Priapulid Worm Fossil with Gut Trace and Proboscis
sp. (Priapulid worm fossil)
Middle Cambrian Utah
Cambrian Explosion Fossils
Size: mm (25.4mm=1
inch): 25mm on 35mm X 50mm matrix
Location: Marjum Formation,
Millard County, Utah
priapulid worm, Selkirkia sp., is a rare fossil in that it has the
gut trace and the proboscis well preserved.
worms are among the fossils found in the Burgess
shale, and ancestors are still extant today, though not diverse.
They are as biologically complex as arthropods, and are thus important
in the Cambrian fossil record. Taxonomically, they belong to a group
named the Cephalorhyncha that are ecdysozoan animals -- encompassing
the arthropods (insects, spiders, and crustaceans) and the nemotodes.
The grouping is based on a set of shared characters including the
presence of a cuticle and the fact that they periodically shed their
cuticle in a process called ecdysis. All cephalorhynchs have a spiny
proboscis that is used to gather food.