Asteriacites von Schlotheim, 1820 – the oldest valid ichnogenus name – and other asterozoan-produced trace fossils

The ichnogenus Asteriacites von Schlotheim, 1820 results from the resting activity of sea stars (Asteroidea) and brittle stars (Ophiuroidea) and is a common cosmopolitan trace fossil recorded from the Cambrian to the Quaternary. Its taxonomic validity has recently been challenged because of the lack of type material, but newly discovered specimens from the von Schlotheim collection in the Natural History Museum (Museum für Naturkunde) of Berlin justify the validity of this ichnotaxon and thus make it the oldest valid ichnogenus name. The ichnofamily Asteriacitidae nov. is established for radial imprints and shallowly excavated pits and contains the ichnogenera Asteriacites (type ichnogenus), Asterichnites Brown and Vokes, 1944, and Ichnocumulus Seilacher, 1956. Basic morphology is regarded as the main ichnotaxobase for distinction of ichnogenera, while overall morphology in combination with morphometry (e.g. length/width ratio of arm imprints) aids the distinction of ichnospecies. Consequently, three Asteriacites ichnospecies can be differentiated, which are (with decreasing length/width ratio of their arm imprints) A. lumbricalis von Schlotheim, 1820; A. stelliformis (Miller and Dyer, 1878) Osgood, 1970; and A. quinquefolius (Quenstedt, 1876) Seilacher, 1953. Moreover, arcuate or hook-shaped imprints occurring isolated or clustered (e.g. trackways) are assigned to the ichnofamily Biformitidae nov., containing Biformites Linck, 1949 (type ichnogenus); Arcichnus Sutcliffe, 1997; and Harpichnus Vallon et al., 2015 (produced by moulting of arthropods). Burrows attributed to asterozoan activity are briefly mentioned.