Het Gat: preliminary note on a Bavelian fauna from the North Sea with possibly two mammoth species

We describe the fossil vertebrate remains from a site (‘Het Gat’) on the bottom of the North Sea, between the United Kingdom and the Netherlands. The site is a maximally c. 46 m deep gully that cuts through layers of Holocene and Eemian sediments and reaches into the Yarmouth Roads Formation. This part of the Yarmouth Roads Formation is a complex of fluvial sediments of late Early-Pleistocene, most probably Bavelian, age. The age of the Bavelian is considered to be some 1.000.000 - 750.000 years (1 - 0.75 Ma). As the fossils originate from the Yarmouth Roads Formation, the fauna is thus attributed a late Early Pleistocene age; we correlate it to localities such as Untermassfeld (Germany) and Saint-Prest (France), which both have an estimated age of c. 1 Ma. The faunal content of the site ‘Het Gat’ is provisionally as follows: (Proboscidea) Mammuthus meridionalis and/or Mammuthus trogontherii; (Artiodactyla) Hippopotamus antiquus, Alces latifrons, Megaloceros dawkinsi, Megaloceros savini, Eucladoceros ctenoides, Bison menneri; (Perissodactyla) Equus major, Stephanorhinus etruscus; (Carnivora) Homotherium cf. latidens, Ursus cf. etruscus. These finds necessitate us to discuss whether or not two different species of mammoth can have coexisted and can thus be present in one fossil faunal assemblage. There appears to have been a continuous evolutionary development leading from Early Pleistocene M. meridionalis to Late Pleistocene and Holocene M. primigenius. Most authors recognise an intermediate species M. trogontherii, of supposedly Middle Pleistocene age. The differences are in the dentition, while postcranially the taxa are difficult to distinguish. The molars we found in ‘Het Gat’ can either be interpreted as advanced M. meridionalis or as M. trogontherii. Until the taxonomy of Pleistocene Mammuthus species is clarified we doubt the presence of two species in one locality