CEPHALOPODS FROM LA VOULTE-SUR-RHÔNE: A GLIMPSE ON DIVERSITY OF JURASSIC VAMPYROPODA (Invited Presentation)

The reconstruction of modern coleoid evolution suffers from the low preservation of soft tissues bounded to Lagerstätten separated by important stratigraphic gaps. Following recent molecular studies, a period of particular interest for coleoid evolution is the Jurassic for its high diversification rate probably related to the escalation of predatorial behavior in cephalopods (Tanner et al. 2017).

In this context, the La-Voulte-sur-Rhône lagerstätte (Jurassic, Callovian) provides unique insights on the detailed anatomy of these coleoids thanks to the iron rich mineralisation of their soft tissues. Six coleoid species from this locality were described in a series of studies mostly done by Fischer and Riou (ex : 1982a,b ; 2002). The systematic position of La-Voulte coleoids based on the external morphology is still debated and can now be reappraised using CT and propagation based phase contrast synchrotron CT techniques (proposal ESRF, ES-36). Results are here presented for several species such as Vampyronassa rhodanica, Mastigophora aff. brevipennis and undescribed specimens still embedded in the matrix. The preservation of internal structures is heterogeneous among the specimens. Some specimens preserve fine internal tissues such as gills, crop, ink sac and suckers. Such detailed preservation provides key information for comparisons with Recent coleoids, systematics based on soft tissues, character evolution and potential predation strategies.