Slipped through the bottleneck: Lazarechinus mirabeti gen. et sp. nov., a Paleozoic-like echinoid from the Triassic Muschelkalk (late Anisian) of East France

The unique find of a stem group echinoid with a rotular, flexible corona composed of multiserial ambulacra and interambulacra from the Upper Muschelkalk Calcaire à Entroques (Middle Triassic, late Anisian, late Illyrian) of East France is described. The articulate specimen allows description of all characters besides the apical disc that was lost. The echinoid described as Lazarechinus mirabeti represents a new species and genus of the Carboniferous through Late Permian stem group echinoid family Proterocidaridae. Between the latest Permian proterocidarid Pronechinus and the new Lazarechinus is a gap of approx. 16 Ma covering the Early and early Middle Triassic. This makes the new genus a typical Lazarus taxon belonging to a lineage that disappeared during times of crisis and awoke in times of biotic recovery. Additional references of stem group echinoids are known from the middle Anisian of Southwest China and from the Carnian of Italy and Central China. The new finds provide evidence that the current concepts of echinoid evolution around the Permian–Triassic boundary require thorough reappraisal. The fortunate discovery of Lazarechinus in a Muschelkalk conservation Lagerstätte also encourages the systematic search of isolated sclerites assignable to stem group echinoids in Triassic sediments to provide more information on abundance, distribution, and habitats.