Gastropods from upper Pliensbachian–Toarcian (Lower Jurassic) sediments of Causses Basin, southern France and their recovery after the early Toarcian anoxic event

A new gastropod species, Bathrotomaria kronzwilmesorum, was identified from Lower Jurassic sediments of the Causses Basin, southern France, revealing insights into post-anoxic event recovery. The study found that gastropod diversity peaked during the Bifrons and Aalensis zones, indicating brief periods of stable oxygen levels and favorable seabed conditions. However, diversity plummeted in the Variabilis–Pseudoradiosa zones, suggesting severe environmental instability that only allowed highly adaptive species to survive. The slow and discontinuous faunal recovery was attributed to the Causses Basin's geographic isolation, which restricted faunal exchange with western European seas, preventing faster colonization by more diverse Tethyan taxa. This research highlights the impact of physiographic factors on biodiversity resilience during ancient environmental crises.

GATTO, R., MONARI, S., NEIGE, P., PINARD, J.-D., & WEIS, R. (2015). Gastropods from upper Pliensbachian–Toarcian (Lower Jurassic) sediments of Causses Basin, southern France and their recovery after the early Toarcian anoxic event. Geological Magazine, 152(5), 871–901. https://doi.org/10.1017/s0016756814000788