Pholadomyida is an order of . There are 2 species of Pholadomyida, in 1 genus and 1 family. This order has been around since the ordovician period. They are facultatively mobile 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)