The Priapulida

Prior to 1968, the phylum Priapulida was considered to be a cold-water, macrobenthic taxon, represented in the meiofauna only by larval stages. The 7 species and 4 genera were al placed in a single family. Beginning with the discovery of Tubiluchus carallicola from the shallow, warm waters of Curaçao, the number of pripaulid taxa has steadily increased to 15 species, 7 genera, and 3 families. Most (7 species) or all (8 species) of these new taxa are meiofaunal. However, they are not merely miniatures of their larger macrofaunal relatives. They exhibit many new morphological and ecological characters demonstrating that the basic priapulid body plan is much more plastic than it was once thought to be.

The Priapulida are vermiform marine invertebrate, their body is unsegmented, cylindrical, and generally has three body regions: an introvert, abdomen, and tail or caudal appendage. Fourteen of the 15 species of extant priapulids are included in the three families: Chaetostephanidae, Priapulidae and Tubiluchidae. Meiofaunal priapulids include all species of the families Chaetostephanidae and Tubiluchidae and are generally associated with abundant and diverse meiofaunal assemblages. This is in marked contrast to be macrofaunal priapulids which appear to most common in sediments with a poor fauna. Though all meiofaunal priapulids, with the possible exception of the tube-dwelling Maccabeus appear to be active burrowers like the larger macrofaunal species.