Open Access

Chien-Hsiang Lin, Etienne Steurbaut, Dirk Nolf

• A collection of 1149 otoliths of the Ypresian and Ypresian–Lutetian transition (early Eocene) from 18 sites across five states in the eastern and southern regions of the USA was analyzed. In total, 33 otolith-based taxa are documented, of which 27 are identified at the species level. Nine of these are introduced as new species: “Conger” biaculeatus sp. nov., Bauzaia gibbosa sp. nov., Ampheristus brevicaudatus sp. nov., Symmetrosulcus virginicus sp. nov., Neobythites longesulcatus sp. nov., “Neobythites” pamunkeyensis sp. nov., “Neobythites” stringeri sp. nov., Waitakia dorsogibbosa sp. nov., and “Haemulon” ypresiensis sp. nov. The assemblages are distinct when compared to their younger Eocene counterparts in America. This distinction is primarily characterized by the high proportion of the newly introduced species or exclusive Ypresian species. Additionally, we highlight the presence of 10 amphi-Atlantic species originally described in European deposits. Significantly, the composition of the otolith collection supports the interpretation of a shallow-water environment for the sampled sites during the Ypresian. This ecological setting appears to persist into the subsequent middle and late Eocene within the same geographic region.