Description

Plasiacystis sp.
Early Ordovician (Arenigian)
Fezouata Formation
Mecissi-Zagora Region, Draa Valley, Morocco.

Echinoderm.

Very strange flat-tailed carpoid. 46mm on 95mm slab. The unusual tail has led many people to suggest this creature is anything from a vertebrate to a cephalopod, but we found this paper by Prokop that seems to be an excellent match for this still undescribed echinoderm:

Prokop, R. J., & V. Petr. (2003).
Plasiacystis mobilis, gen. et sp. n., a strange “carpoid” (Echinodermata,? Homoiostelea: Soluta) in the Bohemian Ordovician (Czech Republic). Sbornik Narodniho Muzea, Serie B, Prirodni vedy, 59, 151-162.

What is a carpoid? This article explains them (PDF)