Chthamalus (χθαμαλός, "flat" or "on the ground") is a genus of barnacles that is found along almost all non-boreal 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.

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