Pleurotomaria DeFrance, 1826 (Gastropoda, Mollusca) from the Lower Bajocian (Middle Jurassic) sediments of Luxembourg, with considerations on its systematics, evolution and palaeobiogeographical history

Abstract

Pleurotomaria species from lower Bajocian (Middle Jurassic) sediments of south-western Luxembourg housed in the National Natural History Museum of Luxembourg are described. Seven species are recognized, one of which is new, Pleurotomaria faberi sp. nov. A more detailed definition of the diagnostic characters of the genus is proposed and the morphological continuity between Talantodiscus and Pleurotomaria is demonstrated, suggesting that the former cannot be considered as a distinct taxon. The palaeoecology, evolution and palaeobiogeographical history of Pleurotomaria are outlined. Pleurotomaria presumably first appeared in late Middle Triassic of New Zealand where it underwent a relative diversification up to the Hettangian (Early Jurassic). From early Hettangian, most of its evolutionary history took place in Europe and western Tethys. In the European epicontinental seas, Pleurotomaria experienced two important radiations. The first occurred in the Early Jurassic, with a peak in the late Pliensbachian, and was marked by an expansion of the distribution to the central part of western Tethys. After a collapse in species diversity, probably related to the early Toarcian anoxic event, a second radiation occurred. This culminated in the early Bajocian and was mainly confined in a region encompassing southern England, Paris Basin and southern Germany. Low-spired species, formerly attributed to Talantodiscus, probably originated independently and iteratively during the history of Pleurotomaria. The facies and associated benthic faunas suggest that Pleurotomaria probably lived on shallow soft bottoms composed of mixed calcareous-siliciclastic sediments. The two main Early Jurassic and early Middle Jurassic radiations of the genus took place in these environments. Records of the genus in Jurassic carbonate platform deposits are very few and concern mainly post-Bajocian species.

Gastropods of the Lower Jurassic Hierlatz Limestone Formation, part 3. New pleurotomarioideans from the fauna of Hierlatz Alpe (Hallstatt, Austria)

“…Th e interpretation of Pleurotomaria in this paper follows the suggestions by Monari & Gatto (2013). Th e measurements below concern the remnants of the shells without reconstruction; the standard measurements are usually not accessible.…”

The Jurassic pleurotomarioidean gastropod Laevitomaria and its palaeobiogeographical history

“…In the western European epicontinental seas, the pleurotomarioideans were mainly represented by long-ranging genera with high species diversity, such as Pleurotomaria Defrance, 1826, Bathrotomaria Cox, 1956, Pyrgotrochus Fischer, 1885, and Trochotoma Eudes-Deslongchamps, 1843(e.g., Sieberer 1907Cox 1960b;Fischer and Weber 1997;Gründel 2003;Kollmann 2005;Monari et al 2011;Monari and Gatto 2013). In contrast, these genera were either absent or rare and short-lived in the central region of western Tethys.…”

“…According to Monari and Gatto (2013), Pleurotomaria occurred in the western European shelf since the beginning of the Jurassic. In the Late Sinemurian, Pleurotomaria appeared also in those areas of the central region of western Tethys which were drowned by the Neotethyan rifting, concomitantly with the first appearance, early radiation and pronounced geographical expansion of Laevitomaria in these areas.…”

“…Again, Pleurotomaria occurred from the Early Jurassic to the Early Cretaceous in the European shelf, where it was represented by at least fifty species. In contrast, only few Sinemurian-Pliensbachian species are known from the pelagic sequences of central western Tethys (Monari and Gatto 2013).…”

“…Most of the material was collected from the Lower Bajocian sediments of the Differdange area (south-western Luxembourg) (see details in Monari and Gatto 2013). A few specimens come from Piedmont (Longwy, Lorraine, north-eastern France), a village located 5 km west of Differdange, where the same Bajocian succession crops out.…”