Leedsichthys problematicus

Last updated: May 27, 2024
Verified by: AZ Animals Staff
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Leedsichthys is one of the largest fish ever discovered


Leedsichthys Scientific Classification

Scientific Name
Leedsichthys problematicus

Read our Complete Guide to Classification of Animals.

Leedsichthys Conservation Status

Leedsichthys Locations

Leedsichthys Locations

Leedsichthys Facts

Main Prey
Fun Fact
Leedsichthys is one of the largest fish ever discovered
Biggest Threat
decline in the plankton population
Most Distinctive Feature
largest fish ever discovered
Distinctive Feature
ray fin, size
Liopleurodon and Metriorhynchus
Favorite Food
Number Of Species
England, France, Germany and Chile

Leedsichthys Physical Characteristics

99208 lb (45 metric tons)
10m - 25m (32.8ft - 82.0ft)

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Leedsichthys is a genus of gigantic prehistoric fish that lived from the middle to late Jurrasic period. This ray-finned fish was one of the largest in its family and one of the largest fish ever discovered. Although dozens of fossils from this fish genus have been found so far, scientists still have difficulty getting a clear picture of this fish’s size and appearance due to the incomplete nature of the fossils discovered so far.

Description & Size

The genus Leedsichthys was named after Sir Alfred Nicholson Leeds, the paleontologist who discovered this genus’s first fossil. The first and only species of this genus is Leedsichthys problematicus. The species name refers to the difficulty that scientists have experienced in reconstructing this giant fish

The controversy in the species size is the partial and fragmented nature of the fossils that paleontologists have dug up so far. Some parts of the fish’s bone, notably the front of the skull and some parts of the vertebral bones, are cartilaginous, which means there’s no way they would have been preserved in the fossil record. 

The Leedsichthys is undoubtedly one of the largest bony fishes ever discovered. Due to the fragmented nature of the remains recovered so far, the exact size of this fish is still a subject of open debate and speculation. Most experts agree on a length of at least ten meters for this fish. However, some remains appear to be larger than this estimate. Because of this, many scientists have pushed their maximum estimate to about 16 meters. More generous estimates put the Leedsichthys’ maximum length at over 25 meters. 

The Leedsichthys had a relatively large and elongated head. It might have had a snout, but this is not recorded in the fossils discovered so far. From the fossils of this ancient fish, it is clear that it had bony fin rays. Leedsichthys had two pectoral fins on the lower side of the body. These were large and elongated with a slight curve to the side. They also had a dorsal fin and a triangular anal fin, but a pelvic fin was absent. 

3-D Rendered Illustration of Leedsichthys in Water

Leedsichthys lived in the middle to late Jurassic Period and fed on plankton.


Diet – What Did Leedsichthys Eat?

The mouth of this Jurassic fish was equipped with as many as 40,000 teeth. Yet, despite its massive size and fearsome dentition, this giant fish did not prey on big fishes or marine reptiles. Instead, it was a filter-feeder whose feeding habit is more similar to the present-day blue whale. The Leedsichthys fed predominantly on planktons that were abundant in the Jurassic waters where they lived. This fish could swallow hundreds of gallons of water in a single gulp and filter it with giant mesh-like plates at the back of its mouth. 

Habitat – When and Where It Lived

Scientists have found fossil remains of Leedsichthys across various locations. These include England, Northern Germany, Chile, and France. Fragmented fossils have also been found in Argentina. 

Threats And Predators

The seas of the Jurassic period where the Leedsichthys was found were a dangerous and unforgiving ecosystem. It didn’t help that this giant fish had no form of defense against predators like the Liopleurodon and Metriorhynchus, which were quite abundant at the time. Although a single attack was probably not enough to take out a full-grown Leedsichthys, an attack by a group of predators would have been enough to inflict fatal damage. 

Discoveries and Fossils – Where Leedsichthys was Found

Fossils of this prehistoric giant were discovered during an interesting period in the field of Paleontology. This period in the 19th century was characterized by ongoing competition between various notable paleontologists. Amateur paleontologist Alfred Nicholson Leeds was the first to discover the bones of this giant pit in a loam pit near Peterborough, England. This was in 1886. However, the bones were initially misidentified as belonging to a stegosaurus dinosaur. 

The following year, renowned Paleontologist Othniel Marsh correctly identified the remains as that of a prehistoric fish. Subsequently, Leeds excavated even more fossils and sold them to museums. 

Extinction – When Did It Die Out?

Leedsichthys is one of several massive-sized filter feeders that swam in the seas of the Mesozoic era for more than 100 million years. This fish lived between the Middle Jurassic till the end of the Cretaceous period. The sea at the time had a massive population of planktons, which allowed large fishes like the Leedsichthys to develop. However, this giant filter-feeder most likely went extinct when the plankton populations began to plunge mysteriously during the Cretaceous period.

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Leedsichthys FAQs (Frequently Asked Questions) 

Why did Leedsichthys go extinct?

Leedsichthys lived during the Jurassic period. During this time, there was a boom in the plankton population. However, the krill population plunged mysteriously at the start of the Cretaceous period, leading to the decline of this giant filter.

Was the Leedsichthys a predator?

Leedsichthys was a giant fish whose size would have dwarfed that of any other sea animal that lived around the same time. However, this tiny shrimp was not a predator. Instead, it fed on planktons. Leedsichthys was a filter-feeder. The fish would take a large mouthful of plankton-rich water and sliver them through giant mesh plates at the back of its mouth. This feeding habit is similar to that of the modern blue whale.

Is Megalodon bigger than Leedsichthys?

Yes. Average estimates put the Leedsichthys at an approximate length of 16.5m. This was significantly higher than the length of the average Megalodon. However, unlike the prehistoric shark, Leedsichthys was not a predator.

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