Hurdiids
Hurdiidae are an extinct cosmopolitan family of radiodonts, a group of stem-group arthropods, lasting from the Cambrian to the Devonian. Hurdiidae is characterized by the frontal appendages. The family includes Schinderhannes bartelsi, Peytoia nathorsti, Aegirocassis benmoulae, Hurdia victoria,Stanleycaris hirpex, Hurdia triangulata and Buccaspinea cooperi.