Megachasma

Megachasma
Temporal range: Priabonian–recent
Megachasma pelagios
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
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 Oligocene–Miocene 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]

  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." [1]
  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.[2]
  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