Paleoenvironmental context and significance of a partial elasmosaurid skeleton from the Albian of Haute-Provence, France

Abstract

The Early-Late Cretaceous transition (late Albian-early Cenomanian; ~100 Ma) witnessed marked environmental changes and a deep reorganization of the marine fauna. The impact of these environmental and biotic changes on Tethyan marine vertebrates is poorly understood, due to a fragmentary fossil record. Here we report upper Albian marine vertebrate remains, including a partially articulated plesiosaurian skeleton, from a fossiliferous glauconite-rich bed in the Alpes de Haute-Provence, France. The fossiliferous horizon produced a diversified invertebrate fauna including ammonoids and belemnoids. The ammonite fauna is abundant and diversified, indicating the Mortoniceras fallax ammonite Zone. The calcareous nannofossil biomarkers date the bed to the NC10a Zone. The fossiliferous bed consists of glauconitic marls enriched in planktic foraminifera and occurs amongst a monotonous succession of alternating marlstones and limestone beds. The vertebrate fauna consists of chondrichthyans and marine reptiles. Chondrichthyans are represented by five Lamniformes species (dominated by Sphenodus) and comprise predator taxa probably living in open marine temperate waters. The site yielded a large, partial post-cranial plesiosaurian skeleton with articulated elements belonging to an elasmosaurid and representing one of the most complete Albian plesiosaurian specimens known from Europe. The abundance and preservation of the collected fossil remains are best explained by their concentration during a basin-scale episode of very low sedimentation corresponding to a major episode of marine transgression, associated with a lower oxygenation of bottom waters. These findings indicate that the newly discovered fossiliferous bed holds promising clues about the evolutionary history of major groups of marine vertebrates and ammonites near the Early-Late Cretaceous transition.

Sedimentary record of the “Austrian” tectonic pulse around the Aptian–Albian boundary in SE France, and abroad

“…G1 to G6, sandstone turbidite bed bundles. The "faisceau michoïde" was dated by Gale et al [2011] and also by a glauconite bed bearing ammonites of the Fallax zone [lowermost Vraconnian, Kilian Group (Reboulet S. et al), 2018] at its base [Vincent et al, 2020]. Correspondences with some peripheral platformal carbonates are indicated.…”

The Albian-Cenomanian transition in a shelf-basin transect: Biostratigraphy, sedimentology and paleontology of Jebel Mghila, Central Tunisia

“…During Albian time, elasmosaurids remain scarce but were widely expanded, having being reported from Canada by Wapuskanectes betsynichollsae Druckenmiller and Russell, 2006 and an indetermined specimen (Druckenmiller and Russell, 2006), Venezuela by Alzadasaurus tropicus Colbert, 1949(Colbert, 1949, Australia by Eromangasaurus australis (Sachs, 2005) and an indeterminated specimen (Sachs, 2005;Kear, 2006Kear, , 2007, and Europe by several indetermined or partial specimens (e.g., Persson, 1963;Bardet et al, 2016;Vincent et al, 2020).…”