Product Code Database
Proboscidea (; , ) is a taxonomic order of Afrotheria paenungulate mammals described by J. Illiger in 1811. It encompasses the Elephant (family Elephantidae) and their extinct relatives. Three living species of elephant are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant.
Extinct members of Proboscidea include the Deinotheriidae, Mastodon, Gomphothere, Amebelodontidae and Stegodon. The family Elephantidae also contains several extinct groups, including and Palaeoloxodon. Proboscideans include some of the largest known land mammals, with the elephant Palaeoloxodon namadicus and mastodon "Mammut" borsoni suggested to have body masses surpassing , rivalling or exceeding paraceratheres, the otherwise largest known land mammals in size. The largest living proboscidean is the African bush elephant, with a recorded maximum size of 4 meters (13.1 feet) at the shoulder and a weight of 10.4 tonnes (11.5 short tons). In addition to their enormous size, later proboscideans are distinguished by tusks and long, muscular trunks, which were less developed or absent in early proboscideans.
A major event in proboscidean evolution was the collision of Afro-Arabia with Eurasia, during the Early Miocene, around 18-19 million years ago allowing proboscideans to disperse from their African homeland across Eurasia, and later, around 16-15 million years ago into North America across the Bering Land Bridge. Proboscidean groups prominent during the Miocene include the , along with the more advanced Elephantimorpha, including Mammutidae (mastodons), , Amebelodontidae (which includes the "shovel tuskers" like Platybelodon), choerolophodontids and Stegodontidae. Around 10 million years ago, the earliest members of the family Elephantidae emerged in Africa, having originated from gomphotheres.H. Saegusa, H. Nakaya, Y. Kunimatsu, M. Nakatsukasa, H. Tsujikawa, Y. Sawada, M. Saneyoshi, T. Sakai Earliest elephantid remains from the late Miocene locality, Nakali, Kenya Scientific Annals, School of Geology, Aristotle University of Thessaloniki, Greece VIth International Conference on Mammoths and Their Relatives, vol. 102, Grevena -Siatista, special volume (2014), p. 175 The Late Miocene saw major climatic changes, which resulted in the decline and extinction of many proboscidean groups such as amebelodontids and choerolophodontids. The earliest members of modern genera of Elephantidae appeared during the latest Miocene-early Pliocene around 6-5 million years ago. The elephantid genera Elephas (which includes the living Asian elephant) and Mammuthus (mammoths) migrated out of Africa during the late Pliocene, around 3.6 to 3.2 million years ago.
Over the course of the Early Pleistocene, all non-elephantid probobscideans outside of the Americas became extinct (including mammutids, gomphotheres and deinotheres), with the exception of Stegodon. Gomphotheres dispersed into South America during this era as part of the Great American interchange, and mammoths migrating into North America around 1.5 million years ago. At the end of the Early Pleistocene, around 800,000 years ago the elephantid genus Palaeoloxodon dispersed outside of Africa, becoming widely distributed in Eurasia. By the beginning of the Late Pleistocene, proboscideans were represented by around 23 species. Proboscideans underwent a dramatic decline during the Late Pleistocene as part of the Late Pleistocene megafauna extinctions, with all remaining non-elephantid proboscideans (including Stegodon, , and the American gomphotheres Cuvieronius and Notiomastodon) and Palaeoloxodon becoming extinct, with mammoths only surviving in relict populations on islands around the Bering Strait into the Holocene, with their latest survival being on Wrangel Island around 4,000 years ago.
The following cladogram is based on endocasts.
The skull grew larger, especially the cranium, while the neck shortened to provide better support for the skull. The increase in size led to the development and elongation of the mobile trunk to provide reach. The number of , incisors and Canine tooth decreased. The cheek teeth (molars and premolars) became larger and more specialised. In Elephantiformes, the second upper incisor and lower incisor were transformed into ever growing on the upper and lower jaws, while in Deinotheriidae there are only tusks on the lower jaw. The tusks are proportionally heavy for their size, being primarily composed of dentine. In primitive proboscideans, a band of enamel covers part of the tusk surface, though in many later groups including modern elephants the band is lost, with elephants only having enamel on the tusk tips of juveniles. The upper tusks were initially modest in size, but from the Late Miocene onwards proboscideans developed increasingly large tusks, with the longest ever recorded tusk being long belonging to the mammutid "Mammut" borsoni found in Greece, with some mammoth tusks likely weighing over . The lower tusks are generally smaller than the upper tusks, but could grow to large sizes in some species, like in Deinotherium (which lacks upper tusks), where they could grow over long, the Amebelodontidae Konobelodon has lower tusks long, with the longest lower tusks ever recorded being from the primitive elephantid Stegotetrabelodon which are around long.
The molar teeth changed from being replaced vertically as in other mammals to being replaced horizontally in the clade Elephantimorpha. While early Elephantimorpha generally had lower jaws with an elongated mandibular symphysis at the front of the jaw with well developed lower tusks/incisors, from the Late Miocene onwards, many groups convergently developed brevirostrine (shortened) lower jaws with vestigial or no lower tusks. Elephantids are distinguished from other proboscideans by a major shift in the molar morphology to parallel lophs rather than the cusps of earlier proboscideans, allowing them to become higher crowned (hypsodont) and more efficient in consuming grass.
Elephas celebensis of Sulawesi is believed to have descended from Elephas planifrons. Elephas falconeri of Malta and Sicily was only , and had probably evolved from the straight-tusked elephant. Other descendants of the straight-tusked elephant existed in Cyprus. Dwarf elephants of uncertain descent lived in Crete, Cyclades and Dodecanese, while dwarf mammoths are known to have lived in Sardinia.Sukumar, pp. 31–33. The Columbian mammoth colonised the Channel Islands and evolved into the pygmy mammoth. This species reached a height of and weighed . A population of small woolly mammoths survived on Wrangel Island as recently as 4,000 years ago. After their discovery in 1993, they were considered dwarf mammoths. This classification has been re-evaluated and since the Second International Mammoth Conference in 1999, these animals are no longer considered to be true "dwarf mammoths".
Ecology
It has been suggested that members of Elephantimorpha, including mammutids, gomphotheres, and stegodontids, lived in herds like modern elephants. Analysis of remains of the American mastodon ( Mammut americanum) suggest that like modern elephants, that herds consisted of females and juveniles and that adult males lived solitarily or in small groups, and that adult males periodically engaged in fights with other males during periods similar to musth found in living elephants. These traits are suggested to be inherited from the last common ancestor of elephantimorphs, with musth-like behaviour also suggested to have occurred in gomphotheres. All elephantimorphs are suggested to have been capable of communication via infrasound, as found in living elephants. Deinotheres may have also lived in herds, based on tracks found in the Late Miocene of Romania. Over the course of the Neogene and Pleistocene, various members of Elephantida shifted from a browse-dominated diet towards mixed feeding or grazing.
Classification
Below is a taxonomy of proboscidean genera as of 2019.
Bibliography
|
|
