Acknowledgments

MRS-V and OA thank R. Sánchez (Urumaco) and A. Pulgar (Taima Taima) for permission to work in the field in Venezuela. We thank W. Etter (Naturhistorisches Museum Basel) for access to echinoid material and A. B. Smith (London) and R. Portell (Gainesville) for commenting on early versions of the manuscript and for the discussion of ideas and access to important literature. This work was financially supported by the Paläontologisches Institut und Museum of Zürich University.