Gastropods underwent a major taxonomic turnover during the end-Triassic marine mass extinction event

Abstract

Based on an exhaustive database of gastropod genera and subgenera during the Triassic–Jurassic transition, origination and extinction percentages and resulting diversity changes are calculated, with a particular focus on the end-Triassic mass extinction event. We show that gastropods suffered a loss of 56% of genera and subgenera during this event, which was higher than the average of marine life (46.8%). Among molluscs, gastropods were more strongly affected than bivalves (43.4%) but less than ammonoids, which were nearly annihilated. However, there were also pronounced differences among gastropod subclasses. The most strongly affected subclass was the Neritimorphia, which lost 72.7% of their Rhaetian genera; on the other extreme, the Heterobranchia remained nearly unaffected (11% loss). We analysed this extinction pattern with respect to larval development, palaeobiogeography, shell size, and anatomy and found that putative feeding of the pelagic larval stage, adaptation to tropical-temperate water temperatures, and flexibility of the mantle attachment were among the factors that might explain extinction resilience of heterobranchs during the end-Triassic crisis. Among molluscs, extinction magnitude roughly correlates with locomotion activity and thus metabolic rates. We suggest three potential kill mechanisms that could account for these observations: global warming, ocean acidification, and extinction of marine plankton. The end-Triassic extinction of gastropods therefore fits to proposed extinction scenarios for this event, which invoke the magmatic activity of the Central Atlantic Magmatic Province as the ultimate cause of death. With respect to gastropods, the effect of the end-Triassic mass extinction was comparable to that of the end-Permian mass extinction. Notably, Heterobranchia was relatively little affected by both events; the extinction resilience of this subclass during times of global environmental changes was therefore possibly a key aspect of their subsequent evolutionary success.

The distribution and evolutionary dynamics of dopaminergic neurons in molluscs

“…With over 30,000 species, euthyneuran gastropods represent one of the most diverse lineages in Mollusca, and play significant ecological roles in aquatic and terrestrial environments (Ferrari and Hautmann, 2022). The presence of large, identified neurons in representatives of Euthyneura justified the early focus on dopamine signaling with TH-ir or glyoxylate-induced histofluorescence mapping.…”

First report of Euthyneura (Heterobranchia: Gastropoda) in the Early Jurassic of Southern Patagonia, Argentina

“…The Late Triassic Cylindrobullina species from Peru showed the smallest size for the genus at that time, whereas the Pliensbachian Cylindrobullina of southern Patagonia showed the largest size. The Pliensbachian increased size of austral Cylindrobullina species was considered by Ferrari and Hautmann (2022) to be related to a Pliensbachian cooling event (Korte et al, 2015); thus, largest specimens of Cylindrobullina (up to 30 mm) stem from the Pliensbachian of high paleolatitudes (south Patagonia) with inferred cold palaeotemperatures. Ferrari and Hautmann (2022) also suggested that the post extinction size increase of Cylindrobullina might have resulted from ecological (Gründel, 2010;Gründel and Nützel, 2012).…”

“…This conclusion is supported by the phylogenetic analysis of Dinapoli and Klussmann-Kolb (2010), who indicated an occurrence of the Euthyneura stem line between the Middle Carboniferous and the Early Triassic and a first diversification of the clade between the Permian and the Triassic. The Early Mesozoic euthyneuran bubble snails in the extinct families Cylindrobullinidae and Tubiferidae are very similar in general shell morphology and ornamentation pattern to the extant Acteonidae and Ringiculoidea (see Kano et al, 2016;Ferrari and Hautmann, 2022). Thus, the common ancestor of Euthyneura might have had a thin, oval shell-shaped with a large body whorl, an elongated aperture and smooth surface with or without fine spiral cords, as is shown in early Mesozoic opisthobranchs (e.g., Cylindrobullina, Cossmannina, Conactaeon, Euconactaeon, Sinuarbullina).…”

“…Thus, the common ancestor of Euthyneura might have had a thin, oval shell-shaped with a large body whorl, an elongated aperture and smooth surface with or without fine spiral cords, as is shown in early Mesozoic opisthobranchs (e.g., Cylindrobullina, Cossmannina, Conactaeon, Euconactaeon, Sinuarbullina). Ecologically, these characters typically occur in species with an infaunal or temporarily borrowing mode of life (Ferrari and Hautmann, 2022).…”