CHAPTER THREE Constraining the Deep Origin of Parasitic Flatworms and Host- Interactions with Fossil Evidence Kenneth De Baets*,1, Paula Dentzien-Diasx, Ieva Upeniece{, Olivier Verneaujj,#,**, Philip C.J. Donoghuexx *Fachgruppe Pal€aoUmwelt, GeoZentrum Nordbayern, Friedrich-Alexander-Universit€at Erlangen-Nurnberg,€ Erlangen, Germany x Nucleo de Oceanografia Geologica, Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, Brazil { Department of Geology, University of Latvia, Riga, Latvia jj Centre de Formation et de Recherche sur les Environnements Méditerranéens, University of Perpignan Via Domitia, Perpignan, France #CNRS, Centre de Formation et de Recherche sur les Environnements Méditerranéens, Perpignan, France **Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa xx School of Earth Sciences, University of Bristol, Life Science Building, Bristol, UK 1Corresponding author: E-mail:
[email protected] Contents 1. Introduction 94 2. Assessment of the Flatworm Fossil Record 96 2.1 Devonian fossil hook circlets 97 2.2 Silurian blister pearls and calcareous concretions in bivalve shells 101 2.3 Permo-Carboniferous egg remains in shark coprolites 103 2.4 Cretaceous egg remains in terrestrial archosaur coprolites 105 2.5 Eocene shell pits in intermediate bivalve hosts 106 2.6 Eggs remains in a Pleistocene mammal coprolite 107 2.7 Holocene evidence for parasitic flatworms from ancient remains 107 2.8 Free-living flatworms 108 3. Interpolating or Extrapolating Extant ParasiteeHost Relationships and the 110 Assumption of ParasiteeHost Coevolution 4. Molecular Clock Studies 113 5. Conclusions and Future Prospects 119 Acknowledgements 121 References 122 Abstract Novel fossil discoveries have contributed to our understanding of the evolutionary appearance of parasitism in flatworms.