The West Runton mammoth (Mammuthus trogontherii) and its evolutionary significance

The West Runton mammoth (WRM) is one of the best-stratified, most complete and best-preserved skeletons of the so-called 'steppe mammoth', Mammuthus trogontherii. The skeleton was a male of estimated age 41 years at death. Its estimated live shoulder height of 3.9 m, and body mass of around 9 tonnes, are typical for males of the species. Together with other European skeletons, the WRM indicates a similar body size for Mammuthus meridionalis and M. trogontherii. The WRM, dating from the early part of the early Middle Pleistocene (c. 700 ka), represents an important marker in European mammoth evolution. In its mandible and dentition it has a clearly 'advanced' morphology overall, similar to most M. trogontherii and Mammuthus primigenius, and unlike most M. meridionalis. In its molar morphology in particular (especially plate number), the WRM already falls in the upper end of the range seen in later samples of M. trogontherii, such as those from Süssenborn and Mosbach. This early appearance of a dentally advanced mammoth runs counter to the gradualistic model of European mammoth evolution but is consistent with immigration of M. trogontherii from Asia. The WRM is more advanced than the meridionalis/trogontherii 'mosaic' mammoths from Voigtstedt, but previously-collected molars from West Runton hint at possible meridionalis or mosaic individuals there too.