Late Toarcian marine gastropods from the Cleveland Basin, UK: systematics, palaeobiogeography and contribution to biotic recovery from the early Toarcian extinction event

MARIEL FERRARI; LITTLE CRISPIN; ATKINSON JED

Erlangen

Workshop; 3rd International Workshop and Fieldtrip of IGCP 655 Toarcian Oceanic Anoxic Event: Impact on marine organisms and ecosystems; 2019

As part of a study to evaluatethe recovery from the early Toarcian extinction event in the Cleveland Basin(see the Atkinson, Little and Dunhill abstract), 477 new gastropod specimenswere collected from mid-late Toarcian rocks of the Ravenscar section, NorthYorkshire, UK. The gastropods were preserved in two modes: 1) specimenspreserved with recrystallized shells, mainly in the Whitby Mudstone Formation,but also some in the Blea Wyke Sandstone Formation; 2) specimens preserved asexternal moulds in mineralized patches of shells in the Yellow SandstoneMember. The fossil assemblage comprised fifteen species, of which three arenew: Katosira? bicarinata sp. nov., Turritelloideastepheni sp. nov. and Striactaenonina elegans sp. nov. Four species are described in open nomenclature,as Tricarilda? sp. Jurilda sp., Cylindrobullina sp. and Cossmanninasp. The other species have previously been described: Coelodiscus minutus (Schübler in Zieten), Procerithium quadrilineatum (Römer), Pseudokatosira undulata (Benz in von Zieten), Palaeorissoina aff. acuminata(Gründel), Pietteia unicarinata(Hudleston), Globularia cf. canina (Hudleston), Striactaeonina cf. richterorumSchulbert & Nützel, Striactaenoninaaff. tenuistriata (Hudleston) and Sulcoactaeon sedgvici (Phillips). Mostof these species are the earliest records of their respective genera and showpalaeobiogeographical connections with contemporary gastropod associations fromother regions of Europe and South America. The taxonomic composition of thelate Toarcian Cleveland Basin gastropod assemblage differs substantially fromthe faunas of the late Pliensbachian and early Toarcian Tenuicostatum Zone, showing the strong effect of the early Toarcianmass extinction event on the marine gastropod communities in the basin. Only afew gastropod species are shared between the late Toarcian faunas and the muchmore diverse Aalenian gastropod faunas in the Cleveland Basin, suggesting therewas a facies control on gastropod occurrences at that time. This is also apotential explanation for the taxonomic differences between the late Toarciangastropod faunas in the Cleveland Basin and those in France, and Northern and SouthernGermany.