Redescription and interpretation of the asteroid species Tropidaster pectinatus from the Jurassic of England

Tropidaster pectinatus is redescribed based on the original collection from Lower Jurassic (Pliensbachian) strata of England. It is the only recognized member of the Tropidasteridae, which is assigned to the Order Velatida in an intermediate phylogenetic position between the extant families Solasteridae, the earliest known representative of which is from Middle Jurassic (Bathonian) strata and considered primitive in the order, and the Korethrasteridae, known only from Holocene species. Surviving asteroids have been separated into three superorders; all are recognized from strata of Early Jurassic age, and Tropidaster provides additional evidence for the early diversification of extant asteroids. Based on arm curling and robust disc construction, Tropidaster might have been a selective predator.