Akentrogonida is an order of . There are 18 species of Akentrogonida, in 8 genera and 5 families. This order has been around since the priabonian age. They are sessile animals.
Definition: The number of fossil occurrences in the Paleobiology Database (https://paleobiodb.org) that are identified as belonging to a particular taxon or any of its subtaxa.
Definition: A group of species that exploit the same food resources, and/or use the same feeding or foraging methods. http://en.wikipedia.org/wiki/Guild_(ecology)
Definition: An eye that consists of a cluster of three or four pit eyes that form a single structural unit but are separated from one another by pigment layers