Presence of Eodiscida (Trilobita) in the Cambrian Series 2 of the Iberian Chains (Northeast Spain)

The Cambrian Series 2 of the Iberian Peninsula is characterised by strong trilobite faunal endemism, which has hindered both regional and intercontinental correlations. In the Iberian Chains (Northeast Spain), the Marianian regional stage deposits of the Ribota and Huérmeda formations contain a trilobite fauna that is still insufficiently studied, despite its considerable biostratigraphic potential. This study documents the occurrence of the globally distributed Eodiscida in the lower part of the Huérmeda Formation (upper Marianian; base of the Stage 4 of the Cambrian). Morphometric analyses of cranidial shape demonstrate that specimens previously tentatively assigned to Hebediscus represent a new species, Hebediscus carlsi n. sp. Additional material from the same horizon is tentatively assigned to Hebediscina , constituting the first record of this genus in the Iberian Peninsula. The presence of Hebediscus and Hebediscina provides a robust basis for correlating the lower part of the Huérmeda Formation with coeval horizons in the West Gondwana margin, Avalonia, Siberia, Central Asian Orogenic Belt, and Australia, contributing to improved regional and intercontinental correlation of Cambrian Series 2 strata.