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
The
type species,
Anancus arvernensis, was originally named in 1828 by Jean-Baptiste Croizet and Antoine Claude Gabriel Jobert as
Mastodon arvernensis, based on remains found within the vicinity of the Puy de Dôme volcano in the
Massif Central in central southern France, with the species name deriving from the
Auvergne region of France where it was found.
[Croizet, J. B., and A. C. G. Jobert. 1828. Recherches sur les ossemens fossiles du département du Puy-de-Dôme. Principaux Libraries, Paris, 226 pp.] Anancus was subsequently named by
Auguste Aymard in 1855 in a publication by M. J. Dorlhac, also based on remains found in the Massif Central region.
[Dorlhac, M. J. 1855. Notice géologique sur le cratère de Coupet et sur son gisement de gemmes et d'ossements fossiles. Annales de la Société d'agriculture, sciences, arts et commerce du Puy 19:497–517.] The genus name
Anancus derives from the Latin word
ancus meaning "bent/curved" and the negative prefix "an-" with the intended meaning of "uncurved, straight" in reference to the shape of the tusks.
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
Two largely complete individuals of
Anancus arvernensis reached shoulder heights of around , with a volumetric estimate suggesting a body mass of around , comparable to living African bush elephants.
The tusks were largely straight and lacked enamel
(though enamel was present in juveniles
[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.]) and were slender,
and proportionally large, with a large tusk of the species
Anancus avernensis from
Stoina, Romania measuring in length with an estimated mass of .
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 skull of
Anancus species is very similar to living elephants and like them they probably had free-hanging (pendulous) trunks.
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 and ecology
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.
from the Pliocene of North Africa is suggested to have been a mixed feeder with a large grass intake based on microwear.
Anancus often coexisted alongside other proboscideans, such as the larger mastodon "Mammut" borsoni in Pliocene Europe.
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
Sivalik 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
Elephantidae, 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
File: Anancus jaw.JPG| The jaw of Anancus, an extinct relative of the elephant
File: Gomphotheriidae - Anancus arvernensis-000.JPG|Jaw of Anancus arvernensis from Quaternary of Italy
File:Anancus arvernensis .JPG|Molar of Anancus arvernensis
