Records of Trogontherium cuvieri Fischer, 1809 (Castoridae) from the Pleistocene of the Netherlands and the North Sea.

This paper provides new records of the extinct beaver Trogontherium cuvieri Fischer, 1809 from the Pleistocene of the Netherlands and the North Sea and summarizes earlier reports. We recorded T. cuvieri from 4 new sites and found 19 more in the literature, totalling 23 Dutch sites. We identified over 1000 new specimens, mostly in citizen scientist collections and predominantly from Maasvlakte 2, the artificial extension to the port of Rotterdam constructed from dredged sediments. Statistical tests indicate that many of the specimens from Maasvlakte 2 are significantly larger and those samples have a larger (coefficient of) variation than those from the classical locality of Tegelen. This suggests the ex situ Maasvlakte 2 and by extension the North Sea record consists of a mix of different populations of T. cuvieri, which fits with the temporally mixed North Sea Pleistocene record in general. The North Sea appears to be one of the richest sources of Trogontherium fossils available worldwide, possibly including some of the largest individuals known to date.