The Chthamalidae are a family of chthamaloid barnacles, living entirely in intertidal/subtidal habitats, characterized by a primary shell wall of eight, six, or four plates, lacking imbricating plate whorls, and either membraneous or more rarely calcareous basis. They are not be found below immediate subtidal habitats, and more likely are found in the highest tier of shallow-water barnacle fauna. They can be found in the most rigorous wave-washed locations, and some species are found in the surf zone above high tide mark, only receiving water from wave action at high tide.
The shell wall consists of eight wall plates, which reduce to six, and four in some species. Plate reduction is accomplished by fusion of rostrolatera with adjacent laterals, or initially by suppression of carinolatus II, reducing plate number from eight to six. Unlike the superfamilies Coronuloidea and Balanoidea, the rostrum rarely fuses with rostrolatus. In soft parts, caudal appendages are rare, and the mandible usually has three or our teeth, rarely five, and frequently bears fine bristles.:65 Cirri I and II, sometimes III, bear specialized setae to comb net-forming cirri for food particles. These are termed comb setae, which are thin spines bearing fine bristles, and card setae:332 (also known as grapple setae). Card setae are grapple-like or wool carder-like in appearance.
The other chthamaloid family, Catophragmidae, differs from Chthamalidae in possessing whorls of imbricating basal plates. In field work, this is the easiest characteristic to observe.
Taxonomic classification of chthamalid barnacles has proven challenging because of the preferred environment, resulting in convergence of shell and opercular form. Characters used in classification are weighted heavily to soft part morphology. As this requires time and specialized equipment, effort is made in this project to aid identification for field and biodiversity surveyors. Usually, any given region harbors less than three chthamalid species, which will usually concentrate to preferred microhabitats. Becoming familiar with what should be expected in each area narrows the range of species dramatically. Then, unusual finds can be spotted and sampled for further lab study.
DNA and cytochrome enzyme analyses have proved promising in uncovering cryptic species populations. These studies are still effectively in their early stages.
Members of the Chthamalidae are found in all oceans except the Arctic Ocean, in temperate and tropical zones. They prefer intertidal marine habitats, from lower littoral to upper surf zone, uncommonly sublittoral. All are known from normal marine salinity.:65 Several genera are monotypic. Some of these appear to be relictual, others are speciations on oceanic islands.
^Darwin, Charles (1854). A monograph on the sub-class Cirripedia with figures of all species. The Balanidae, the Verrucidae, etc. London: Ray Society. pp. 1–684.
^ abcdPoltarukha, O. P. (2006). Identification Atlas of barnacles (Cirripedia Thoracica) of the Superfamily Chthamaloidea in the world ocean. Moscow: KMK Scientific Press, Ltd. pp. 1–198 In Russian. ISBN5-87317-278-1.
Barcode of Life Data Systems (BOLD) Stats Specimen Records:2892 Specimens with Sequences:2868 Specimens with Barcodes:2739 Species:45 Species With Barcodes:45 Public Records:2806 Public Species:42 Public BINs:63