Leedsichthys
Encyclopedia
Leedsichthys was a giant pachycormid (an extinct group of Mesozoic
bony fish) that lived in the oceans of the Middle Jurassic period. The closest living relative of the pachycormids is the bowfin
, Amia calva, but this is only very distantly related.
of England
, northern Germany
, the Oxfordian
of Chile
, and the Kimmeridgian
of France.
, who described the specimen
in 1889, estimated it to be 30 feet (around 9 metres) long, by comparing the tail of Leedsichthys with another pachycormid, Hypsocormus
. In 1986, Martill compared the bones of Leedsichthys to a pachycormid that he had recently discovered, but the unusual proportions of that specimen gave a wide range of possible sizes. More recent estimates, from documentation of historical finds and the excavation of the most complete specimen ever from the Star Pit near Whittlesey
, Peterborough
, support Smith Woodward's figures of between 30 and 33 feet (9 and 10 meters). Recent work on growth ring structures within the remains of Leedsichthys have also indicated that it would have taken 21–25 years to reach these lengths, and isolated elements from other specimens indicate that a maximum size of just over 16 metres (53 feet ) is not unreasonable.
Like the largest fish today, the whale sharks and basking sharks, Leedsichthys problematicus derived its nutrition using an array of specialised gill raker
s lining its gill basket to extract zooplankton
from the water passing through its mouth and across its gills. There is little direct evidence for predation as opposed to scavenging on Leedsichthys remains, but specimen P.6924 in the Natural History Museum
of London
shows signs of bites from a Liopleurodon
-sized pliosaur
. These bites have then healed, indicating that Leedsichthys could even escape the top predator of the Oxford Clay
seas, probably as a result of its powerful tail.
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
bony fish) that lived in the oceans of the Middle Jurassic period. The closest living relative of the pachycormids is the bowfin
Bowfin
The Bowfin, Amia calva, is the last surviving member of the order Amiiformes , and of the family Amiidae...
, Amia calva, but this is only very distantly related.
Discovery and assignment of name
The name Leedsichthys means "Leeds' fish", after the fossil collector Alfred Nicholson Leeds, who discovered it before 1886 near Peterborough, England. The fossils found by Leeds gave the fish the specific epithet problematicus, because the remains were so fragmented that they were extremely hard to recognize and interpret.Fossil range
The fossil remains of Leedsichthys have been found in the CallovianCallovian
In the geologic timescale, the Callovian is an age or stage in the Middle Jurassic, lasting between 164.7 ± 4.0 Ma and 161.2 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the Oxfordian....
of England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, northern Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, the Oxfordian
Oxfordian stage
The Oxfordian is, in the ICS' geologic timescale, the earliest age of the Late Jurassic epoch, or the lowest stage of the Upper Jurassic series. It spans the time between 161.2 ± 4 Ma and 155.7 ± 4 Ma...
of Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
, and the Kimmeridgian
Kimmeridgian
In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....
of France.
Size
Although the remains of over seventy individuals have been found, most of them are partial and fragmentary, which has made it difficult to estimate the fish's length. Arthur Smith WoodwardArthur Smith Woodward
Sir Arthur Smith Woodward was an English palaeontologist.-Biography:Woodward was born in Macclesfield, Cheshire, England and was educated there and at Owens College, Manchester. He joined the staff of the Department of Geology at the Natural History Museum in 1882. He became assistant Keeper of...
, who described the specimen
Specimen
A specimen is a portion/quantity of material for use in testing, examination, or study.BiologyA laboratory specimen is an individual animal, part of an animal, a plant, part of a plant, or a microorganism, used as a representative to study the properties of the whole population of that species or...
in 1889, estimated it to be 30 feet (around 9 metres) long, by comparing the tail of Leedsichthys with another pachycormid, Hypsocormus
Hypsocormus
Hypsocormus is an extinct genus of teleost fish from the Jurassic period of Europe.Hypsocormus was a fast-swimming predatory fish about long, with a half moon-shaped caudal fin similar to that of a modern mackerel. It had a single dorsal fin, elongated pectoral fins and tiny pelvic fins about half...
. In 1986, Martill compared the bones of Leedsichthys to a pachycormid that he had recently discovered, but the unusual proportions of that specimen gave a wide range of possible sizes. More recent estimates, from documentation of historical finds and the excavation of the most complete specimen ever from the Star Pit near Whittlesey
Whittlesey
Whittlesey, historically known as Whittlesea as the name of the railway station is still spelt, or Witesie, is an ancient Fenland market town around six miles east of Peterborough in the county of Cambridgeshire in England...
, Peterborough
Peterborough
Peterborough is a cathedral city and unitary authority area in the East of England, with an estimated population of in June 2007. For ceremonial purposes it is in the county of Cambridgeshire. Situated north of London, the city stands on the River Nene which flows into the North Sea...
, support Smith Woodward's figures of between 30 and 33 feet (9 and 10 meters). Recent work on growth ring structures within the remains of Leedsichthys have also indicated that it would have taken 21–25 years to reach these lengths, and isolated elements from other specimens indicate that a maximum size of just over 16 metres (53 feet ) is not unreasonable.
Like the largest fish today, the whale sharks and basking sharks, Leedsichthys problematicus derived its nutrition using an array of specialised gill raker
Gill raker
Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch and are involved with filter feeding tiny prey. They are not to be confused with the gill filaments that compose the bony part of the gill. Rakers are usually present in two rows, projecting from both the...
s lining its gill basket to extract zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
from the water passing through its mouth and across its gills. There is little direct evidence for predation as opposed to scavenging on Leedsichthys remains, but specimen P.6924 in the Natural History Museum
Natural History Museum
The Natural History Museum is one of three large museums on Exhibition Road, South Kensington, London, England . Its main frontage is on Cromwell Road...
of London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
shows signs of bites from a Liopleurodon
Liopleurodon
Liopleurodon is a genus of large, carnivorous marine reptile belonging to the Pliosauroidea, a clade of short-necked plesiosaurs. Two species of Liopleurodon lived during the Callovian stage of the Middle Jurassic Period , while the third, L. rossicus, lived during the Late Jurassic...
-sized pliosaur
Pliosaur
Pliosauroidea is an extinct clade of marine reptiles. Pliosauroids, also commonly known as pliosaurs, are known from the Jurassic and Cretaceous Periods. The pliosauroids were short-necked plesiosaurs with large heads and massive toothed jaws. These swimming reptiles were not dinosaurs but distant...
. These bites have then healed, indicating that Leedsichthys could even escape the top predator of the Oxford Clay
Oxford Clay
The Oxford Clay Formation is a Jurassic marine sedimentary rock formation underlying much of southeast England, from as far west as Dorset and as far north as Yorkshire. The Oxford Clay is of middle Callovian to lower Oxfordian age and comprises 2 main facies. The lower facies comprises the...
seas, probably as a result of its powerful tail.
External links
- For more on the Star Pit dig of 2002-2003 look here and also here where the dig was featured in the BBC-Open University series Fossil Detectives.
- For a more accurate reconstruction of Leedsichthys visit Paleocreations. The artist went on to produce the most accurate reconstruction of Leedsichthys to date, which was used on 'Fossil Detectives' (see above).
- The profile of Leedsichthys problematicus from the BBC series Sea Monsters
- "Biggest Fish Ever Found" Unearthed in U.K. National Geographic News. Published October 1, 2003.
- An article on the latest discovery of a Leedsichthys problematicus fossil, estimated 22 meters = 72 feet (21.9 m) long]
- A picture of Leedsichthys problematicus
- An article on Leedsichthys from Darren Nash
- An article on Leedsichthys from BBC news
