Vetigastropoda and Neritimorpha from the Lower Bajocian of Luxembourg and palaeobiogeography of Aalenian–Bajocian (Middle Jurassic) gastropods of western Europe

Abstract

Vetigastropod and neritimorph species from Lower Bajocian (Middle Jurassic) sediments of south-western Luxembourg are described. Eighteen species are recognized. Two new genera – Szabotomaria gen. nov. and Fabercapulus gen. nov. – and four new species – Szabotomaria ziqquratiformis sp. nov., Colpomphalus thuyi sp. nov., Colpomphalus tigratus sp. nov. and Fabercapulus semisculptus sp. nov. – are erected. These species, together with other species recently described from the same strata, are part of a diverse assemblage consisting of 32 species belonging to 14 genera in six families and five superfamilies, representing the richest vetigastropod-neritimorph fauna currently known from Bajocian and sub-coeval deposits of western Europe. An analysis of the palaeoecological and palaeobiogeographical relationships of this fauna and those from other areas of the western European shelf was performed using cluster analysis and by comparison of the respective taxonomic structures. The former detected a major cluster composed of two distinct branches: the faunas of the northern Paris-Wessex Basin, including Luxembourg, and those of the southern Germany basin. These faunas have similar taxonomic structures and occur mainly in facies represented by condensed iron ooid-rich marls and limestones deposited in lower offshore to upper offshore-shoreface settings. The close relationship between the Luxembourg and other faunas of the Paris-Wessex Basin reflects free faunal exchange and facies similarities. Slight differences in the sedimentary context could explain the separation of the southern German from the Anglo-Paris branch, whereas similarities between Swabian and Franconian faunas most probably reflect the geographical continuity of these areas. The Early Bajocian fauna of the East Midlands Shelf comes from sediments deposited in a shallow-water, oolitic barrier complex and is different from\ud other western European faunas in both species composition and taxonomic structure

Early Jurassic (Sinemurian) gastropods from the Lusitanian Basin (west of Portugal)

“…For this reason, they substituted the family name Ataphridae with Collonidae. However, Monari et al (2018) maintained that this view is not justified. According to these authors, although the holotype is imperfectly preserved, it shows all the characters indicated in the original diagnosis and the uncertainty about its origin does not affect the availability of the taxon.…”

Gastropods from the Jurassic neptunian sills of Rocca Busambra (north‐western Sicily, Italy): Patellogastropoda, Pleurotomarioidea, Scissurelloidea, Fissurelloidea and Eucycloidea

“…He also tentatively classified most of the specimens of the other groups (Wendt 1971). The Trochoidea, Turbinoidea and supposed Rissooidea were treated in subsequent papers concerning the systematics of the gastropods at higher taxonomic rank (Conti et al 1993;Szabó et al 1993;Monari et al 1996). Conti et al (2004) reported a synthesis of the knowledge acquired so far in the study of these faunas.…”

“…The illustration of the type species (Das 2002, p. 104, text-figs 3, 4A-B) shows a very poorly preserved material which prevents more detailed comparisons. Pleurotomaria Defrance, 1826 has a more gradate shell and flatter base, the shoulder of the adult shell is provided with a row of nodes and the selenizone runs on the outer face (Monari & Gatto 2013).…”

“…The genera ascribed here to the family Pleurotomariidae Swainson, 1840 share with Pleurotomaria Defrance, 1826 the earliest teleoconch whorls that are evenly convex, ornamented by a sharp and regular network of spiral threads and collabral riblets, and bearing a concave to flat selenizone at or slightly below mid‐whorl (Monari & Gatto 2013). A very similar early teleoconch is present in other pleurotomariid genera, like Bathrotomaria Cox, 1956, Leptomaria E. Eudes‐Deslongchamps, 1864, Obornella Cox, 1959 and Szabotomaria Monari et al ., 2017 (Monari & Gatto 2014; Monari et al . 2018).…”

“…In these areas the deposition of pelagic carbonate mud and shale started and persisted throughout the Jurassic period and, especially in topographically elevated areas that became scene of condensed pelagic sedimentation, gastropod communities developed which were profoundly different from those of the epicontinental seas and of the Tethyan shallow water carbonate platforms. Most of these faunas are known from Sinemurian to Pliensbachian and from Bajocian sediments of several palaeogeographical units, such as the Transdanubian Range (Hungary) (Szabó 1979(Szabó , 1980(Szabó , 1981(Szabó , 1982(Szabó , 1983(Szabó , 1995(Szabó , 1996(Szabó , 2008 limestones of the Lattimusa Formation disconformably overlie the Buccheri Formation and represent the youngest deposits cropping out at Piano Pilato.…”