Exceptionally preserved arthropodan microfossils from the Middle Ordovician Winneshiek Lagerstätte, Iowa, USA

This work was funded by the ANR (Agence National de la Recherche, France) as part of the ‘RALI – The Rise of Animal Life’ project (Grant number ANR-11-BS56-0025), and by the NSF of USA (grant numbers EAR 0921245 and EAR 0922054). Acid treatment and slide preparation were conducted by Laurence Debeauvais (CNRS/Universite Lille 1). Paul K. Strother (Boston College) found the first possible xiphosuran coxae in our material. Massimo Morpurgo (Museum of Nature South Tyrol) provided exuviae of Limulus polyphemus. We thank James C. Lamsdell (Yale University), Petra Tonarova (Tallinn University of Technology, Czech Geological Survey), Olle Hints (Tallinn University of Technology), Denis Audo (Universite de Rennes 1), Carolin Haug (LMU Munich), Joachim T. Haug (LMU Munich) and Alexander Blanke (Hull, UK) for discussing our findings, and two anonymous reviewers for their helpful comments. This work is a contribution to IGCP project 653 – ‘The onset of the Great Ordovician Biodiversification Event’ and to the CPER research project CLIMIBIO. The authors thank the French Ministere de l'Enseignement Superieur et de la Recherche, the Hauts-de-France Region and the European Funds for Regional Economic Development for their financial support to this project and the Department of Innovation, Research and University of the Autonomous Province of Bozen/Bolzano for covering the Open Access publication costs.