The trilobite Serrodiscus Richter & Richter from Iberia, with systematic review of the genus and its international correlation through the Cambrian Series 2

Serrodiscus is considered one of the first trilobite genera showing global distribution during the Cambrian and a key component for the international correlation of this period. However, this genus encompasses many poorly documented species, ambiguous diagnoses or characters that depend on taphonomy and deformation based on one single specimen. Thus, in the present work, we carry out a systematic overview of the genus, evaluating the taphonomic and deformational variability of a large number of specimens from the same locality and horizon. In addition, and due to the difficulty of making synonymy decisions, closely related species are grouped into three different groups taking into consideration morphologic, stratigraphic and palaeobiogeographic data: bellimarginatus group, scattered along Avalonian and western Gondwanan margins; speciosus group, extending over the Laurentian domain; and daedalus group, being restricted to eastern Gondwana (Australia), North China and, partially, Siberia. Besides, the regional correlation through the early Cambrian of Iberia is arranged, describing specimens from both Ossa-Morena and Central Iberian zones, with a time interval restricted to the upper Marianian Stage. Regarding the biostratigraphy and palaeobiogeography of the genus, Serrodiscus has been reported from Laurentia, Taconic Allochthon, Greenland, Baltica, western and eastern Avalonia, western Gondwana margin, Siberia, North China and eastern Gondwana, with a temporal distribution along with the Cambrian Series 2.