| Cephalodiscus | |
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| Cephalodiscus dodecalophus | |
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Class: | |
| Order: | |
| Family: | Harmer, 1905 |
| Genus: | Cephalodiscus M'Intosh, 1882 [1] |
| Type species | |
| Cephalodiscus dodecalophus McIntosh 1882 | |
| Species | |
See text | |
| Synonyms | |
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Cephalodiscus is a genus of hemichordates in the monotypic family Cephalodiscidae of the order Cephalodiscida.
All known species live in a secreted coenecium attached to a rock substrate. [2] Unlike Rhabdopleura , Cephalodiscus species do not form large colonies and are only pseudocolonial, but they do share a common area with individual buds for each zooid. [2] [3] Cephalodiscus zooids are also more mobile than their Rhabdopleura counterparts, and are able to move around within tubaria. Cephalodiscus zooids can be produced via asexual budding. There are a few pairs of tentacled arms, whereas Rhabdopleura has only one pair of arms. [3]
19 living species of Cephalodiscus have been described: [4]
Extinct species include:
Proposed subgenera are idiothecia, demiothecia, orthoecus, and acoelothecia. [2]
The Cephalodisci are endemic to the Antarctic and Southern Ocean, whose relative inaccessibility has historically limited human study of the genus. [2] The Erebus and Terror may have unwittingly encountered C. Nigrescens specimens, and the Challenger C. densus; but until the Swedish Antarctic Expedition of 1901-1903, only C. Dodecalphus had been identified. [5] In 1882, M'Intosh (later spelled McIntosh) had identified Dodecalphus from dredged Magellanic-Straits material, work published 5 years later, but the discovery left cephalodiscid phylogeny unclear. [2] [5] M'Intosh proposed placement amongst the polyzoa, whilst Harmer suggested the modern placement amongst hemichordates. The Swedish expedition provided a plethora of new species, and subsequent researchers began to recognize cephalodiscid species in the relatively temperate waters off South Africa, the Falklands, Sri Lanka, and Australia. At the same time, researchers also determined that C. rarus and andersonii were in fact C. densus specimens. [2]
Cephalodiscus planitectus is the most recently discovered species. It was described in 2020 from specimens found in Sagami Bay off the southern coast of Honshu, Japan. [6]
Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian through the Lower Carboniferous (Mississippian). A possible early graptolite, Chaunograptus, is known from the Middle Cambrian. Recent analyses have favored the idea that the living pterobranch Rhabdopleura represents an extant graptolite which diverged from the rest of the group in the Cambrian. Fossil graptolites and Rhabdopleura share a colony structure of interconnected zooids housed in organic tubes (theca) which have a basic structure of stacked half-rings (fuselli). Most extinct graptolites belong to two major orders: the bush-like sessile Dendroidea and the planktonic, free-floating Graptoloidea. These orders most likely evolved from encrusting pterobranchs similar to Rhabdopleura. Due to their widespread abundance, planktonic lifestyle, and well-traced evolutionary trends, graptoloids in particular are useful index fossils for the Ordovician and Silurian periods.
Cephalodiscida is one of two orders in the class Pterobranchia, which are small, worm-shaped animals. Members belong to the hemichordates. Species in this order are sessile, living in clear water and secrete tubes on the ocean floor.
Jane Stephens was an Irish zoologist who was considered a leading authority on sponges in Ireland with specialised knowledge in other marine life who identified and named over 40 sponges new to science. From 1905 to 1920 she was employed in the Natural History Division of the National Museum of Ireland working primarily on the collections of marine invertebrates, including taking part in the Clare Island Survey. Robert Lloyd Praeger testified to her knowledge of and work with Irish sponges stating that "Most of what we know of this group, whether marine or fresh-water, in Ireland, or off the Irish coasts, is due to her work."
Denis Gascoigne Lillie was a British biologist who participated in the Terra Nova Expedition (1910–1913) to the Antarctic. He collected numerous marine animals as well as plants and fossils–many of which were new to science–and published scientific papers on whales, fossils, and medicine. He received the Polar Medal along with other Terra Nova members in 1913. He was also a noted caricaturist who made cartoons of professors, colleagues, and friends: some of his caricatures are collected in the National Portrait Gallery. He worked as a government bacteriologist during World War I and then suffered a severe mental breakdown, spending three years at Bethlem Royal Hospital and never fully recovering. He is commemorated in the names of several marine organisms as well as Lillie Glacier in Antarctica.
The clade Multicrustacea constitutes the largest superclass of crustaceans, containing approximately four-fifths of all described crustacean species, including crabs, lobsters, crayfish, shrimp, krill, prawns, woodlice, barnacles, copepods, amphipods, mantis shrimp and others. The largest branch of multicrustacea is the class Malacostraca.
Calycophorae is a suborder of Siphonophores alongside two other suborders Physonectae and Cystonectae. This suborder includes the giant siphonophore, ; one of the longest lengthwise extant creatures (40–50m). While the Physonectae have a pneumatophore, nectophore, and a siphosome, Cystonectae lack a nectophore, and Calycophorae lack a pneumatophore. From the bell-shaped nectophores, Physonectae and Calycophorae are called Codonophores or Greek for bell-bearers. The distribution, morphology, and behaviors of Calycophorae species are vast and greatly depend on the species. Calycophoraes typically consist of two nectophores with a siphosome that have many tentacles that grow out of the siphosome. The Calycophoraes move by propelling water out of the nectophore much like how jellyfishes move. The tentacles act as fishing nets where the nematocysts on the tentacles paralyze their prey which are then later fed on. Calycophorae have three life stages, which are the larval development stage, the polygastric stage, and the eudoxid maturation stage. Each Calycophorae colony forms from one fertilized egg.
Cephalodiscus agglutinans is a sessile hemichordate belonging to the order Cephalodiscida.
Cephalodiscus densus is a sessile hemichordate belonging to the order Cephalodiscida. The species is endemic to the Antarctic, being found in the Ross Sea and much of the Antarctic coastline, as well as near the Kerguelen Islands.
Cephalodiscus dodecalophus is a sessile hemichordate belonging to the order Cephalodiscida.
Cephalodiscus evansi is a sessile hemichordate belonging to the order Cephalodiscida.
Cephalodiscus hodgsoni is a sessile hemichordate belonging to the order Cephalodiscida.
Cephalodiscus levinsoni is a sessile hemichordate belonging to the order Cephalodiscida.
Cephalodiscus nigrescens is a sessile hemichordate belonging to the order Cephalodiscida.
Cephalodiscus planitectus is a sessile hemichordate belonging to the order Cephalodiscida.
Cephalodiscus sibogae is a sessile hemichordate belonging to the order Cephalodiscida. Sightings of the species has been reported only once.
Cephalodiscus solidus is a sessile hemichordate belonging to the order Cephalodiscida.
Marphysa is a genus of annelids belonging to the family Eunicidae.
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