Coelacanth

The coelacanths (/ˈsiːləkænθ/ (listen) SEE-lə-kanth) constitute a now-rare order of fish that includes two extant species in the genus Latimeria: the West Indian Ocean coelacanth (Latimeria chalumnae) primarily found near the Comoro Islands off the east coast of Africa and the Indonesian coelacanth (Latimeria menadoensis).[2] They follow the oldest-known living lineage of Sarcopterygii (lobe-finned fish and tetrapods), which means they are more closely related to lungfish and tetrapods than to ray-finned fishes. They are found along the coastlines of the Indian Ocean and Indonesia.[3][4] The West Indian Ocean coelacanth is a critically endangered species.

Coelacanths belong to the subclass Actinistia, a group of lobed-finned fish related to lungfish and certain extinct Devonian fish such as osteolepiforms, porolepiforms, rhizodonts, and Panderichthys.[5] Coelacanths were thought to have become extinct in the Late Cretaceous, around 66 million years ago, but were rediscovered in 1938 off the coast of South Africa.[6][7]

The coelacanth was long considered a "living fossil" because scientists thought it was the sole remaining member of a taxon otherwise known only from fossils, with no close relations alive,[5] and that it evolved into roughly its current form approximately 400 million years ago.[1] However, several recent studies have shown that coelacanth body shapes are much more diverse than previously thought.[8][9][10]

Coelacanths
Temporal range:
Early Devonian-Holocene,[1] 409–0 Ma
Latimeria Chalumnae - Coelacanth - NHMW
Preserved specimen of West Indian Ocean coelacanth caught in 1974 off Salimani, Grand Comoro, Comoro Islands
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subclass: Actinistia
Order: Coelacanthiformes
L. S. Berg, 1937
Families and unplaced genera

Etymology

The word Coelacanth is an adaptation of the Modern Latin Cœlacanthus ("hollow spine"), from the Greek κοῖλ-ος (koilos "hollow" + ἄκανθ-α akantha "spine"). It is a common name for the oldest living line of Sarcopterygii,[11] referring to the hollow caudal fin rays of the first fossil specimen described and named by Louis Agassiz in 1839.[5] The genus name Latimeria commemorates Marjorie Courtenay-Latimer who discovered the first specimen in a fish market.[12]

Discovery

The coelacanth, which is related to lungfishes and tetrapods, was believed to have been extinct since the end of the Cretaceous period.[13] More closely related to tetrapods than to the ray-finned fish, coelacanths were considered transitional species between fish and tetrapods.[14] On 23 December 1938, the first Latimeria specimen was found off the east coast of South Africa, off the Chalumna River (now Tyolomnqa).[6][15] Museum curator Marjorie Courtenay-Latimer discovered the fish among the catch of a local angler, Captain Hendrick Goosen.[6][15] Latimer contacted a Rhodes University ichthyologist, J. L. B. Smith, sending him drawings of the fish, and he confirmed the fish's importance with a famous cable: "MOST IMPORTANT PRESERVE SKELETON AND GILLS = FISH DESCRIBED."[6][15]

Its discovery 66 million years after it was believed to have become extinct makes the coelacanth the best-known example of a Lazarus taxon, an evolutionary line that seems to have disappeared from the fossil record only to reappear much later. Since 1938, West Indian Ocean coelacanth have been found in the Comoros, Kenya, Tanzania, Mozambique, Madagascar, and in iSimangaliso Wetland Park, Kwazulu-Natal in South Africa.[16]

The Comoro Islands specimen was discovered in December 1952.[17] Between 1938 and 1975, 84 specimens were caught and recorded.[18]

The second extant species, Indonesian coelacanth, was described from Manado, North Sulawesi, Indonesia in 1999 by Pouyaud et al.[19] based on a specimen discovered by Mark V. Erdmann in 1998[20] and deposited at the Indonesian Institute of Sciences (LIPI).[21] Erdmann and his wife Arnaz Mehta first encountered a specimen at a local market in September 1997, but took only a few photographs of the first specimen of this species before it was sold. After confirming that it was a unique discovery, Erdmann returned to Sulawesi in November 1997 to interview fishermen to look for further examples. A second specimen was caught by a fisherman in July 1998 and it was then handed to Erdmann.[22][23]

The coelacanth has no real commercial value apart from being coveted by museums and private collectors. As a food fish it is almost worthless, as its tissues exude oils that give the flesh a foul flavor.[24] The coelacanth's continued survival may be threatened by commercial deep-sea trawling,[25] in which coelacanths are caught as bycatch.

Physical description

Latimeria menadoensis
Preserved Latimeria menadoensis, Tokyo Sea Life Park, Japan

Coelacanths are a part of the clade Sarcopterygii, or the lobe-finned fishes. Externally, several characteristics distinguish the coelacanth from other lobe-finned fish. They possess a three-lobed caudal fin, also called a trilobate fin or a diphycercal tail. A secondary tail extending past the primary tail separates the upper and lower halves of the coelacanth. Cosmoid scales act as thick armor to protect the coelacanth's exterior. Several internal traits also aid in differentiating coelacanths from other lobe-finned fish. At the back of the skull, the coelacanth possesses a hinge, the intracranial joint, which allows it to open its mouth extremely wide. Coelacanths also retain an oil-filled notochord, a hollow, pressurized tube which is replaced by the vertebral column early in embryonic development in most other vertebrates.[26] The coelacanth heart is shaped differently from that of most modern fish, with its chambers arranged in a straight tube. The coelacanth braincase is 98.5% filled with fat; only 1.5% of the braincase contains brain tissue. The cheeks of the coelacanth are unique because the opercular bone is very small and holds a large soft-tissue opercular flap. A spiracular chamber is present, but the spiracle is closed and never opens during development.[27] Coelacanth also possess a unique rostral organ within the ethmoid region of the braincase.[5][28] Also unique to extant coelacanths is the presence of a "fatty lung" or a fat-filled single-lobed vestigial lung, homologous to other fishes' swim bladder. The parallel development of a fatty organ for buoyancy control suggest a unique specialization for deep-water habitats. There has also been discovered small, hard but flexible plates around the vestigial lung in adult specimen, though not around the fatty organ. The plates most likely had a regulation function for the volume of the lung.[29] Due to the size of the fatty organ, researchers assume it's responsible for the kidney's unusual relocation. The two kidneys, which are fused into one,[30] are located ventrally within the abdominal cavity, posterior to the cloaca.[31]

General description

Latimeria chalumnae
West Indian Ocean coelacanth caught on 21 January 1965, near Mutsamudu (Anjouan, Comoro Islands)
Pectoral fin Latimeria chalumnae
Pectoral fin of a West Indian Ocean coelacanth

Latimeria chalumnae and L. menadoensis are the only two known living coelacanth species.[5][32] The word "coelacanth" is derived from the Greek for “hollow spine”, because of the fish's unique hollow spine fins.[28] Coelacanths are large, plump, lobe-finned fish that can grow to more than 2 meters (6 feet 6 inches) and weigh around 90 kilograms (200 pounds). They are estimated to live for 60 years or more.[33] Modern coelacanths appear larger than those found as fossils.[34]

They are nocturnal piscivorous drift-hunters.[35] The body is covered in cosmoid scales that act as armor.[36] Coelacanths have eight fins – 2 dorsal fins, 2 pectoral fins, 2 pelvic fins, 1 anal fin and 1 caudal fin. The tail is very nearly equally proportioned and is split by a terminal tuft of fin rays that make up its caudal lobe. The eyes of the coelacanth are very large, while the mouth is very small. The eye is acclimatized to seeing in poor light by rods that absorb mostly short wavelengths. Coelacanth vision has evolved to a mainly blue-shifted color capacity.[37] Pseudomaxillary folds surround the mouth and replace the maxilla, a structure absent in coelacanths. Two nostrils, along with four other external openings, appear between the premaxilla and lateral rostral bones. The nasal sacs resemble those of many other fish and do not contain an internal nostril. The coelacanth's rostral organ, contained within the ethmoid region of the braincase, has three unguarded openings into the environment and is used as a part of the coelacanth's laterosensory system.[5] The coelacanth's auditory reception is mediated by its inner ear, which is very similar to that of tetrapods because it is classified as being a basilar papilla.[38]

Coelacanth locomotion is unique. To move around they most commonly take advantage of up- or down-wellings of current and drift. Their paired fins stabilize movement through the water. While on the ocean floor, they do not use the paired fins for any kind of movement. Coelacanths create thrust with their caudal fins for quick starts. Due to the abundance of its fins, the coelacanth has high maneuverability and can orient its body in almost any direction in the water. They have been seen doing headstands as well as swimming belly up. It is thought that the rostral organ helps give the coelacanth electroperception, which aids in movement around obstacles.[35]

DNA

In 2013, a group led by Chris Amemiya and Neil Shubin published the genome sequence of the coelacanth in the journal Nature. The African coelacanth genome was sequenced and assembled using DNA from a Comoros Islands Latimeria chalumnae specimen. It was sequenced by Illumina sequencing technology and assembled using the short read genome assembler ALLPATHS-LG.[39]

Due to their lobed fins and other features, it was once hypothesized that the coelacanth might be the most recent shared ancestor between terrestrial and marine vertebrates.[38][40] But after sequencing the full genome of the coelacanth, it was discovered that the lungfish is the most recent shared ancestor. Coelacanths and lungfish had already diverged from a common ancestor before the lungfish made the transition to land.[41]

The vertebrate land transition is one of the most important steps in our evolutionary history. We conclude that the closest living fish to the tetrapod ancestor is the lungfish, not the coelacanth. However, the coelacanth is critical to our understanding of this transition, as the lungfish have intractable genome sizes (estimated at 50–100Gb).[39]

Another important discovery made from the genome sequencing is that the coelacanths are still evolving today (but at a relatively slow rate). While they were initially thought to be a prehistoric species that remained unchanged over millions of years, the discovery that they are still evolving, albeit slowly, causes some to question whether "living fossil" is an appropriate descriptor.[41]

One reason the coelacanths are evolving so slowly is the lack of evolutionary pressure on these organisms. They have few predators, and live deep in the ocean where conditions are very stable. Without much pressure for these organisms to adapt to survive, the rate at which they have evolved is much slower compared to other organisms.[41]

Taxonomy

Fishapods
In Late Devonian vertebrate speciation, descendants of pelagic lobe-finned fish—like Eusthenopteron—exhibited a sequence of adaptations: Panderichthys, suited to muddy shallows; Tiktaalik with limb-like fins that could take it up onto land; and Early tetrapods in weed-filled swamps, such as Acanthostega which had feet with eight digits and Ichthyostega with limbs. Descendants also included pelagic lobe-finned fish such as the coelacanth species.

The following is a classification of known coelacanth genera and families:[5][10][32][42][43][44][45]

Fossil record

According to genetic analysis of current species, the divergence of coelacanths, lungfish and tetrapods is thought to have occurred about 390 million years ago.[1] Coelacanths were once thought to have undergone extinction 66 million years ago during the Cretaceous–Paleogene extinction event. The first recorded coelacanth fossil, found in Australia, was of a jaw that dated back 360 million years, named Eoachtinistia foreyi. The most recent genus of coelacanth in the fossil record is Megalocoelacanthus, whose disarticulated remains are found in Campanian to possibly earliest Maastrichtian-aged marine strata of the Eastern and Central United States.[46][47] The fossil record is unique because coelacanth fossils were found 100 years before the first live specimen was identified. In 1938, Courtenay-Latimer rediscovered the first live specimen, L. chalumnae, caught off the coast of East London, South Africa. In 1997, a marine biologist on honeymoon discovered the second live species, Latimeria menadoensis, in an Indonesian market.

In July 1998, the first live specimen of Latimeria menadoensis was caught in Indonesia. Approximately 80 species of coelacanth have been described, including the two extant species. Before the discovery of a live specimen, the coelacanth time range was thought to have spanned from the Middle Devonian to the Upper Cretaceous period. Although fossils found during that time were claimed to demonstrate a similar morphology,[4][5] recent studies have expressed the view that coelacanth morphologic conservatism is a belief not based on data.[8][9][10][48]

The following cladogram is based on multiple sources.[10][43][44][45]

Coelacanthiformes
Whiteiidae

Piveteauia

Whiteia

Rebellatricidae

Rebellatrix

Latimerioidei

Garnbergia

Mawsoniidae

Chinlea

Parnaibaia

Mawsonia

Axelrodichthys

Diplurus

Libys

Latimeriidae

Holophagus

Undina

Macropoma

Swenzia

Latimeria

Timeline of genera

Geographic distribution

Latimeria distribution RUS
Geographical distribution of coelacanth.

The current coelacanth range is primarily along the eastern African coast, although Latimeria menadoensis was discovered off Indonesia. Coelacanths have been found in the waters of Kenya, Tanzania, Mozambique, South Africa, Madagascar, Comoros and Indonesia.[4] Most Latimeria chalumnae specimens that have been caught have been captured around the islands of Grande Comore and Anjouan in the Comoros Archipelago (Indian Ocean). Though there are cases of L. chalumnae caught elsewhere, amino acid sequencing has shown no big difference between these exceptions and those found around Comore and Anjouan. Even though these few may be considered strays, there are several reports of coelacanths being caught off of the coast of Madagascar. This leads scientists to believe that the endemic range of Latimeria chalumnae coelacanths stretches along the eastern coast of Africa from the Comoros Islands, past the western coast of Madagascar to the South African coastline.[5] Mitochondrial DNA sequencing of coelacanths caught off the coast of southern Tanzania suggests a divergence of the two populations some 200,000 years ago. This could refute the theory that the Comoros population is the main population while others represent recent offshoots.[49]

The geographical range of the Indonesia coelacanth, Latimeria menadoensis, is believed to be off the coast of Manado Tua Island, Sulawesi, Indonesia in the Celebes Sea.[3] Key components confining coelacanths to these areas are food and temperature restrictions, as well as ecological requirements such as caves and crevices that are well-suited for drift feeding.[50] Teams of researchers using submersibles have recorded live sightings of the fish in the Sulawesi Sea as well as in the waters of Biak in Papua.[51][52]

Ecology

Anjouan Island and the Grande Comore provide ideal underwater cave habitats for coelacanths. The islands' underwater volcanic slopes, steeply eroded and covered in sand, house a system of caves and crevices which allow coelacanths resting places during the daylight hours. These islands support a large benthic fish population that help to sustain coelacanth populations.[50][53]

During the daytime, coelacanths rest in caves anywhere from 100 to 500 meters deep. Others migrate to deeper waters.[4][5] The cooler waters (below 120 meters) reduce the coelacanths' metabolic costs. Drifting toward reefs and night feeding saves vital energy.[50] Resting in caves during the day also saves energy otherwise used to fight currents.[53]

Coelacanth1
Latimeria chalumnae model in the Oxford University Museum of Natural History, showing the coloration in life.

Coelacanths are nocturnal piscivores who feed mainly on benthic fish populations and various cephalopods. They are "passive drift feeders", slowly drifting along currents with only minimal self-propulsion, eating whatever prey they encounter.[50][53]

Coelacanths are fairly peaceful when encountering others of their kind, remaining calm even in a crowded cave. They do avoid body contact, however, withdrawing immediately if contact occurs. When approached by foreign potential predators (e.g. a submersible), they show panic flight reactions, suggesting that coelacanths are most likely prey to large deepwater predators. Shark bite marks have been seen on coelacanths; sharks are common in areas inhabited by coelacanths.[53] Electrophoresis testing of 14 coelacanth enzymes shows little genetic diversity between coelacanth populations. Among the fish that have been caught were about equal numbers of males and females.[5] Population estimates range from 210 individuals per population all the way to 500 per population.[5][54] Because coelacanths have individual color markings, scientists think that they recognize other coelacanths via electric communication.[53]

Life history

Axelrodichthys araripensis 1
Fossil of Axelrodichthys araripensis, an extinct coelacanthiform
Latimeria chalumnae embryo
Latimeria chalumnae embryo with its yolk sac from the Muséum national d'histoire naturelle

Coelacanths are ovoviviparous, meaning that the female retains the fertilized eggs within her body while the embryos develop during a gestation period of over a year. Typically, females are larger than the males; their scales and the skin folds around the cloaca differ. The male coelacanth has no distinct copulatory organs, just a cloaca, which has a urogenital papilla surrounded by erectile caruncles. It is hypothesized that the cloaca everts to serve as a copulatory organ.[5][7]

Coelacanth eggs are large with only a thin layer of membrane to protect them. Embryos hatch within the female and eventually are given live birth, which is a rarity in fish. This was only discovered when the American Museum of Natural History dissected its first coelacanth specimen in 1975 and found it pregnant with five embryos.[55] Young coelacanths resemble the adult, the main differences being an external yolk sac, larger eyes relative to body size and a more pronounced downward slope of the body. The juvenile coelacanth's broad yolk sac hangs below the pelvic fins. The scales and fins of the juvenile are completely matured; however, it does lack odontodes, which it gains during maturation.[7]

A study that assessed the paternity of the embryos inside two Coelacanth females indicated that each clutch was sired by a single male.[56] This could mean that females mate monandrously, i.e. with one male only. Polyandry, female mating with multiple males, is common in both plants and animals and can be advantageous (e.g. insurance against mating with an infertile or incompatible mate), but also confers costs (increased risk of infection, danger of falling prey to predators, increased energy input when searching for new males). Alternatively, the study's results could indicate that, despite female polyandry, one male is used to fertilise all the eggs, potentially through female sperm choice or last-male sperm precedence.

Conservation

Coelacanth sea world
Coelacanth

Because little is known about the coelacanth, the conservation status is difficult to characterize. According to Fricke et al. (1995), there should be some stress put on the importance of conserving this species. From 1988 to 1994, Fricke counted some 60 individuals of L. chalumnae on each dive. In 1995 that number dropped to 40. Even though this could be a result of natural population fluctuation, it also could be a result of overfishing. The IUCN currently classifies L. chalumnae as Critically Endangered,[57] with a total population size of 500 or fewer individuals.[5] L. menadoensis is considered Vulnerable, with a significantly larger population size (fewer than 10,000 individuals).[58]

Currently, the major threat towards the coelacanth is the accidental capture by fishing operations.[59] Coelacanths usually are caught when local fishermen are fishing for oilfish. Fishermen sometimes snag a coelacanth instead of an oilfish because they traditionally fish at night, when oilfish (and coelacanths) feed. Before scientists became interested in coelacanths, they were thrown back into the water if caught. Now that there is an interest in them, fishermen trade them in to scientists or other officials once they have been caught. Before the 1980s, this was a problem for coelacanth populations. In the 1980s, international aid gave fiberglass boats to the local fishermen, which resulted in fishing beyond the coelacanth territories into more fish-productive waters. Since then, most of the motors on the boats have broken down so the local fishermen are now back in the coelacanth territory, putting the species at risk again.[5][60]

Different methods to minimize the number of coelacanths caught include moving fishers away from the shore, using different laxatives and malarial salves to reduce the quantity of oilfish needed, using coelacanth models to simulate live specimens, and increasing awareness of the need to protect the species. In 1987 the Coelacanth Conservation Council advocated the conservation of coelacanths. The CCC has many branches of its agency located in Comoros, South Africa, Canada, the United Kingdom, the U.S., Japan and Germany. The agencies were established to help protect and encourage population growth of coelacanths.[5][61]

A "Deep Release Kit" was developed in 2014 and distributed by private initiative, consisting of a weighted hook assembly that allows a fisherman to return an accidentally caught coelacanth to deep waters where the hook can be detached once it hits the sea floor. Conclusive reports about the effectiveness of this method are still pending.[62]

In 2002, the South African Coelacanth Conservation and Genome Resource Programme was launched to help further the studies and conservation of the coelacanth. This program focuses on biodiversity conservation, evolutionary biology, capacity building, and public understanding. The South African government committed to spending R10 million on the program.[63][64] In 2011, a plan for a Tanga Coelacanth Marine Park was designed to conserve marine biodiversity for marine animals including the coelacanth. The park was designed to reduce habitat destruction and improve prey availability for endangered species.[61]

Human consumption

Coelacanths are considered a poor source of food for humans and likely most other fish-eating animals. Coelacanth flesh has high amounts of oil, urea, wax esters, and other compounds that are difficult to digest and can cause diarrhea. Their scales themselves emit mucus, which combined with the excessive oil their bodies produce, make coelacanths a slimy food.[65] Where the coelacanth is more common, local fishermen avoid it because of its potential to sicken consumers.[66]

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Further reading

  • Smith, J. L. B. (1956). Old Fourlegs: the Story of the Coelacanth. Longmans Green.
  • Fricke, Hans (June 1988). "Coelacanths — The Fish That Time Forgot". National Geographic. Vol. 173 no. 6. pp. 824–838. ISSN 0027-9358. OCLC 643483454.
  • Wade, Nicholas (18 April 2013). "Fish's DNA May Explain How Fins Turned to Feet". The New York Times. pp. A3.
  • Thomson, Keith S. (1991). Living Fossil: the Story of the Coelacanth. W. W. Norton.
  • Sepkoski, Jack (2002). "A compendium of fossil marine animal genera". Bulletins of American Paleontology. 364: 560. Archived from the original on 20 February 2009. Retrieved 2011-05-17.
  • Weinberg, Samantha (1999). A Fish Caught In Time: The Search for the Coelacanth. Fourth Estate.
  • Bruton, Mike (2015). When I Was a Fish: Tales of an Ichthyologist. Jacana Media(Pty)Ltd.

External links

Actinistia

Actinistia is a subclass of mostly fossil lobe-finned fishes. This subclass contains the coelacanths (Order Coelacanthiformes), including the two living species of coelacanths, both of the genus Latimeria: the West Indian Ocean coelacanth and the Indonesian coelacanth.

Chinlea

Chinlea is an extinct genus of Triassic mawsoniid coelacanth fish found in the Southwestern United States states of Arizona and New Mexico. The length of Chinlea was about 1.5 m (5 feet). It weighed around 68 kg. (150 pounds). Chinlea had lobed fins and a slender tail. The teeth were large and sharp.

Gwyneddosaurus

Gwyneddosaurus is an extinct genus of aquatic tanystropheid reptile. The type species, G. erici was described in 1945 by Wilhelm Bock, who identified it as a coelurosaurian dinosaur related to Podokesaurus (at the time, "podokesaurids" were thought to be coelurosaurians). Its remains were found in the Upper Triassic Lockatong Formation of Montgomery County, eastern Pennsylvania, and include skull fragments, several vertebra, ribs, gastralia, partial shoulder and hip bones, and several forelimb and hindlimb elements found in soft shale. The type specimen is ANSP 15072. It was discovered by Bock's four-year-old son. It was not a large animal; the type skeleton was estimated by Bock as 18 centimetres (7.1 in) long, and its thigh bone was only 23 millimeters long (0.91 in).Friedrich von Huene assigned the animal to Protorosauria in 1948 as the smallest known member of the group, finding it to be most like Macrocnemus. Steel (1970) classified it as a theropod dinosaur, whereas Olsen and Baird (1986) identified it as a chimera of mixed remains from a coelacanth and possibly the tanystropheid Tanytrachelos; Olsen and Flynn (1989) later modified this interpretation, describing the type specimen of Gwyneddosaurus as a "gastric ejection" (regurgitation) composed of Tanytrachelos bones and possibly scraps of a coelacanth. They noted that this would make Gwyneddosaurus a senior synonym of Tanytrachelos, and recommended conserving the younger but better-represented genus.

Indonesian coelacanth

The Indonesian coelacanth (Latimeria menadoensis, Indonesian: raja laut) is one of two living species of coelacanth, identifiable by its brown color. It is listed as vulnerable by the IUCN. The other species, L. chalumnae (West Indian Ocean coelacanth) is listed as critically endangered.

J. L. B. Smith

James Leonard Brierley Smith, known always as "J. L. B. Smith", (26 September 1897 – 8 January 1968), was a South African ichthyologist, organic chemist, and university professor. He was the first to identify a taxidermied fish as a coelacanth, at the time thought long extinct.

Latimeria

Latimeria is a rare genus of fish that includes two extant species: West Indian Ocean coelacanth (Latimeria chalumnae) and the Indonesian coelacanth (Latimeria menadoensis). They follow the oldest known living lineage of Sarcopterygii (lobe-finned fish and tetrapods), which means they are more closely related to lungfish, reptiles and mammals than to the common ray-finned fishes.

They are found along the coastlines of the Indian Ocean and Indonesia. Since there are only two species of coelacanth and both are threatened, it is one of the most endangered genus of animals in the world. The West Indian Ocean coelacanth is a critically endangered species.

Lists of prehistoric fish

Prehistoric fish are early fish that are known only from fossil records. They are the earliest known vertebrates, and include the first and extinct fish that lived through the Cambrian to the Quaternary. The study of prehistoric fish is called paleoichthyology. A few living forms, such as the coelacanth are also referred to as prehistoric fish, or even living fossils, due to their current rarity and similarity to extinct forms. Fish which have become recently extinct are not usually referred to as prehistoric fish.

Macropoma

Macropoma (from Greek μακρός "large" + πόμα "cover", after its large operculum) is an extinct genus of coelacanth in the class Sarcopterygii. These fishes have apparently been extinct for over 70 million years and are most closely related to the modern coelacanth Latimeria.

Fossils of Macropoma have been found in both England and Czechoslovakia. Recorded fossils have bodies under two feet in length. A modern coelacanth measures five or more, but in other respects the two genera are remarkably similar, and share the same body plan with a three-lobed tail and stalked fins.Macropoma grew to a length of 22 inches (55 centimeters) and would have preyed upon smaller aquatic species.

Marjorie Courtenay-Latimer

Marjorie Eileen Doris Courtenay-Latimer (24 February 1907 – 17 May 2004) was the South African museum official who in 1938 brought to the attention of the world the existence of the coelacanth, a fish thought to have been extinct for sixty-five million years.

Mawsoniidae

Mawsoniidae is an extinct family of prehistoric coelacanth fishes which lived during the Triassic to Cretaceous period.

Monster on the Campus

Monster on the Campus (a.k.a. Monster in the Night and Stranger on the Campus) is a 1958 American black-and-white science fiction/horror film from Universal-International, produced by Joseph Gershenson, directed by Jack Arnold, from a script by David Duncan, that stars Arthur Franz, Joanna Cook Moore, Nancy Walters, Troy Donohue, and Whit Bissell. The film was theatrically released as a double feature with the British horror film Blood of the Vampire.

The film's storyline tells of a university science professor who accidentally comes into contact with the irradiated blood of a coelacanth, which causes him to "regress" to being a primitive caveman.

Palaeoctopus

Palaeoctopus newboldi is an extinct basal octopod that lived in the Late Cretaceous, approximately 89 to 71 million years ago. Fossil material assigned to this species originates from the Mount Hajoula region in Lebanon. The holotype was found below the Old Covent, Sahel-el-Alma, Mount Lebanon and is deposited at the Natural History Museum in London. It might belong to the Cirrina or be more basal in the Octopoda. Specimens from the Turonian of Vallecino, Mexico, originally described as P. pelagicus, are reinterpreted to be portions of a coelacanth.

Rebellatrix

Rebellatrix divaricerca ("rebel coelacanth (with a) forked tail", after the unique tail fin) is a large prehistoric coelacanth from the Lower Triassic Sulphur Mountain formation and Wapiti Lake Provincial Park of British Columbia. It is the only known species of the family Rebellatricidae. R. divaricerca's most distinguishing feature was its tuna-like forked tail (unusual for an actinistian fish), which suggested a fast-swimming and active lifestyle, unlike coelacanths related to the living species.The holotype specimen is a nearly complete fossil, with the exception of some fins and a large amount of the skull, as well as an incomplete tail fin. Three other specimens reveal the rest of the tail. The rebel coelacanth may have reached 1.30 metres (4 ft 3 in) in length. In addition to its uniquely forked (and symmetrical) tail fin, the posterior dorsal fin is behind the anal fin rather than opposite it. Rebellatrix is believed to have been a fast-swimming predator, since its tail is clearly built for speed, and modern coelacanths only use the tail fin when attacking prey, and would have been one of the first non-sharks to fill this niche.

Retro Game Challenge

Retro Game Challenge, known in Japan as GameCenter CX: Arino no Chōsenjō (ゲームセンターCX 有野の挑戦状, Gēmu Sentā Shī Ekkusu Arino no Chōsenjō, Game Center CX: Arino's Challenge), is a Nintendo DS game developed by indieszero and published by Namco Bandai Games. It is based on the television series GameCenter CX and Shinya Arino gave much input into the game creation process. The game was released on November 15, 2007 in Japan, and in North America from Xseed Games on February 10, 2009. The game received a score of 33/40 from Famitsu. On February 26, 2009, a sequel, GameCenter CX 2, was released in Japan. Xseed Games announced that the game was not likely to be translated into English.

Rhabdoderma

Rhabdoderma is an extinct genus of coelacanth fish in the class Sarcopterygii. It lived in the Carboniferous, and its fossils have been found in Europe and North America.

Sarcopterygii

The Sarcopterygii () or lobe-finned fish (from Greek σάρξ sarx, flesh, and πτέρυξ pteryx, fin)—sometimes considered synonymous with Crossopterygii ("fringe-finned fish", from Greek κροσσός krossos, fringe)—constitute a clade (traditionally a class or subclass) of the bony fish, though a strict cladistic view includes the terrestrial vertebrates.

The living sarcopterygians include two species of coelacanths and six species of lungfish.

Serenichthys

Serenichthys kowiensis is a fossil species of coelacanth described in 2015 from near Grahamstown in South Africa.

Some 30 complete specimens of this new species were found in the black shale lagerstätte on Waterloo Farm, preserved by the mud of an ancient estuary dating back to the Famennian stage of the Late Devonian some 360 million years ago. In an article published in the Zoological Journal of the Linnean Society and jointly authored by paleontologists Michael Coates of the University of Chicago and Robert Gess from the University of the Witwatersrand, the find is described as the earliest coelacanth to be discovered from Africa. Gess first identified coelacanth remains from this locality in the 1990s, but these were poorly preserved and unsuitable for formal description. Subsequent work produced many more specimens, some preserved in fine detail. According to the authors it is the Devonian coelacanth most similar to the hypothetical ancestor of modern coelacanths - its fossil remains lie a mere 100 km from the mouth of the Chalumna River, where Latimeria chalumnae was first found in 1938. In keeping with the use of river names, 'kowiensis' is after the Kowie River which has its headwaters in the hills surrounding the site, while 'Serenichthys' honours Serena Gess, who provided storage space for some 70 tons of fossil-bearing black shale.Coelacanths are thought to have originated in the Devonian, 419.2 ± 3.2 million years ago. Five species of reconstructable coelacanth were previously known from this period, and were found in North America, Europe, China and Australia. At the time these fossils formed in an estuary adjacent to the semi-enclosed Agulhas Sea, Africa was still part of Gondwana, together with India, Australia, Antarctica and South America. All the whole impressions found were of juveniles, suggesting that S. kowiensis was using this shallow estuary as a nursery, behaviour still seen in modern fish. The extant coelacanth, Latimeria, bears live young, but whether these also congregate in nurseries is as yet unknown. This site becomes the earliest known coelacanth nursery, predating Rhabdoderma exiguum in the 300 million-year-old Mazon Creek beds of Illinois.

All specimens of Serenichthys kowiensis have been added to the palaeontological collection of the Albany Museum in Grahamstown.

Specific name (zoology)

In zoological nomenclature, the specific name (also specific epithet or species epithet) is the second part (the second name) within the scientific name of a species (a binomen). The first part of the name of a species is the name of the genus or the generic name. The rules and regulations governing the giving of a new species name are explained in the article species description.

Example

The scientific name for humans is Homo sapiens, which is the species name, consisting of two names: Homo is the "generic name" (the name of the genus) and sapiens is the "specific name".

West Indian Ocean coelacanth

The West Indian Ocean coelacanth (Latimeria chalumnae), sometimes known as gombessa, African coelacanth, or simply coelacanth, is one of two extant species of coelacanth, a rare order of vertebrates more closely related to lungfish, reptiles and mammals than to the common ray-finned fishes. It has a vivid blue pigment, and is the better known of the two extant species. The species has been assessed as critically endangered on the IUCN Red List.

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