Straight-tusked elephant
The straight-tusked elephant 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 and a weight of, placing them among the largest land mammals ever. 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, when northern Europe was occupied by steppe mammoths and later woolly mammoths. Skeletons found in association with stone tools and in one case, a wooden spear, suggest they were scavenged and hunted by early humans, including Homo heidelbergensis and their Neanderthal successors.
The species is part of the genus Palaeoloxodon, 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, around the time of the extinction of the previously dominant mammoth species Mammuthus meridionalis. The straight-tusked elephant is the ancestor of over half a dozen named species of dwarf elephants that inhabited islands in the Mediterranean, some of which shrunk to only 2% the size of their mainland ancestor. The straight-tusked elephant 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.
Description
Anatomy
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.The skull is proportionally both very wide and tall. 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, with the crest being more pronounced in older individuals, as well as due to distortion during fossilisation. 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. The premaxillary bones 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. The teeth are high crowned, with each third molar having approximately 16–21 lamellae.
Size
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 and a weight between. 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 and masses between. Extremely large bulls, such as those represented by a now lost pelvis and tibia collected from the Iberian Peninsula in the 19th century, may have reached shoulder heights of and body masses of over, exceeding the body mass estimated for the largest specimens of Paraceratherium transouralicum, the otherwise largest known land mammal. Adult males had tusks typically around long, with masses comfortably exceeding. The preserved portion of one particularly large and thick tusk from Aniene, Italy, is in length, has a circumference of around where it would have exited the skull, and is estimated to have weighed over in life.Females were considerably larger than living female elephants and comparable in size with African bush elephant bulls, with female individuals from the Neumark Nord population in Germany reaching shoulder heights and weights rarely exceeding and respectively. A particularly large female known from a pelvis found near Binsfeld in Germany has been estimated to have had a shoulder height of and a weight of. For comparison, 90% of fully grown female African bush elephants reach an shoulder height of and body mass of under optimal growth conditions. Newborn and young calves were likely around the same size as those of modern elephants. A largely complete 5 year old calf from Cova del Rinoceront in Spain was estimated to have a shoulder height of and a body mass of, which is comparable to a similarly aged African bush elephant.
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 by some 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.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 declared to be purely mineral in nature by the Collegium Medicum in the nearby city of Gotha, this was disputed by Wilhelm Ernst Tentzel, a polymath in the employ of the ducal court of Saxe-Gotha-Altenburg, who correctly identified them as elephant remains, which he assumed were deposited by the biblical deluge. The controversy became the subject of widespread discussion among contemporary scholars in Europe. A century later, the Burgtonna skeleton was one of the specimens on which Johann Friedrich Blumenbach based his description of the woolly mammoth in his publication naming the species in 1799. The remains of straight-tusked elephants continued to be attributed to woolly mammoths until the 1840s.40
The straight-tusked elephant was scientifically named in 1847 by British palaeontologists Hugh Falconer and Proby Cautley as Elephas ''antiquus.40-41 The type specimen is a mandible with a second molar. The exact provenance of the specimen is unknown, though it probably originates from Britain, and possibly the site of Grays in Essex, southeast England. This specimen was originally considered to be that of a mammoth, and the attribution to E. antiquus was made in a hand-written correction.40 The common name "straight-tusked elephant" was used for the species as early as 1873 by William Boyd Dawkins. In 1924, the Japanese paleontologist Matsumoto Hikoshichirō assigned E. antiquus to his new taxon Palaeoloxodon, which he classified as a subgenus of Loxodonta.40 The species has a confused taxonomic history, with at least 21 named synonyms.41 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.42 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. While the sinking of Palaeoloxodon into Elephas gained considerable traction in the following decades, today both P. antiquus and Palaeoloxodon'' are considered distinct.