Arthropod

Marrella sp.

• Cambrian
• Balang Formation
• Hunan, China

Size: 1.5 cm

This arthropod appears to be the unnamed species of Marrella described from the Balang Formation of China (Liu 2013), which represents the oldest occurrence of the genus. While M. splendens is one of the most common fossils found in the Burgess Shale of Canada, Marrella sp. is rare in the Balang Formation. The primary distinction of the Balang Marrella is supposedly its smooth median cephalic spines (the posterior pair of spines on the headshield), in contrast to the serrated median cephalic spines of M. splendens. That being said, the median cephalic spines on this particular specimen appear to have faint striations and possible serrations. In addition, based on the handful of specimens I have seen, the median cephalic spines on the Balang Marrella seem to be far longer than those of M. splendens; longer than the lateral cephalic spines and even extending well past the end of the body.

The Balang Fm. fossils are preserved in paper-thin calcite wafers, and soft tissue especially can be obscure when present. This particular specimen is one of the best-preserved of its kind that I have seen across its two splits. It exhibits apparent serrations and structure in its four complete sweeping cephalic spines, clear segmentation of the body, several of its delicate swimming appendages and even what appear to be antennae emerging in front of its headshield.