A new pygocephalomorph crustacean from the Brymbo Fossil Forest (Moscovian), North Wales, UK and a reassessment of the genus Pygocephalus

The genus Pygocephalus was one of the first groups of eumalacostracan Crustacea to explore and adapt to the new and dynamic freshwater systems created by the Earth’s earliest established rainforest in the Carboniferous. Characterized by a flattened body with a distinct carapace covering the thorax and well-developed pleon, Pygocephalus is regularly recovered from what were the braided rivers of the Carbonifeorus forests of Europe and North America. In this paper a new species of Pygocephalus, Pygocephalus brymboensis sp. nov., is described from the Moscovian of North Wales, primarily distinguished by a carapace that is slightly broader than long, a rostrum equal in length to the carapace and a unique pleural morphology. This study explores the position of P. brymboensis within Pygocephalomorpha and investigates the use of non-carapace-based morphometry as a tool for exploring morphological relationships between related taxa. The description of this species and exploration of the taxonomic history of the genus highlights the need for close examination of historical collections for the identification of subtle morphological differences, particularly in collections primarily amalgamated from multiple geographically disparate ex situ localities.https://zoobank.org/urn:lsid:zoobank.org:pub:8F524CBA-AD15-4478-8150-CFE3C3785BFF