ODD COUPLE Chengjiang Maotianshan Shales Fossils Association

Description: This piece shows an unusual association of two members of the Chengjiang Biota. The top specimen is an enigmatic creature known as Eldonia eumorpha. The species is known from numerous specimens, and is one of the largest animals, sometimes in excess of 100 mm across. This one is quite small at less than 10% of maximum size. Specimens are preserved as a nearly flat impression. Distinct strands radiating from the center are interpreted as radial canals on both the ventral and dorsal surface. The unusual arthropod (below) is known as Ercaicunia multinodosa, seen here in lateral view. The species is known mostly from the thin-shelled carapace. This one, however, shows most all of the body with the shells less distinct.

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 while others place Clypecaris as a separate genus. It differs from the more common genus Waptia in having a higher number of body segments.