Eocrinoid

Wudingeocrinus rarus

• Cambrian
• Wulongqing Formation (Guanshan Biota)
• Yunnan, China

Size: ~4 cm theca+arms

The Guanshan Biota contains one of the earliest known occurrences of Eocrinoids and echinoderms in general in the fossil record. Wudingeocrinus rarus is one of the scarce eocrinoids in this formation that exhibits a combination of rather unusual/primitive traits, namely a complete lack of sutural pores in the theca, a low number of long spiral arms, and most notably an incredibly long, tapering stalk (Hu et al. 2007). The long stalk is occasionally found with kinks and bends (as seen in this specimen) which has been interpreted as an indication of high rigidity, and it has been suggested that Wudingeocrinus secured itself by embedding most of its long stalk into the sediment, as opposed to attaching itself directly to a substrate (Zhao et al. 2022).