A new species of Soomaspis (Naraoiidae) from the Upper Ordovician of Bohemia

The family Naraoiidae represents Lower Paleozoic artiopodan euarthropods with non-biomineralized exoskeletons that are particularly abundant in Cambrian Konservat-Lagerstätten. Despite this early abundance, they are much rarer in post-Cambrian deposits. Soomaspis splendida Fortey & Theron, 1994, one of the few known Ordovician species, was described from the Hirnantian Soom Shale Member of the Cedarberg Formation, South Africa. This naraoiid is characterized by a circular, featureless cephalon, three thoracic tergites, and a pygidium with five pairs of interpleural furrows. Here we describe a new species of Soomaspis – Soomaspis labutai sp. nov. – from the Katian Králův Dvůr Formation of the Prague Basin (Czech Republic), based on a single specimen recovered from the recent construction of a new metro line in Prague. Soomaspis labutai sp. nov. is distinguished from S. splendida by its proportionally shorter pygidium and different exoskeletal sculpture. The occurrence of Soomaspis in Bohemia demonstrates that this genus was present along the Gondwanan margin prior to the Hirnantian glaciation and survived both pulses of the end-Ordovician mass extinction. Soomaspis distribution in two geographically distant regions, coupled with its occurrence in high-latitude settings, indicates a broader paleogeographic and ecological distribution than previously recognized. The new species also demonstrates that naraoiids were more widespread during the Ordovician than the current fossil record implies.