The diverse bivalved arthropods of Castle Bank (Darriwilian, Ordovician), Wales

Abstract

The Darriwilian ( Didymograptus murchisoni Biozone, Middle Ordovician) Castle Bank Lagerstätte, near Llandrindod, Wales (UK) hosts a diverse assemblage of marine animals, generally under 10 mm in size. Here we provide an overview of the diversity of bivalved arthropods from Castle Bank. Soft tissues, including anterior grasping appendages and segmented limbless abdomens, can be observed in some specimens, including Ffabach peryglus gen. et sp. nov., and a second species left in open nomenclature. All other recognized species are known only from isolated carapaces, including two caryocaridid species, four ostracode species, a small lightly mineralized carapace preserved in butterfly arrangement ( Gloynia jonesi gen. et sp. nov.), and isolated carapaces of uncertain affinity (five morphs with spines, four morphs without spines). In this contribution 18 distinct taxa are recognized in total, either formally described, left in open nomenclature, or recognized as morphs currently interpreted as distinct species. The caryocaridids include a single specimen assigned to Caryocaris  sp., and two specimens questionably assigned to Ivocaris ? sp.; these three specimens are the first caryocaridids reported from the Builth Inlier. Four podocope ostracode species are recognized: Bullaeferum llandeiloensis , Laterophores  sp., Pariconchoprimitia  sp. and an undetermined podocope. The remaining animals cannot be confidently placed in known taxonomic groups, but probably represent different species due to their distinct carapace outlines and similar size.