Английская Википедия:Anancus

Содержание

Текст

Текст

Текст

Текст

Текст

Текст

Текст

Текст

Текст

Anancus is an extinct genus of "tetralophodont gomphothere" native to Afro-Eurasia, that lived from the Tortonian stage of the late Miocene until its extinction during the Early Pleistocene, roughly from 8.5–2 million years ago.

Taxonomy

Anancus was named by Auguste Aymard in 1855. It is traditionally allocated to Gomphotheriidae, often as the only member of the subfamily Anancinae. Recently, some authors have excluded Anancus along with other tetralophodont gomphotheres from Gomphotheriidae, and regarded them as members of Elephantoidea instead.

Description

Файл:Anancus NT small.jpg

Anancus arvernensis

Файл:Anancus skull.png

Skull of Anancus sivalensis in side view

Two largely complete individuals of Anancus arvernensis reached shoulder heights of around Шаблон:Convert, with a volumetric estimate suggesting a body mass of around 5.2 to 6 tons, comparable to living African elephants. The tusks were largely straight and lacked enamel (though enamel was present in juveniles) and were slender, and proportionally large, with a large tusk of the species Anancus avernensis from Stoina, Romania measuring Шаблон:Convert in length with an estimated mass of Шаблон:Convert. The tusks varied from projecting forward parallel to each other, to being outwardly divergent from each other, depending on the species. The skull is proportionally tall and short, with an elevated dome and an enlarged tympanic bulla. Unlike more primitive gomphotheres, the mandible was brevirostrine (shortened), and lacked lower tusks. The molars were typically tetralophodont (bearing four crests or ridges) but were pentalophodont in some species. The premolars were absent in all species other than A. kenyensis. On the upper molars, the posterior pretrite central conules were reduced, as were the anterior pretrite central conules on the lower molars. The pretrite and posttrite half-loph(id)s were dislocated from each other, resulting in the successive loph(id)s exhibiting an alternating pattern.

Diet

Dietary preferences of Anancus varied between species. Dental microwear analysis of Anancus arvernensis specimens from the Early Pleistocene of Europe generally suggests that it was a browser, consuming twigs, bark, seeds and fruit, with a browsing diet also proposed for the Early Pliocene South African A. capensis. The East African late Miocene-early Pliocene A. kenyensis and Pliocene A. ultimus have individuals with varying browsing, grazing, and mixed feeding (both browsing and grazing) diets, with a grazing diet proposed for Anancus specimens from the Pliocene of India based on isotopic analysis. Anancus osiris from the Pliocene of North Africa is suggested to have been a mixed feeder with a large grass intake based on microwear.

Evolution

Anancus is suggested to have evolved from Tetralophodon or a Tetralophodon-like ancestor. The oldest known species of Anancus is A. perimensis, with fossils known from the Tortonian ~ 8.5 million years ago Siwalik Hills of Pakistan. Anancus entered Europe approximately 7.2 million years ago and around 7 million years ago dispersed into Africa. Anancus first appeared in China around 6 million years ago (A. sinensis). Anancus disappeared from Asia and Africa around the end of the Pliocene, approximately 2.6 million years ago. The extinction of Anancus in Africa has been attributed to competitive exclusion by elephantids, whose molar teeth were more efficient at processing grass. The European A. arvernensis was the last surviving species, becoming extinct during the Early Pleistocene, around 2 million years ago, with its latest possible record being at Eastern Scheldt in the Netherlands around 1.6 million years ago.

Gallery

• The jaw of Anancus, an extinct relative of the elephant

  The jaw of Anancus, an extinct relative of the elephant

• Jaw of Anancus arvernensis from Quaternary of Italy

  Jaw of Anancus arvernensis from Quaternary of Italy

• Molar of Anancus arvernensis

  Molar of Anancus arvernensis

References

• Шаблон:Cite book