NEKTASPIDID ARTHROPODS FROM THE EARLY ORDOVICIAN FEZOUATA BIOTA, MOROCCO

Nektaspidida are an Order of non-biomineralized Early Paleozoic lamellipedian arthropods, which includes the Families Naraoiidae, Liwiidae and Emucarididae. While the appendages of several naraoiid taxa are known in considerable detail, outside of the antennae in Liwia plana, no appendages are known in liwiids, and understanding of the appendage morphology of emucaridids is limited. As a result, Nektaspidida is essentially united on potentially plesiomorphic similarities in dorsal exoskeletal morphology, with all taxa being characterized by the possession of large cephalic and tail shields. In Naraoiidae, no free thoracic tergites are present, while both liwiids and emucaridids exhibit a short thorax comprised of three or four free tergites. Although often regarded as ‘soft-bodied trilobites’, nektaspidids consistently fail to resolve within Trilobita in cladistic analyses; while closely related to trilobites, their exact relationship to this clade currently remains unresolved. In fact, considering the lack of robust synapomorphies uniting Nektaspidida, the possibility that the group itself may not represent a monophyletic clade currently cannot be excluded. Nektaspidids are a rare component of the exceptionally preserved Fezouata Biota from the Early Ordovician of south-eastern Morocco. A small liwiid with an elongate cephalic shield overlapping the first of three trunk tergites and a tail shield of comparable shape but smaller size is known from three different instars. While naraoiids are a typical component of many Cambrian Burgess Shale-type faunas, in the Fezouata Biota they are so far only represented by a single, poorly preserved and incomplete specimen. These new finds add to the scarce Ordovician record of Nektaspidida, which until now was limited to the Middle Ordovician naraoiid Pseudonaraoia hammanni from the Czech Republic and the Late Ordovician liwiids Tariccoia arrusensis from Sardinia and Soomaspis splendida from South Africa.