[2] In 1898, Swiss marine biologist Théophile Rudolphe Studer said O. meyeri was a subjective synonym of Delphinus acutidens, and there is room for debate on the question of the former's validity.

[4] In 1905, Austrian paleobiologist Othenio Abel considered D. acutidens to be synonymous with the sperm whale Physeterula dubusi.

[8] Central Europe, at this time, probably represented an upwelling area along a continental shelf, which attracted a variety of sea life, including swarming fish.

[9] Land was probably dominated by nearshore swamps which emptied into the sea, and the area featured ancient beavers, hedgehogs, several river turtle species, and various other semi-aquatic creatures.

[10] The sea progressively moved southwards, and the connection to the ocean closed about 17 million years ago (mya), turning the area into a system of brackish and freshwater lakes.