Protocinctus

Protocinctus is a genus of cinctan and, as of 2024^[update], it is the oldest such recognized genus.^[1] It is known from the Wuliuan age of the Mansilla Formation, Zaragoza, Spain.^[2] It is represented by the single species Protocinctus mansillaensis.

Protocinctus Temporal range: Miaolingian (Wuliuan), 506.5–504.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Ventral view of a specimen of Protocinctus mansillaensis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Echinodermata
Class:	†Cincta
Family:	†Sucocystidae
Genus:	†Protocinctus Rahman & Zamora, 2009
Species:	†P. mansillaensis
Binomial name
†Protocinctus mansillaensis Rahman & Zamora, 2009

Description

The genus bears a combination of characters unique to cinctans, with an elongated oval-shaped theca with a single anterior left marginal feeding groove, and a posterior marginal frame open in posterior ventral view.^[2]

Like other cinctans, they would have been active pharyngeal filter feeders. The animal would lay close to the sediment surface with the anterior region oriented downstream and generate an inhalant flow of water directing suspended food particles to the mouth.^[3]