Thoracica is an infraclass of crustaceans which contains the most familiar species of barnacles found on rocky coasts, such as Semibalanus balanoides and Chthamalus stellatus. They have six well-developed limbs, and may be either stalked or sessile. The carapace is heavily calcified. The group includes free-living and commensal species.
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 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 family includes at least 56 recognized species.
Acorn barnacle and acorn shell are vernacular names for certain types of stalkless barnacles, generally excluding stalked or gooseneck barnacles. As adults they are typically cone-shaped, symmetrical, and attached to rocks or other fixed objects in the ocean. Members of the barnacle order Balanomorpha are often called acorn barnacles.
Chthamalus 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.
Chthamalus stellatus, common name Poli's stellate barnacle, is a species of acorn barnacle common on rocky shores in South West England, Ireland, and Southern Europe. It is named after Giuseppe Saverio Poli.
Notochthamalus scabrosus, the only species in the genus Notochthamalus, is a species of barnacle found along the south-western and south-eastern coasts of South America, from Peru to the Falkland Islands. The species is found almost exclusively higher in the intertidal zone than the mussel Perumytilus, often codistributed with the confamilial barnacle Jehlius cirratus and Balanus flosculus.
Megabalanus tintinnabulum is a species of large barnacle in the family Balanidae. It is the type species of the genus. The specific name comes from the Latin tintinnabulum meaning a handbell and probably refers to the fact that small groups of barnacles resemble clusters of miniature bells.
The Chthamaloidea are a subdivision of Balanomorpha proposed by Newman and Ross to include barnacles with shell wall composed of rostrum, carina, and one to three pairs of latera, rarely supplemented with one or more whorls of basal imbricating plates. The rostrolatus enters the sheath, but rarely fuses with the rostrum, as in the three higher superfamilies. Shell plates are simple in construction, solid, and incorporate organic chitin between carbonate layers. Opercular plates are deeply interlocked, and in some genera, may become concrescent with age. Soft part morphology includes concave labrum without notch in the central part. Cirrus III more resembles Cirrus IV than II, or may be intermediate in structure. Caudal appendages present in some species.
Pseudoctomeris sulcatus is a species of barnacle, the only member of the genus Pseudoctomeris. It has an eight-plated shell wall with the rostrum partially fused with adjacent rostrolatera. The suture lines are visible only from the inside, thus in exterior view, the shell appears to have six wall plates. The basis is calcareous. Opercular plates are higher than wide, and not deeply articulated. These features and others show strong relationship to family Pachylasmatidae, and taxonomic revision of Pachylasmatidae has resulted in the transfer of Pseudoctomeris from Chthamalidae to Pachylasmatidae.
The Catophragmidae are a family of barnacles in the superfamily Chthamaloidea with eight shell wall plates, surrounded by several whorls of imbricating plates. The basis is membranous.
Catomerus is a monotypic genus of intertidal/shallow water acorn barnacle that is found in warm temperate waters of Australia. The genus and species is very easily identified by whorls of small plates surrounding the base of the primary shell wall; no other shoreline barnacle species in the Southern Hemisphere has that feature. This species is considered to be a relic, as these plates are found only in primitive living lineages of acorn barnacles or in older fossil species. The fact that this is an intertidal species is unusual, because living primitive relic species are often found in more isolated habitats such as deep ocean basins and abyssal hydrothermal vents.
Catolasmus is one of two monotypic Catophragmid acorn barnacle genera recognized in the Northern Hemisphere. It is easily identified by its prominent whorls of imbricating plates surrounding the main wall plates. It is quite large, attaining 55 mm diameter. Catolasmus represents one of the relictual lineages of the basal balanomorph radiation.
Catophragmus is the originally named genus of the family Catophragmidae. At present, it is monotypical. It is a shallow water acorn barnacle of the Tropical Western Atlantic and Caribbean characterized by small accessory imbricating plates surrounding the base of the shell wall.
Chamaesipho is a genus of four-plated notochthamaline barnacles in the Pacific Ocean limited to Australian/New Zealand temperate waters. They are intertidal in preference, and tend to form crowded columnar colonies. They can be identified in the field by having a four-plated wall, an unfused rostrum, and narrow opercular plates. Elminius, which also inhabits the same area, has four plates in its shell wall. However, in Elminius, the rostrum and rostrolatera are fused completely, and the compound rostrum receives the alae of the adjacent carinolaterals. In Chamaesipho, the unfused rostrum bears alae, and closely resembles the carina in appearance.
Chamaesipho brunnea is an intertidal barnacle common in New Zealand, in both the North Island and the South Island. Juveniles have six shell wall plates, reducing to four in adults, and with age, all plates become concrescent, with no trace of sutures inside or out. Shell is brown colored. The related, and sometimes associated Chamaesipho columna is much smaller in size, by nearly half, while Elminius, which can associate with both species, also has four shell wall plates, but plates remain distinct at all stages. The shell of C. columna corrodes to a pitted surface, while that of C. brunnea has a lamellar corrosion.
Chamaesipho tasmanica is an intertidal shoreline barnacle of Australia. Its principal range centers in New South Wales, and Tasmania. Columnar colonies can be found on high intertidal rocks relatively free of dense seaweed. Individuals are small, less than 15 mm, and grayish in color.
Chamaesipho columna is the type species for the barnacle genus Chamaesipho. Originally, species concept, as refined by Darwin472 consisted of C. columna. Spengler's 1790 description included specimens from "Otaheite" (Tahiti), which were far larger than any of the three described species. As Chamaesipho is restricted to Australia and New Zealand, and Spengler's Tahiti material lacked opercular plates, it is no longer included as Chamaesipho. Spengler's written description agrees with Chamaesipho.472 Spengler's Tahiti material is thought to be New Zealand Epopella, mislabeled.
Chamaesipho grebneffi is the first extinct member of the Notochthamalinae to be described, and the oldest chthamaloid barnacle known. This species is a fully derived Chamaesipho, and indicates a considerable antiquity for Chthamaloidea.
Rehderella is an unusual and monotypic barnacle genus restricted to Easter Island and Pitcairn Island. Rehderella belyaevi is its only species.
