Megachasma

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Megachasma
Temporal range: Priabonian–recent
Megachasma pelagios.jpg
Megachasma pelagios
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Lamniformes
Family: Megachasmidae
Taylor, Compagno & Struhsaker, 1983
Genus: Megachasma
Taylor, Compagno & Struhsaker, 1983
Species

Megachasma is a genus of mackerel sharks. It is usually considered to be the sole genus in the distinct family Megachasmidae, though suggestion has been made that it may belong in the family Cetorhinidae, of which the basking shark is currently the sole extant member. [1] Megachasma is known from a single living species, Megachasma pelagios . [2] [3]

In addition to the living M. pelagios, however, two extinct megamouth species – the Priabonian M. alisonae [4] and the OligoceneMiocene M. applegatei – have also recently been proposed on the basis of fossilized tooth remains. [5] [6] An early ancestor of the recent species Megachasma pelagios was reported from the early Miocene (Burdigalian) of Belgium. [7] However, the Cretaceous-aged M. comanchensis has been recently reclassified as an odontaspid shark in the genus Pseudomegachasma , and is in fact unrelated to the megamouth shark despite similar teeth morphology. [8]

They are a very rare genus of shark that are mainly found in temperate and tropical waters among the Pacific, Atlantic and Indian oceans. The top sighting spots are Taiwan, Japan, and the Philippines. [9]

Related Research Articles

<span class="mw-page-title-main">Megamouth shark</span> Species of shark

The megamouth shark is a species of deepwater shark. Rarely seen by humans, it measures around 5.2 m (17 ft) long and is the smallest of the three extant filter-feeding sharks alongside the relatively larger whale shark and basking shark. Since its discovery in 1976, fewer than 100 specimens have been observed or caught. Like the other two planktivorous sharks, it swims with its mouth wide open, filtering water for plankton and jellyfish. It is recognizable from its large head with rubbery lips. The megamouth is so unlike any other type of shark that it is usually considered to be the sole extant species in the family Megachasmidae, though some scientists have suggested it may belong in the family Cetorhinidae.

<span class="mw-page-title-main">Lamniformes</span> Order of sharks

The Lamniformes are an order of sharks commonly known as mackerel sharks. It includes some of the most familiar species of sharks, such as the great white, as well as more unusual representatives, such as the goblin shark and megamouth shark.

<i>Carcharodon</i> Genus of sharks

Carcharodon is a genus of sharks within the family Lamnidae, colloquially called the "white sharks." The only extant member is the great white shark. The extant species was preceded by a number of fossil (extinct) species including C. hubbelli and C. hastalis. The first appearance of the genus may have been as early as the Early Miocene or Late Oligocene.

<span class="mw-page-title-main">Megalodon</span> Extinct giant shark species from 23 to 3.6 million years ago

Otodus megalodon, commonly known as megalodon, is an extinct species of giant mackerel shark that lived approximately 23 to 3.6 million years ago (Mya), from the Early Miocene to the Pliocene epochs. O. megalodon was formerly thought to be a member of the family Lamnidae and a close relative of the great white shark, but has been reclassified into the extinct family Otodontidae, which diverged from the great white shark during the Early Cretaceous.

<i>Cretoxyrhina</i> Extinct genus of shark

Cretoxyrhina is an extinct genus of large mackerel shark that lived about 107 to 73 million years ago during the late Albian to late Campanian of the Late Cretaceous. The type species, C. mantelli, is more commonly referred to as the Ginsu shark, first popularized in reference to the Ginsu knife, as its theoretical feeding mechanism is often compared with the "slicing and dicing" when one uses the knife. Cretoxyrhina is traditionally classified as the likely sole member of the family Cretoxyrhinidae but other taxonomic placements have been proposed, such as within the Alopiidae and Lamnidae.

This list of fossil fishes described in 2014 is a list of new taxa of placoderms, fossil cartilaginous fishes and bony fishess of every kind that have been described during the year 2014, as well as other significant discoveries and events related to paleontology of fishes that occurred in the year 2014. The list only includes taxa at the level of genus or species.

The Yaquina Formation is a geologic formation in Oregon. It preserves fossils dating back to the Paleogene period.

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This list of fossil fishes described in 2016 is a list of new taxa of jawless vertebrates, placoderms, acanthodians, fossil cartilaginous fishes, bony fishes and other fishes of every kind that have been described during the year 2016, as well as other significant discoveries and events related to paleontology of fishes that occurred in the year 2016. The list only includes taxa at the level of genus or species.

Pseudomegachasma is an extinct genus of filter-feeding shark that was closely related to the modern sand tiger shark. It is known from Cretaceous strata in Russia and the United States, and is the only known planktivorous odontaspid, as well as the oldest known planktivorous elasmobranch. It most likely derived from its closest relative, the piscivorous shark Johnlongia. As its name suggests, it was originally classified under Megachasma, before it was found to be an odontaspid.

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Megachasma applegatei is an extinct species of megamouth shark from the Oligocene to early Miocene of the Western United States. The type fossil was discovered in the San Joaquin Valley in 1973, but only described in 2014, when the species was named after its discoverer, Shelton Applegate.

Megachasma alisonae is an extinct species of megamouth shark that lived during the Eocene. It is the oldest fossil record of a megamouth shark. The type fossil was recovered from the Søvind Marl Formation in Denmark and consists of a single tooth. Based on comparison with the teeth of the recent megamouth species, the length of the animal has been estimated at 1.3–3.5 m (4.3–11.5 ft).

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<i>Cretodus</i> Extinct genus of sharks

Cretodus is an extinct genus of large mackerel sharks belonging to the proposed family Pseudoscapanorhynchidae. Cretodus lived during the Late Cretaceous, ranging from the Cenomanian to the Coniacian. The genus is well-known from strata deposited in the Western Interior Seaway, and from the Late Cretaceous of Europe, Africa, and possibly Asia. Cretodus is primarily represented in the fossil record by isolated teeth and vertebral centra, though a couple of associated dentitions and vertebral columns have been found.

<i>Archaeolamna</i> Extinct genus of sharks

Archaeolamna is an extinct genus of mackerel sharks that lived during the Cretaceous. It contains three valid species which have been found in Europe, North America, and Australia. While it is mostly known from isolated teeth, an associated set of teeth, jaws, cranial fragments, and vertebrae of A. kopingensis is known from the Pierre Shale of Kansas. Teeth of A. k. judithensis were found with a plesiosaur skeleton with bite marks from the Judith River Formation of Montana. It was a medium-sized shark with an estimated total body length of 3–4 metres (9.8–13.1 ft).

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References

  1. Martin, A. P.; Naylor, G. J. (1997). "Independent origins of filter-feeding in megamouth and basking sharks (order Lamniformes) inferred from phylogenetic analysis of cytochrome b gene sequences". In Kazunari Y ano; Jobn F. Morrissey; Yoshitaka Yabumoto; Kazuhiro Nakaya (eds.). Biology of the Megamouth Shark (PDF). Tokyo: Tokai University Press. pp. 39–50.
  2. "Megachasma pelagios Taylor, Compagno & Struhsaker, 1983 Megamouth shark". Fishbase.
  3. "Megachasma pelagios". Florida museum.
  4. Shimada, Kenshu, and David J. Ward. "The oldest fossil record of the megamouth shark from the late Eocene of Denmark, and comments on the enigmatic megachasmid origin."
  5. Shimada, K. 2007. Mesozoic origin for megamouth shark (Lamniformes: Megachasmidae). Journal of Vertebrate Paleontology 27:512–516. (Link at BioOne)
  6. Shimada, K., Welton, B.J., and Long, D.J. 2014. A new fossil megamouth shark (Lamniformes, Megachasmidae) from the Oligocene-Miocene of the western United States. Journal of Vertebrate Paleontology 34:281-290.
  7. De Schutter, P., Everaert, S. 2020. A megamouth shark (Lamniformes: Megachasmidae) in the Burdigalian of Belgium.Geologica Belgica Volume 23 number 3-4 - The Neogene stratigraphy of northern Belgium.
  8. Shimada, Kenshu; Popov, Evgeny V.; Siversson, Mikael; Welton, Bruce J.; Long, Douglas J. (2015-09-03). "A new clade of putative plankton-feeding sharks from the Upper Cretaceous of Russia and the United States". Journal of Vertebrate Paleontology. 35 (5): e981335. Bibcode:2015JVPal..35E1335S. doi:10.1080/02724634.2015.981335. ISSN   0272-4634. S2CID   83793715.
  9. Watanabe, YY, Papastamatiou, YP. Distribution, body size and biology of the megamouth shark Megachasma pelagios. J Fish Biol. 2019; 95: 992– 998. https://doi-org.edu/10.1111/jfb.14007