The first cetacean from the early Oligocene of the SW German Mainz Basin: a probable cheek tooth of a mysticete (Mammalia: Cetacea)

Despite two centuries of fossils collecting, no cetacean remains from the Oligocene marine deposits of the Mainz Basin (western Germany) have ever been reported. Here, we describe a possible mysticete tooth from the sand pit of Eckelsheim, which exposes high energy deposits belonging to the Rupelian Alzey Formation. The latter has yielded a rich assemblage of vertebrates and invertebrates, but so far, only one marine mammal in the form of the sirenian Kaupitherium . The whale tooth in some ways resembles the m2 of Llanocetus from the latest Eocene of Seymour Island, Antarctica. If the find from the Mainz Basin is not a regionally evolved form, Llanocetus , which is known from the South Atlantic, could have migrated through the Atlantic realm during the early Oligocene. It cannot be excluded that the tooth represents a more widely occurring lineage, neither endemic nor necessarily related to llanocetids, that—given the generally poor Rupelian record—has not been well documented yet.