Chthamalus

Chthamalus is a genus of barnacles that is found along almost all coasts of the northern hemisphere, as well as many regions in the southern hemisphere. These small barnacles have been studied in part because of the taxonomic confusion over a group of species that, by and large, are morphologically and ecologically quite similar. In recent years, molecular techniques have identified a number of cryptic species that have been subsequently confirmed by taxonomists using morphological measurements. Most recently the genus has been shown to be paraphyletic, with the genus Microeuraphia nested within Chthamalus.

Field Identification
Identification of barnacles in the field can be challenging, and identification of particular species of Chthamalus is not considered reliable in the field other than a few species. However, a notable distinction in the arrangement of wall plates can help biologists distinguish Chthamalid barnacles from the other common barnacles in the family Balanidae. In chthamalid barnacles, the side plates overlap both the rostrum and the carina (the plates at the ends of the opercular opening), while in balanids one end plate (the rostrum) overlaps the adjoining side plates (rostrolaterals).