Platyceratid gastropods - stem group of patellogastropods, neritimorphs or something else?

Abstract

A systematic study of Silurian and Devonian platyceratid gastropods provides new data on their early shell ontogeny. Typical cyrtoneritimorph protoconchs were found in <i>Praenatica cheloti </i>(Oehlert & Oehlert, 1887) from the Lower Devonian strata of Brittany (W France). The same protoconch type, as in <i>Praenatica</i> Barrande in Perner, 1903, was earlier documented in <i>Orthonychia </i>Hall, 1843. Both of the latter taxa have often been considered to be subgenera of <i>Platyceras</i> Conrad, 1840. However, Silurian and Devonian species of <i>Platyceras</i> from the Barrandian area develop quite different protoconchs (orthostrophic and tightly coiled), similar to those found earlier in different species of the family Naticopsidae Waagen, 1880. Current data suggests that Paleozoic platyceratids represent a diphyletic group. The nature of their protoconchs (development of a true larval shell) testifies against the hypothesis that the Paleozoic platyceratids are the stem group for the Patellogastropoda. However, the derivation of modern neritimorphs from Paleozoic “platyceratids” with tightly coiled protoconchs or from the naticopsids seems to be probable. The strongly convolute neritimorph protoconch (apomorphy of neritimorph crown-group) probably originated after the Permian/Triassic mass extinction event, but before the Late Triassic

Lingulate brachiopods from the Chýnice Limestone (upper Emsian, Barrandian; Czech Republic)

“…Chlupáč (1983) referred the fauna of the Chýnice Limestone to the Orbitoproetus-Scabriscutellum trilobite assemblage. Its trilobites and brachiopods have been reviewed by Havlíček & Vaněk (1996), and other invertebrate groups have more recently been studied (Frýda 2001;Frýda et al 2008Frýda et al , 2009. Biostratigraphically the Chýnice Limestone may be characterized by goniatites (Mimagoniatites), conodonts (Polygnathus groenbergi; Klapper 1977) and dacryoconarid tentaculites.…”

High-resolution tentaculite biostratigraphy and facies development across the Early Devonian Daleje Event in the Barrandian (Bohemia): implications for global Emsian stratigraphy

“…A list of fossils from this locality (often called Bubovice) was published by Chlupáč (1957Chlupáč ( , 1959, Chlupáč et al (1979Chlupáč et al ( , 1998, and Havlíček & Vaněk (1996). Newly described taxa from the Čeřinka hillside section include inarticulate brachiopods, trilobites, and gastropods (Vaněk 1998;Frýda 2001;Frýda et al 2008bFrýda et al , 2009Budil et al 2009;). During the years 2006 to 2010, this section was intensively studied by Lenka Ferrová.…”

“…The upper part of the Chýnice Limestone, with an even higher diversity, is currently studied by the senior author. Publications evaluating the entire fauna are in preparation; three short papers based on these newly collected materials have already been published (Frýda et al 2008b(Frýda et al , 2009). …”

“…Subsequently, the new food source structures caused changes in ontogenetic strategies and/or radiation of some groups of invertebrates and vertebrates (e.g., Signor & Brett 1984;Bambach 1999;Nützel & Frýda 2003; Klug predation pressure on the new Devonian planktonic groups (e.g., Berkyová et al 2007) as well as the new food sources influenced evolution in the majority of marine invertebrates . For example, three of the five living gastropod orders, which form the most diversified of all living marine invertebrate groups, probably originated during the Early Devonian (Bandel 1997;Nützel 1998;Frýda 2012;Frýda et al 2008aFrýda et al , 2009Frýda & Blodgett 2004;Nützel et al 2007a). Increasing predation pressure and the existence of new food sources in the ocean surface waters is also linked with the extensive changes in gastropod protoconch morphology and adaption of some new groups on larval planktotrophy (Nützel & Frýda 2003;Nützel et al 2006Nützel et al , 2007aFrýda et al 2009;Seuss et al 2012).…”

Armoured test of Early Devonian Mesoconularia (Conulariida) from the Prague Basin (Czech Republic): probable adaptation to increased predation pressure

“…The fauna collected there was summarized by Chlupáč (1957), Chlupáč et al (1979, Kovanda et al (1984), and Havlíček & Vaněk (1996). During the last two decades several new studies focusing on brachiopods ) and gastropods (Frýda 2001;Frýda et al 2008Frýda et al , 2009 were published. Ferrová (2010) and Ferrová et al (2012), based on a bed by bed study of two sections at the classical Čeřinka locality and in the nearby Čerinka Quarry, described in detail the environmental changes across the Daleje Event and proposed a new mid-Emsian tentaculite biostratigraphy as well as a new boundary for the Dalejan (= "Upper Emsian").…”