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Life restoration of two Leedsichthys

Leedsichthys ("Leeds' fish") was a giant bony fish of the Middle Jurassic Period. Fossils of the genus are known from both Europe and South America.


Many specimens of Leedsichthys exist, but they are all fragmentary. As such, it is difficult to determine its exact appearance. Its head was most likely large and wide, and its jaws were toothless. Instead, it possessed large gill rakers with which it could filter food such as plankton.[1]


Arthur Smith Woodward, who described the genus, estimated the length of Leedsichthys at nine meters by comparing the proportions of its tail with that of related fishes. His estimate remained unchallenged until 1986, when David Martill compared Leedsichthys to Asthenocormus, another related species.[2] The unusual proportions of that specimen gave a wide range of possible sizes, anywhere from 13 to 27 meters. Martill considered the highest estimates to be plausible sizes for some of the largest examples of Leedsichthys.[3] Subsequently, depictions of Leedsichthys measuring thirty or even thirty-five meters in length became common.[4]

Jeff Liston later concluded by examining both old and new specimens of Leedsichthys that Woodward's original estimates were much more reasonable.[5] A new study in 2013 indicated that the natural size range of Leedsichthys was from ten to seventeen meters, and that it did not grow any larger.[6]


A twelve-meter-long Leedsichthys, compared with a modern diver

Leedsichthys was originally considered to be a type of sturgeon, but it was later placed in the pachycormid family. All pachycormids are now extinct, and their relations with other fish are unclear. They are sometimes considered to be basal teleosts.[7]


In the 1880s, British farmer Alfred Leeds discovered large fish remains from loam pits near Peterborough, England. The scientist John Whitaker Hulke inspected the remains, and initially considered them as the back plates of a stegosaurian dinosaur. In 1888, the famous American paleontologist Othniel Charles Marsh visited Leeds' farm and correctly interpreted the bones as those of a giant fish. The British paleontologist and fish expert Arthur Smith Woodward examined the remains and published a paper in 1889, describing the animal as Leedsichthys problematicus.[8] The specific epithet "problematicus" referred to the poor and fragmentary condition of the fossils. After Woodward published a second description a year later, objections were raised over the name of the animal, which attached a non-Latinized British family name to a Classical Greek word (which was perceived as "barbaric"). As a result, Woodward renamed the animal Leedsia.[9] Under the rules of modern zoological nomenclature, Leedisa is a junior synonym, and subsequently the older name Leedsichthys takes priority and remains in use.

In 2001, a specimen of Leedsichthys was discovered by students at the Star Pit, not far away from the original discovery site of the genus. It was nicknamed "Ariston" after a 1991 commercial for the Indesit Ariston washing machine, which claimed that the machine "went on and on and on". In a similar fashion, the bones of the Leedsichthys specimen seemed to endlessly continue into the face of the excavation pit.[10] The bones were excavated by a team led by Jeff Liston, who went on to write a series of articles and papers about the genus.[11] The specimen was given considerable attention by both the scientific community and the media.



Leedsichthys was a filter feeder, eating plankton and small animals by filtering the ocean water with its mouth and gills.


In 1986, David Martill observed a tooth embedded in a Leedsichthys bone, apparently belonging to the marine crocodilian Metriorhynchus.[12] Jeff Liston later concluded that the bone had not healed, and that this appeared to be evidence of scavenging.

In popular culture[]

The 2001 discovery of "Aniston" and subsequent coverage made Leedsichthys fairly well known. It appeared in the 2003 three-part BBC documentary Sea Monsters, where it is shown traveling in shoals and being preyed upon by groups of Liopleurodon.


  1. Liston, JJ (2008a). Leedsichthys des Vaches Noires ... au peigne fin (translation by M-C Buchy) L’Écho des Falaises (=Ech.des Fal.) No.12: 41-49, 2008 ISSN 1253-6946.
  2. Martill, DM (1986). The world's largest fish. Geology Today March–April: 61-63.
  3. Martill, D.M., 1988, "Leedsichthys problematicus, a giant filter-feeding teleost from the Jurassic of England and France", Neues Jahrbuch fur Geologie und Palaontologie Monatshefte 1988 (11): 670-680
  4. [Ed.] "Catch the 100ft fish", The Mirror, London, England, September 18, 2003
  5. Liston, JJ (2006). From Glasgow to the Star Pit and Stuttgart: A short journey around the world's longest fish. The Glasgow Naturalist 24: 59-71.
  6. Liston, J., Newbrey, M., Challands, T., and Adams, C., 2013, "Growth, age and size of the Jurassic pachycormid Leedsichthys problematicus (Osteichthyes: Actinopterygii) in: Arratia, G., Schultze, H. and Wilson, M. (eds.) Mesozoic Fishes 5 – Global Diversity and Evolution. Verlag Dr. Friedrich Pfeil, München, Germany, pp. 145-175
  7. Arratia, G., 1999, "The monophyly of Teleostei and stem-group teleosts. Consensus and disagreements". –In: Arratia, G. & Schultze, H.-P. (eds.): Mesozoic Fishes 2 – Systematics and Fossil Record: 265-334, München, Dr. Friedrich Pfeil Verlag
  8. Woodward, Smith, A (1889). Preliminary notes on some new and little-known British Jurassic fishes. Geological Magazine Decade 3 Volume 6: 448-455.
  9. Woodward, A.S., 1890, "Note on the gill-rakers of Leedsia problematica – a gigantic fish from the Oxford Clay", Geological Magazine December III(7): 292-293
  10. Douglas Palmer & Hermione Cockburn, 2012, The Fossil Detectives: Discovering Prehistoric Britain, Google eBook, p. 146
  11. Liston, J.J., 2007, A Fish Fit For Ozymandias?: The Ecology, Growth and Osteology of Leedsichthys (Pachycormidae, Actinopterygii), Unpublished PhD Thesis. 464 pp. Faculty of BioMedical & LifeSciences, University of Glasgow, Scotland
  12. Martill, D.M., 1986, "The diet of Metriorhynchus, a Mesozoic marine crocodile", Neues Jahrbuch fur Geologie und Paläontologie, Monatshefte 1986: 621-625