Time: Early Cambrian, (~525 million years ago)
mm = 1 inch): Eldonia: 10 mm across Ercaicunia: 9 mm long by 4 mm wide
a 45 mm by 65 mm matrix
Site: Chengjiang Maotianshan Shales, Quiongzhusi Section, Yu’anshan
Member, Heilinpu Formation, Mafang Village, Anning, Kunming, Yunnan Province,
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
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
systematic position of this taxon has undergone several revisions.
It was established as the sole member of the Family
and was originally known from only one specimen. Those from Chengjiang
have been called Ercaicunia multinodosa, but some scientists
that to be a junior synonym of Clypecaris while others place
Clypecaris as a separate genus. It differs from the more common
in having a higher number of body segments.