A new Mammutidae (Proboscidea, Mammalia) from the Late Miocene of Gansu Province, China

Abstract

The "Yanghecun specimen", a proboscidean specimen represented by a mandible from Miocene of China and previously described as Gomphotheriidae, is here reviewed and described as a new genus and species of Mammutidae: Sinomammut tobieni. This taxon is a longirostrine mastodon, lacking lower tusks, and bearing a wide last molar with oblique and non-infl ated lophids, broad transverse interlophids, and yoke-like wear fi gures. Phylogenetic analysis of Mammutidae based on dental and mandibular features recovered S. tobieni as sister group of the mastodon Mammut. The longirostrine condition and the well-developed lower incisors seem to be primitive for Mammutidae, while the brevirostry is the derived condition, probably emerged during the middle Miocene (12-11 Mya). However, two derived conditions are recognized to the lower tusks: the absence of lower tusks (S. tobieni) and the occasional presence of vestigial lower tusks (Mammut).

The Dance of Tusks: Rediscovery of Lower Incisors in the Pan-American Proboscidean Cuvieronius hyodon Revises Incisor Evolution in Elephantimorpha

“…The brevirostrine condition of mandible occurred independently of (and later than) the loss of lower incisors ( Fig 3 ). The association of longirostrine and tuskless mandibles is very rare in proboscideans, and only Choerolophodon (family Choerolophodontidae, sensu [ 23 ]), a recently described new genus of Mammutidae [ 44 ], as well as the non-amebelodontine trilophodont gomphotheres Gnathabelodon and Eubelodon show these two conditions simultaneously. Moreover, the emergence of brevirostry in Clade B appears to be related to a more open environment, the Savanna ( Fig 3 ), which is in accordance with previous studies [ 6 ].…”

“…Accordingly, the Miocene epoch is known by its climatic instability [ 50 ] and climatic fluctuations are one of the best candidates to promote such evolutionary selections ( Fig 5 ). The climatic variations in global temperature and humidity throughout the Miocene, the "Zachos Curve” [ 50 ], is compared to a time-calibrated phylogenetic hypothesis for Elephantimorpha [ 6 , 23 , 44 , 49 ], most of the rapid cooling/drought events (E1, E2 and E3) coincides with the loss of lower incisors in distinct lineages of Elephantimorpha ( Fig 5 ).…”

A partial skeleton of “Mammut” borsoni (Proboscidea, Mammalia) from the Pliocene of Kaltensundheim (Germany)

“…In any case, a sexual differentiation has to be considered when discussing Miocene Mammutidae. Therefore, some of the described taxa based on tuskless mandibles, e.g., Pliomastodon furlongi Shotwell and Russel, 1963 from Oregon or Sinomammut tobieni Mothé, et al, 2016 from China have to be reconsidered.…”

“…Several other mammutid species and genera preceding "M". borsoni were described from the Neogene of Europe (e.g., Nikolov and Kovačev, 1966;Kubiak, 1972;Markov 2004Markov , 2008 and Asia (e.g., Mothé et al, 2016;Wang et al, 2020;Zhang and Wang, 2021). For several of these species the taxonomic identity and validity is, however, under debate, because of incomplete materials that provide only a limited number of characters.…”