Together with two colleagues from the Netherlands, Senckenberg scientist Ralf-Dietrich Kahlke examined the teeth of several macaques from the bottom of the North Sea. They constitute the first fossil evidence of Old World monkeys from the guenon family (Cercopithecidae) in the North Sea region. The primate teeth were unearthed during the artificial accretion of sand for the "Maasvlakte 2" harbor extension near Rotterdam in the Netherlands. The study was recently published in the scientific journal Revue de Paléobiologie.