Detailed Rare Ercaicunia multinodosa, an Arthropod from Chengjiang

Description: This unusual arthropod is known as Ercaicunia multinodosa. The species is known mostly from the thin-shelled carapace, with this one showing both the segmented abdomen, and the tail fan, seen here in dorsal aspect. The diversity of soft-tissue fossils is astonishing: algae, medusiforms, sponges, priapulids, annelid-like worms, echinoderms, arthropods (including trilobites), hemichordates, chordates, and the first agnathan fish make up just a small fraction of the total. Numerous problematic forms are known as well, some of which may have represented failed attempts at diversity that did not persist to the present day.

The systematic position of this taxon has undergone several revisions. It was established as the sole member of the Family Clypercarididae, and was originally known from only one specimen. Those from Chengjiang have been called Ercaicunia multinodosa, but some scientists believe that to be a junior synonym of Clypecaris. It differs from the more common genus Waptia in having a higher number of body segments.