Euclastidae n. fam. (Chelonioidea) et première mention d’Euclastes Cope, 1867 dans le Paléocène du bassin de Paris (France)

Two new Chelonioidea Oppel, 1811 marine turtle dentaries from two Paleocene sites in the Paris Basin (Oise) represent the oldest European occurrences of the genus Euclastes Cope, 1867, along with Eu. wielandi (Hay, 1908) from Laversines (Danian), and Eu. montenati n. sp. from Therdonne (Thanetian). The family Euclastidae n. fam. is erected and includes the genera Euclastes Cope, 1867 (type species Eu. platyops Cope, 1867), Mexichelys Parham & Pyenson, 2010 (type species Mexichelys coahuilaensis (Brinkman, Aquillon-Martinez, De Leon da Vila, Jamniczky, Eberth & Colbert, 2009)) and Pacifichelys Parham & Pyenson, 2010 (type species Pacifichelys hutchisoni (Lynch & Parham, 2003)), Erquelinnesia Dollo, 1887 (type species Erquelinnesia gosseleti (Dollo, 1886)) and Glossochelys Seeley, 1871 (type species Glossochelys planimentum (Owen, 1842)). It corresponds to the “Euclastes group” of Jalil et al. (2009) and the “Euclastes clade” of Parham (2005) and includes taxa previously placed in the Osteopyginae Zangerl, 1953 (type genus Osteopygis Cope, 1868), which is a chimaeric subfamily. Indeed, Zangerl (1953) included in the type species Osteopygis emarginatus Cope, 1869 (whose holotype is a non-chelonioid postcranial) species from the same levels (Paleocene, New Jersey) but with chelonioid skulls. Within the new family, two informal groups are recognized, those of Euclastes and Erquelinnesia, a genus also present in the Paleocene of the Paris Basin. Among the Chelonioidea, whose various secondary palate types are examined, the Euclastidae n. fam. is differentiated from the Toxocheyidae Baur, 1895 sensu Zangerl (1953) and the Cheloniidae Oppel, 1811. The Euclastidae sites are studied: for the first time, lithological correlations are highlighted between the Danian limestone beds from Laversines and the Thanetian Bracheux sands from Bracheux (Butte de la Justice), Therdonne (Oise) and Rollot (Somme). The successive transgressions of the Danian and Thanetian seas in the Paris Basin are illustrated. Stratigraphic, lithological, paleogeographic and environmental contexts (associated faunas, crushing diet) are studied. The distinctly marine level at Bracheux and Rollot, with Erquelinnesia, is distinguished from that with Euclastes from Laversines and Therdonne, the latter more littoral with continental inputs, including a new pleurodire ?cf. Bothremydidae. The worldwide distribution of Euclastidae n. fam. is examined.