Sicyophorus rarus, Diminutive Priapulid Worm from Chengjiang

Description: This is one of the more rare members of the Priapulida is known as Sicyophorus rarus. 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 priapulids are a group of non-segmented worms whose modern-day examples can reach 30 cm in length, and live in both shallow and deep marine sands as carnivores. Individuals of this small taxon, much like Palaeopriapulites parvus (parvus means “small” in Latin), are less than 10 mm in length with a figure 8 shape. This one possesses a coiled gut nor seen in P. parvus. Some researchers believe that S. rarus is a junior synonym of Protopriapulites haikouensis.