Anancus was named by Auguste Aymard in 1855. It is traditionally allocated to Gomphotheriidae, often as the only member of the subfamily Anancinae.[1][2] Recently, some authors have excluded Anancus along with other tetralophodont gomphotheres from Gomphotheriidae, and regarded them as members of Elephantoidea instead.[3][4][5]
Description
Anancus arvernensisSkull of Anancus sivalensis in side view
Two largely complete individuals of Anancus arvernensis reached shoulder heights of around 2.5–2.6 metres (8 ft 2 in – 8 ft 6 in), with a volumetric estimate suggesting a body mass of around 5.2 to 6 tonnes (11,000 to 13,000 lb), comparable to living African bush elephants.[6] The tusks were largely straight and lacked enamel[6] (though enamel was present in juveniles[7]) and were slender,[8] and proportionally large, with a large tusk of the species Anancus avernensis from Stoina, Romania measuring 3.71 metres (12.2 ft) in length with an estimated mass of 70 kilograms (150 lb).[9] The tusks varied from projecting forward parallel to each other, to being outwardly divergent from each other, depending on the species.[10] 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.[11]
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,[12] with a browsing diet also proposed for the Early Pliocene South African A.capensis.[13] 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,[14][15] with a grazing diet proposed for Anancus specimens from the Pliocene of India based on isotopic analysis.[16]Anancus osiris from the Pliocene of North Africa is suggested to have been a mixed feeder with a large grass intake based on microwear.[17]
Evolution
Anancus is suggested to have evolved from Tetralophodon or a Tetralophodon-like ancestor.[8][6] 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.[11] The extinction of Anancus in Africa has been attributed to competitive exclusion by elephantids, whose molar teeth were more efficient at processing grass.[14][18] The European A. arvernensis was the last surviving species, becoming extinct during the Early Pleistocene, around 2 million years ago,[11] with its latest possible record being at Eastern Scheldt in the Netherlands around 1.6 million years ago.[12]
Gallery
The jaw of Anancus, an extinct relative of the elephant
Jaw of Anancus arvernensis from Quaternary of Italy
Molar of Anancus arvernensis
References
^Hautier, Lionel; Mackaye, Hassane Taisso; Lihoreau, Fabrice; Tassy, Pascal; Vignaud, Patrick; Brunet, Michel (March 2009). "New material of Anancus kenyensis (proboscidea, mammalia) from Toros-Menalla (Late Miocene, Chad): Contribution to the systematics of African anancines". Journal of African Earth Sciences. 53 (4–5): 171–176. Bibcode:2009JAfES..53..171H. doi:10.1016/j.jafrearsci.2009.01.003.
^Shoshani, J.; Tassy, P. (1996). "Summary, conclusions, and a glimpse into the future". In Shoshani, Jeheskel; Tassy, Pascal (eds.). The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives. Oxford University Press. pp. 335–348. ISBN978-0-19-854652-8.
^Theodorou, G., Spjeldnaes, N., Hanken, N. M., Lauritzen, S. E., Velitzelos, E., Athanassiou, A., et al. (2000). Description and taphonomic investigations of Neogene Proboscidea from Rhodos, Greece. Annales Géologiques des Pays Helléniques, 38, 133–156.
