinction of most large terrestrial mammals globally. The extinction of P. antiquus and other temperate adapted European megafauna has resulted in a severe loss of functional diversity in European ecosystems.[36]
Notes
^Revadim Quarry[43] (sometime between 780,000 and 300–500,000 years ago [44]) Gesher Benot Ya'akov[45] dating to around 780,000 years ago formerly attibuted to P. antiquus is now attributed to P. recki[4][20]
^including Ambrona AS3,[46] dating to MIS 12 c. 478-425,000 years ago, Aridos 1, dating to MIS 11-9 around 424-300,000 years ago & Aridos 2,[47] dating to MIS 11 c. 425-375,000 years ago
^including Notarchirico[48] dating to c. 670-610 ,000 years ago,[44] (though the evidence for butchery at this site is disputed[49]), Ficoncella[50] dating to c. 500,000 years ago, Castel di Guido[51][52][53] dating to 400,000 years ago,[53] La Polledrara di Cecanibbio c. 325–310,000 years ago[44] and Poggetti Vecchi c. 171,000 years ago[54]
^the Marathousa 1 site dating to c. 500-400,000 years ago[55]
^the Ebbsfleet elephant site, dating to c. 425-375,000 years ago[56]
^including Schöningen, dating to c. 300,000 years ago[57] Gröbern[42][58] Taubach[58] Lehringen[59][42] and Neumark Nord,[42] the latter of which date to the Eemian (Last) interglacial, approximately 130-115,000 years ago[42][58]
References
^Benoit, J., Legendre, L. J., Tabuce, R., Obada, T., Mararescul, V., & Manger, P. (2019). Brain evolution in Proboscidea (Mammalia, Afrotheria) across the Cenozoic. Scientific Reports, 9(1), 9323. https://doi.org/10.1038/s41598-019-45888-4
^ abEleftheria Palkopoulou; Mark Lipson; Swapan Mallick; Svend Nielsen; Nadin Rohland; Sina Baleka; Emil Karpinski; Atma M. Ivancevic; Thu-Hien To; R. Daniel Kortschak; Joy M. Raison; Zhipeng Qu; Tat-Jun Chin; Kurt W. Alt; Stefan Claesson; Love Dalén; Ross D. E. MacPhee; Harald Meller; Alfred L. Roca; Oliver A. Ryder; David Heiman; Sarah Young; Matthew Breen; Christina Williams; Bronwen L. Aken; Magali Ruffier; Elinor Karlsson; Jeremy Johnson; Federica Di Palma; Jessica Alfoldi; David L. Adelson; Thomas Mailund; Kasper Munch; Kerstin Lindblad-Toh; Michael Hofreiter; Hendrik Poinar; David Reich (2018). "A comprehensive genomic history of extinct and living elephants". Proceedings of the National Academy of Sciences of the United States of America. 115 (11): E2566–E2574. Bibcode:2018PNAS..115E2566P. doi:10.1073/pnas.1720554115. PMC5856550. PMID29483247.
^MR Palombo, E Albayrak, F Marano (2010) The straight-tusked Elephants from Neumark Nord, a glance to a lost world. In: Meller H (ed) Elefantenreich—eine Fossilwelt in Europa. Archäologie in Sachsen-Anhalt, Sonderband, Halle-Saale, pp 219–247 (p. 237 for relevant content)
^Grube, R., Palombo, M., Iacumin, P. & Di Matteo, A. What did the fossil elephants from Neumark–Nord eat? In Elefantenreich – Eine Fossilwelt in Europa. (ed. Meller, H.) 253–272 (Landesamt für Denkmalpflege und Archäologie Sachsen-Anhalt, 2010). (p. 258 for relevant content)
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