Middle Cambrian Bradoriida (Arthropoda) from the Franconian Forest, Germany, with a review of the bradoriids described from West Gondwana and a revision of material from Baltica

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.

Bradoriids (Arthropoda) and the Cambrian Diversification

“…Phosphatocopids, a Cambrian group like bradoriids also once referred to the Ostracoda, are distinguished from bradoriids by "the presence of a doublure on the free margin" [6]. Exceptions to this may occur, however, as the Australian bradoriid Zepaera jagoi shows a clear doublure/duplicature at the edge of the shield [19]. The majority of bradoriids have postplete or amplete shield shape, although a few are preplete ( Figure 3); preplete shape is more characteristic for phospatocopids [20,21].…”

“…Bradoriids may have had as many as nine molt stages, and their assemblages tend to be monotypic [24]. Bradoriid species are also known for their high degree of morphological variability [19].…”

“…The same is true, perhaps even more so, of the bradoriid Pseudobeyrichona monile with its wing-shaped shields [19]. Matthoria troyensis also has a postplete shield shape well suited to shield-rowing locomotion, with a bluntly pointed extension at the ventral most part of the marginal rim [20].…”

“…The type species of the genus is middle Cambrian (Cambrian Series 3, Wuliuan; Albrunnicola oelandicus [43]), and occurs in Öland, Sweden, in the Borgholm Formation [31]. Interestingly, the subspecies Albrunnicola oelandicus maroccanus Hinz-Schallreuter, 1993 has been reported from the central Anti-Atlas of Morocco [19]. Albrunnicola has an interesting paleobiogeographic distribution, occurring in Laurentia, Australia, and Antarctica [31].…”

“…Bullaluta is a western Newfoundland bradoriid of Furongian (Late Cambrian) age [19]. It has a non-lobate shield [19], with a pustulose appearance where the valve is exfoliated [20]. Like Hipponicharionidae, the Beyrichonidae have a subtriangular shield [25].…”