Our data, along with the recent records of genus in tropics of Indian Ocean, show the differentiation of the eastern and western Tethyan heterostegines in Priabonian
times and do not support a previous hypothesis that the genus was confined to the high-latitudes during this time.
It is during the Priabonian when the biodiversity decreased significantly in both sides of the Atlantic Ocean.
The Eocene succession is topped by the Priabonian Gendulain Formation (Puigdefabregas, 1975), which is composed of different types of coastal deposits, allowing its subdivision into three distinct members: lower evaporites, middle marls, and upper sandstones (Liedena Sandstone Member) (Fig.
The studied section culminates with the intertidal deposits of the Liedena Sandstone (Gendulain Formation) containing benthic microforaminifera of the Priabonian and abundant trace fossils of invertebrates and aquatic birds (Payros et al.
Spondylus caldesensis, Spondylus bifrons and Spondylus nysti are present in several sites of Igualada, Manresa and Vic regions, in the Igualada Formation (late Bartonian, most likely Priabonian in age, Taberner et al.