Geological location of the Castejón de Sobrarbe-41 fossil site. (a) Palaeogeography of NW Europe during the early Paleogene indicating the location of the studied area (blue areas: sea; green areas: land). Latitudes indicated are palaeolatitudes. Modified after Astibia, H. et al.20 New fossils of Sirenia from the middle Eocene of Navarre (Western Pyrenees): the oldest West European sea cow record, Geological Magazine, 147, 665–673 (2010), reproduced with permission. (b) A simplified geological map of the studied area with the location of the middle Lutetian sirenian fossil site of Castejón de Sobrarbe-41 (CS-41), Huesca (Spain). Modified with permission from Mochales et al.37. Anisotropic magnetic susceptibility record of the kinematics of the Boltaña Anticline (Southern Pyrenees), Geological Journal, John Wiley and Sons. Software used: inkscape 0.91 https://inkscape.org/en/release/0.91/.