Skioldia aldna, an Unusual Arthropod from Chengjiang
"Part and Counterpart"

Description: This unusual arthropod is known as Skioldia aldna. The species is known from only a few examples as of 2004, some of which are as much as 100 mm in length. With the discovery of the Chengjiang Biota in 1984 a window on the Cambrain Explosion in China was opened. 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 taxon bears some resemblance to the younger Burgess Shale genus Helmetia, which has led some to place them in the Helmetidae along with several other similar arthropods. It has currently, however, been assigned its own family, Skioldiae. The body shape suggests that like the similar taxon Kuamaia it was a benthic animal which was possibly carnivorous. Unlike Kuamaia, Skioldia had much less distinct segmentation. The central digestive system is the most distinct feature seen on this exceptionally rare specimen. The larger part almost assuredly has additional material preserved under the matrix. The species is only known from the Chengjiang Biota.