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Proboscidea

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Proboscidea is a taxonomic order of mammals that includes modern elephants and many of their extinct relatives.

African elephant (PSF)
African elephant (PSF)

This group belongs to a larger group of mammals called Afrotheria. It includes the three living species we recognize today: the African bush elephant, the African forest elephant, and the Asian elephant. Beyond living species, the order contains many extinct families like the deinotheres, mastodons, and gomphotheres. Some members of this order were among the largest land mammals to ever exist.

Mammut borsoni from Milia
Mammut borsoni from Milia

The elephant Palaeoloxodon namadicus and the mastodon Mammut borsoni were massive. These animals may have had body masses that rivaled or even exceeded the paraceratheres. The largest living member is the African bush elephant. It can reach a shoulder height of 4 meters and weigh 10.4 tonnes.

Evolutionary changes in Proboscidea involved a massive increase in body size. This growth likely helped them survive by allowing them to eat vegetation with low nutritional value. As they grew, their physical structures changed to support their weight. Their limbs became longer, while their feet became shorter and broader. They transitioned from a plantigrade stance to a digitigrade stance. This means they walked on their toes. To support this, they developed cushion pads and used the sesamoid bone for stability. The skull also grew larger, particularly the cranium. To help hold up this heavy skull, the neck became shorter.

Palaeoloxodon antiquus size comparison
Palaeoloxodon antiquus size comparison

One of the most famous features of later proboscideans is the trunk. The trunk is a long, muscular organ used for reaching food. This developed as the nasal regions of the skull retracted. Another major feature is the tusks. These are large teeth primarily made of dentine. In some groups, like the Elephantiformes, the second upper and lower incisors transformed into ever-growing tusks. In the Deinotheriidae family, tusks only appeared on the lower jaw.

Deinotherium12
Deinotherium12

The size of these tusks varied greatly. A mammoth tusk could weigh over 100 kilograms. Some primitive species, like Stegotetrabelodon, had lower tusks reaching 2.5 meters in length.

Teeth also underwent significant specialization. In the group known as Elephantimorpha, molar teeth were replaced horizontally rather than vertically. This is different from how most other mammals replace their teeth. Members of the family Elephantidae developed a specific type of tooth called hypsodont teeth. These are high-crowned teeth with parallel lophs, which are ridges on the tooth surface. This specialized shape made them much more efficient at grazing on grass. This change helped them adapt as their diets shifted from browsing on leaves to grazing on grass.

Moeritherium NT crop
Moeritherium NT crop

The history of Proboscidea began in Africa during the Paleocene epoch. The earliest known member, Eritherium, lived about 60 million years ago. It was very small, with a mass of only about 20 kilograms. By the late Eocene, Barytherium had grown to about 2 tonnes. Some early members, like Moeritherium, were likely semi-aquatic. A major turning point occurred during the Early Miocene, about 18 to 19 million years ago. The collision of Afro-Arabia with Eurasia allowed proboscideans to spread from Africa into Eurasia. Later, they moved into North America via the Bering Land Bridge.

Mammuthus meridionalis reconstruction 2
Mammuthus meridionalis reconstruction 2

Different groups dominated at different times. During the Miocene, groups like gomphotheres and amebelodontids were prominent. Around 10 million years ago, the first members of the family Elephantidae emerged in Africa from gomphotheres. During the Pleistocene, many non-elephantid groups went extinct. However, some species experienced insular dwarfism. This happened when populations became isolated on islands. Due to limited resources and fewer predators, they evolved to be much smaller. For example, the dwarf elephant Elephas falconeri was only about 1 meter tall.

Palaeoloxodon falconeri Size Comparison
Palaeoloxodon falconeri Size Comparison
202003 Woolly mammoth
202003 Woolly mammoth

Many proboscideans lived in social groups. Scientists believe the American mastodon lived in herds similar to modern elephants. These herds likely consisted of females and juveniles, while adult males lived alone. It is also thought that they communicated using infrasound. This is sound that is too low for humans to hear. While most non-elephantid groups died out during the Late Pleistocene, some mammoths survived on islands. A population of woolly mammoths lived on Wrangel Island until approximately 4,000 years ago.

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🖼️ Images & Media (19)
Phosphatherium - head restoration.tif
File:Numidotherium koholense skull.png
Numidotherium koholense skull.png
File:Moeritherium NT crop.jpg
Moeritherium NT crop.jpg
File:Deinotherium12.jpg
Deinotherium12.jpg
File:Palaeomastodon NT small.jpg
Palaeomastodon NT small.jpg
File:Mammut americanum.png
Mammut americanum.png
File:Mammut borsoni from Milia.jpg
Mammut borsoni from Milia.jpg
File:Gomphotherium NT small (flipped).jpg
Gomphotherium NT small (flipped).jpg
File:Cuvieronius hyodon2.jpg
Cuvieronius hyodon2.jpg
File:Stegomastodon sp.png
Stegomastodon sp.png
File:Stegodon ganesaDB.jpg
Stegodon ganesaDB.jpg
File:Mammuthus meridionalis reconstruction 2.jpg
Mammuthus meridionalis reconstruction 2.jpg

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