Slit-band gastropods (Pleurotomariida) from the Upper Triassic St. Cassian Formation and their diversity dynamics in the Triassic

Abstract

The St. Cassian Formation, Italy, has yielded the most diverse marine invertebrate fauna known from the Triassic. A quarter of all described Triassic gastropod species has been reported from this formation. Most of the gastropod species from the St. Cassian Formation were erected in the 19th century and many of them are known only from their original figures and descriptions. The failure to study type specimens resulted in many erroneous identifications by subsequent authors. Here, we revise the slit band gastropods (Pleurotomariida) from the St. Cassian Formation—one of the major groups present in this formation. A total of 77 nominate Pleurotomariida species belonging to 29 genera and 11 families are present in the St. Cassian Formation which comprises approximately 14 % of the total nominate gastropod species of that formation. In addition, we revise several taxa that had been wrongly assigned to Pleurotomariida. As other gastropod clades, Pleurotomariida experienced a major extinction at the end-Permian mass extinction event. As in the Late Palaeozoic, their relative abundance in gastropod faunas continued to be 30 % in some Anisian faunas but decreased to 5–10 % afterwards. Their diversification at generic level became interrupted by an extinction event within the Carnian, probably by the Carnian Pluvial Event. As a result of their sluggish recovery compared to the other gastropod groups, their species diversity decreased from 26 % during the Permian to 18 % during the Triassic.
 Type specimens of the following genera are studied: Proteomphalus, Rhaphistomella, Temnotropis, Kittlidiscus, Stuorella, Schizogonium, Wortheniella, Bandelium, Lancedellia, Rinaldoella, Pseudowortheniella, Paleunema, Ampezzalina, Bandelastraea, Cheilotomona, Pseudoscalites, Delphinulopsis, and Cochlearia.
 Nine new pleurotomariidan genera are erected: Amplitomaria, Pseudoananias, Lineacingulum, Pressulasphaera, Cancellotomaria, Acutitomaria, Lineaetomaria, Nodocingulum, and Striacingulum.
 Eight new species are described: Schizogonium undae, Acutitomaria kustatscherae, Wortheniella klipsteini, Wortheniella paolofedelei, Rinaldoella tornata, Nodocingulum ernstkittli, Nodocingulum? turris, and Laubella subsulcata.
 Eoworthenia frydai is a new replacement name for Worthenia rarissima Barrande.

Drilling predation on Early Jurassic bivalves and behavioral patterns of the presumed gastropod predator—evidence from Pliensbachian soft-bottom deposits of northern Germany

“…and W.W., personal observation). Even the species endemic to southern Germany are small compared with the widely distributed co-occurring species from the same genus (Karapunar et al 2021). Smaller size can be an adaptation to finer sediment grain size, less oxygen availability (Fürsich et al 2020), and higher temperature (Piazza et al 2019, 2020).…”

Taxonomy and diversity of slit‐band gastropods (Order Pleurotomariida) and some slit bearing Caenogastropoda from the Pennsylvanian of the USA

“…2 fig. 18) and in developing the selenizone very late during ontogeny (Karapunar & Nützel 2021). Its type species, Stuorella subconcava (Münster, 1841), develops nodes on the selenizone but not all members of this genus do that.…”

“…The Triassic species Pleurotomaria subcancellata d´Orbigny, 1850 was assigned to Dictyotomaria by Bandel (1991, 2009). This species is not considered to be Dictyotomaria any longer and represents the type species of Cancellotomaria (Karapunar & Nützel 2021).…”

“…Erwin (1993) noted that Pleurotomariida declined drastically during the extinction but rebounded quickly thereafter. Karapunar & Nützel (2021) showed that the recovery of the group was slower compared to other gastropod groups in the Triassic. As a result, their species diversity decreased from 26% during the Permian to 18% during the Triassic.…”

“…The marginal diversity of modern Pleurotomariida is in sharp contrast to the high fossil diversity particularly during the middle and late Palaeozoic, as reflected by a high number of genera and species during the Devonian and Permian periods (Hickman 1984; Harasewych 2002). Their diversity remained relatively high during the Triassic (Karapunar & Nützel 2021). The diversity of Pleurotomariida has diminished markedly several times: during the end‐Devonian, end‐Permian, end‐Triassic and end‐Cretaceous mass extinctions.…”