A Jurassic relict of the Triassic stem euryalid brittle star Aspiduriella (Echinodermata, Ophiuroidea)

During recent years, the study of extinct brittle stars has gained significant momentum thanks to advances in our understanding of the groups skeletal morphology. On the basis of these novel insights and the discovery of new, exceptionally preserved material from the middle Hettangian of Belgium, we here re-describe the enigmatic brittle star Mesophiomusium kianiae. We show that it represents a new genus, Persoonaster gen. nov., which shares a number of striking similarities with the Triassic genus Aspiduriella, forming a paedomorphic lineage at the stem of the extant Euryalida for which we here introduce the new family Aspiduriellidae. The Aspiduriella lineage was among the most common and widey disributed in the Triassic, and unexpectedly survived into the Lower Jurassic as evidenced by recognition of the new genus Persoonaster.