Abstract
Bradoriid arthropods (class Bradoriida) are described for the first time from the lower–middle Cambrian boundary interval (regional Agdzian Stage) of the Franconian Forest in eastern Bavaria, Germany. The specimens originate from the Tannenknock and Triebenreuth formations, which are part of a shallow marine succession deposited at the margin of West Gondwana. Five different forms have been distinguished, Indiana aff. dermatoides (Walcott), Indiana sp., Indota? sp., Pseudobeyrichona monile sp. nov., and an undetermined svealutid, all of which belong to families that have previously been reported from and are typical of West Gondwana. However, at the generic level, all taxa are new for the region. Indiana is typical of shallow marine environments. So far it has been reported from Laurentia, Avalonia, and Baltica, and is considered to characterize the paleogeographic vicinity of Cambrian continents. Pseudobeyrichona has previously only been recorded from South China, and its new occurrence corroborates previous documentation of taxa from South China in northern West Gondwana. The presence of Indiana as a typical “western” taxon and Pseudobeyrichona among other typical “eastern taxa” confirms the unique biogeographical position of West Gondwana. The poorly known Indiana anderssoni (Wiman) and Indiana minima Wiman from the late early Cambrian of Scandinavia have been restudied in order to re-evaluate the two species and to refine the definition of Indiana. Indiana anderssoni represents a distinct species of Indiana, whereas I. minima is a pseudo-fossil.
Highlights
The Cambrian of the Franconian Forest area (German: Frankenwald) in north-eastern Bavaria has long been known from only a few moderately diverse middle Cambrian trilobite assemblages (e.g., WurmHandling Editor: Peter Frenzel.1925a, 1928; Sdzuy 1964, 1966, 2000)
This study presents the first discovered representatives of the Bradoriida, a group of small bivalved basal euarthropods (e.g., Hou et al 2010), from Cambrian strata of the Franconian Forest area
These characters include the size of the valves, the lack of any lobation, and the angles enclosed by the antero- and posterodorsal margins with the hinge line, which are similar to angles observed in species of Indiana (e.g., Siveter and Williams 1997)
Summary
The Cambrian of the Franconian Forest area (German: Frankenwald) in north-eastern Bavaria (southern Germany; Fig. 1) has long been known from only a few moderately diverse middle Cambrian trilobite assemblages Specimens described as Indianites caenensis Cobbold, 1935 were the first bradoriids reported from France, and represent the oldest species currently known from West Gondwana This poorly known taxon, which might be a simple svealutid (see the “Discussion” of Indiana below), is from the Saint-Jean-de-la-Rivière Formation near Carteret, Normandy (e.g., Doré 1994), where it cooccurs with Bigotina bivallata Cobbold, 1935, indicating an early “Ovetian” (= early Issendalenian) age (Bigotina Biozone; see e.g., Gozalo et al 2003, Zhang et al 2017, Geyer, in press). The recently reported svealutid and kunmingellid specimens from the Czech Republic (Fatka et al 2014) increase the middle Cambrian diversity in West Gondwana, a diversity that is further corroborated by the five middle Cambrian taxa from the Franconian Forest described below They belong to the families Bradoriidae, Hipponicharionidae Sylvester Bradley, 1961, and Svealutidae. Bradoria Matthew, 1899 (= Bradorona Matthew, 1902; ?= Ifersiktia Hinz-Schallreuter, 1993); Walcottella Ulrich and Bassler, 1931a; Indiana Matthew, 1902 (= Indianites Ulrich and Bassler, 1931b); Indota Öpik, 1968 (?= Tropidiana Öpik, 1968) (see Siveter and Williams 1997 and Streng et al 2008)
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