Temporal range: Lower Pennsylvanian–Recent
J. Yager 1981
|Orders & families|
Remipedia is a class of blind crustaceans found in coastal aquifers which contain saline groundwater, with populations identified in almost every ocean basin so far explored, including in Australia, the Caribbean Sea, and the Atlantic Ocean. The first described remipede was the fossil Tesnusocaris goldichi (Lower Pennsylvanian). Since 1979, at least seventeen living species have been identified in subtropical regions around the world.
Remipedes are 1–4 centimetres (0.4–1.6 in) long and comprise a head and an elongate trunk of up to thirty-two similar body segments. They lack eyes and pigmentation. Biramous swimming appendages are laterally present on each segment, and the animals swim on their backs. They are generally slow-moving. They are the only known venomous crustaceans, and have fangs connected to secretory glands, which inject a combination of digestive enzymes and venom into their prey.
Remipedia have a generally primitive body plan compared to other extant crustaceans, and are the only extant pancrustaceans to lack significant postcephalic tagmosis.Previously regarded as 'primitive', remipedia have since been shown to have enhanced olfactory nerve centers (a common feature for species that live in dark environments).
The class Remipedia was erected in 1981 by Jill Yager, in describing Speleonectes lucayensis from the Bahamas.The name "Remipedia" is from the Latin remipedes, meaning "oar-footed".
Historical phylogeny based on morphology and physiology has placed Remipedia under Mandibulata, in the subphylum Crustacea, and distinct from Hexapoda.
New research in evolution and development reveals similarities between larvae and postembryonic development of remipedes and Malacostraca, singling Remipedia as a potential crustacean sister group of Hexapoda. Similarities in brain anatomy further support this affinity, and hexapod-type hemocyanins have been discovered in remipedes.
Recent analysis based on nuclear protein-coding genes implies that remipedes (along with Cephalocarida) are the sister group of arthropods most closely related to insects. Remipedia and Cephalocarida are grouped together form the clade Xenocarida.The extant lineages Xenocarida, Vericrustacia, Oligostraca, and Hexapoda together form the proposed class Pancrustacea. The clade Miracrustacea ('surprising crustaceans') has been proposed for the monophyletic clade containing xenocarids and hexapods.
|Phylogenetic position of Remipedia within Pancrustacea|
This section needs to be updated. In particular: more species and families - see World Remipedia Database.February 2016)(
Twenty eight extant species are recognized as of early 2016, divided among eight families and twelve genera.All are placed in the order Nectiopoda. The second order, Enantiopoda, comprises the fossil species Tesnusocaris goldichi and Cryptocaris hootchi .
Branchiopoda is a class of crustaceans. It comprises fairy shrimp, clam shrimp, Cladocera, Notostraca and the Devonian Lepidocaris. They are mostly small, freshwater animals that feed on plankton and detritus.
Malacostraca is the largest of the six classes of crustaceans, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crabs, lobsters, crayfish, shrimp, krill, woodlice, amphipods, mantis shrimp and many other, less familiar animals. They are abundant in all marine environments and have colonised freshwater and terrestrial habitats. They are segmented animals, united by a common body plan comprising 20 body segments, and divided into a head, thorax, and abdomen.
The Stenopodidea is a small group of decapod crustaceans. Often confused with shrimp or prawns, they are neither, but belong in a group closer to the reptant decapods, such as lobsters and crabs. They may be easily recognised by their third pereiopod, which is greatly enlarged. In the lobsters and crabs, it is the first pereiopod that is much bigger than the others. There are 71 extant species currently recognised, divided into 12 genera. Three fossil species are also recognised, each belonging to a separate genus. The earliest fossil assigned to the Stenopodidea is Devonostenopus pennsylvaniensis from the Devonian. Until D. pennsylvaniensis was discovered, the oldest known member of the group was Jilinicaris chinensis from the Late Cretaceous.
Tesnusocaris goldichi is an extinct species of remipedian crustacean that lived in the Pennsylvanian period, the one of the two representatives of the extinct remipedian Order Enantiopoda. Its fossil is from the Lower Pennsylvanian Tesnus formation, Texas. The other known enantiopod remipedian is Cryptocaris hootchi of the Mazon Creek fauna.
Atelocerata is a proposed clade of arthropods that includes Hexapoda and Myriapoda, but excludes Crustacea and Chelicerata. The name is currently used interchangeably with Tracheata. or Uniramia sensu stricto. It is an extensive division of arthropods comprising all those that breathe by tracheae, as distinguished from Crustacea, which breathe by means of gills.
Pancrustacea is a clade, comprising all crustaceans and hexapods. This grouping is contrary to the Atelocerata hypothesis, in which Myriapoda and Hexapoda are sister taxa, and Crustacea are only more distantly related. As of 2010, the Pancrustacea taxon is considered well-accepted. The clade has also been called Tetraconata, referring to having four cone cells in the ommatidia. That name is preferred by some scientists as a means of avoiding confusion with the use of "pan-" to indicate a clade that includes a crown group and all of its stem group representatives.
Thermosbaenacea is a group of crustaceans that live in thermal springs in fresh water, brackish water and anchialine habitats. They have occasionally been treated as a distinct superorder (Pancarida), but are generally considered to belong to the Peracarida. Due to their troglobitic lifestyle, thermosbaenaceans lack visual pigments and are therefore blind.
Speleonectidae is a family of remipedes in the order Nectiopoda. There are at least two genera and about seven described species in Speleonectidae.
Godzilliidae is a family of remipedes in the order Nectiopoda. There are at least two genera and four described species in Godzilliidae.
Mandibulata, termed "mandibulates", is a clade of arthropods that comprises the extant subphyla Myriapoda, Crustacea and Hexapoda. Mandibulata is currently believed to be the sister group of the clade Arachnomorpha, which comprises the rest of arthropods. The mandibulates constitute the largest and most varied arthropod group.
Speleonectes atlantida is a species of eyeless crustacean in the order Nectiopoda. It was discovered in August 2009 in the Tunnel de la Atlantida, the world's longest submarine lava tube on Lanzarote in the Canary Islands off the west coast of North Africa. Like other remipedes, the species is equipped with venomous fangs.
Xenocarida is a clade long misplaced inside the subphylum Crustacea that comprises two classes that were discovered in the 20th century: Remipedia and Cephalocarida. Xenocarida is now thought to be the sister clade to Hexapoda.
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult, and there are still cases where it is not known what larvae will grow into what adults. This is especially true of crustaceans which live as benthic adults, more-so than where the larvae are planktonic, and thereby easily caught.
Godzilliognomus schrami is a species of Remipedia discovered in 2007, representing one of five extant species of the family Godzilliidae. It generally reaches about 7 millimetres (0.28 in) in length and inhabits a single anchialine cave on Eleuthera Island. The specific epithet commemorates Frederick Schram.
Lepidocaris rhyniensis is an extinct species of crustacean. It is the only species known from the order Lipostraca, and is the only abundant animal in the Rhynie chert deposits. It resembles modern Anostraca, to which it is probably closely related, although its relationships to other orders remain unclear. The body is 3 mm (0.12 in) long, with 23 body segments and 19 pairs of appendages, but no carapace. It occurred chiefly among charophytes, probably in alkaline temporary pools.
The subphylum Hexapoda constitutes the largest number of species of arthropods and includes the insects as well as three much smaller groups of wingless arthropods: Collembola, Protura, and Diplura. The Collembola are very abundant in terrestrial environments. Hexapods are named for their most distinctive feature: a consolidated thorax with three pairs of legs. Most other arthropods have more than three pairs of legs.
Crustaceans form a large, diverse arthropod taxon which includes such animals as crabs, lobsters, crayfish, shrimps, prawns, krill, woodlice, and barnacles. The crustacean group is usually treated as a class under subphylum Mandibulata and because of recent molecular studies it is now well accepted that the crustacean group is paraphyletic, and comprises all animals in the Pancrustacea clade other than hexapods. Some crustaceans are more closely related to insects and other hexapods than they are to certain other crustaceans.
Xibalbanus tulumensis is a venomous, hermaphroditic crustacean found in anchialine caves on the Yucatán Peninsula in the Caribbean Sea. This blind remipede liquefies the body contents of other crustaceans with a venom similar to that of rattlesnakes, and which includes digestive enzymes and a paralysing toxin.
Pleomothra is a genus of crustacean found in the Caribbean. First described in 1989, the genus has 2 identified species as of 2008 and is one of three genera in the family Godzilliidae.
The clade Multicrustacea constitutes the largest superclass of crustaceans, containing approximately four-fifths of all described crustacean species, including crabs, lobsters, shrimps, woodlice, prawns, krill, barnacles, crayfish, copepods, amphipods and others. The largest branch of multicrustacea is the class Malacostraca.