Kingdom Animalia
Phylum Chordata
Class Actinopterygii
Subclass Neopterygii
Order Pachycormiformes
Family Pachycormidae
Genus Leedsichthys
1st Species Leedsichthys problematicus
Other attributes
Time Range 167.3-152.1 mya
Location United Kingdom, Germany, Chile, France
Name Meaning Leeds' fish
Physical Dimensions 16.5 meters long
Weight 40 tonnes
Dietary Classification Planktivore

Leedsichthys is a pachycormid pachycormiform ray-finned bony fish from the Middle-Late Jurassic of the United Kingdom, Germany, Chile, and France. It was named in 1889 by Arthur Smith Woodward. It was the largest bony fish to exist, and was originally thought to be 25 meters long; however, scientists now agree that it was 9 meters shorter.


Leedsichthys' build was just as great as its size. It was a large fish with a bulky, torpedo-shaped body, thin, skinny fins, and a mid-sized head with large jaws. Its body would have been covered in scaly skin, with bony plates surrounding a region behind its head.


Leedsichthys was a planktivore, sucking up colonies of plankton drifting through the water. Its large, toothless mouth would have been used to filter plankton from the water.


Like the largest marine organisms to exist, Leedsichthys would have been a filter-feeder, using an array of gill rakers in its throat to filter zooplankton (small, planktonic animals) from the water; it is speculated that it also ate phytoplankton (small, planktonic plant matter). In order to feed, it would make water pass through its gills by quickly swimming forward, causing small animals to flow into its mouth; however, it may have been able to actively pump water through its gills in order to achieve a similar purpose. A Leedsichthys bone with a Metriorhynchus tooth has been found, and was once thought to show that the metriorhynchid preyed on the pachycormid; however, the bone didn't heal, and so, it is now assumed that the marine crocodylomorph had scavenged the fish's carcass. Despite this, Leedsichthys wasn't entirely safe from predators when alive, as more advanced thalattosuchians like Dakosaurus would have been able to prey on mid-sized individuals, while pliosaurids like Liopleurodon and Pliosaurus would have been able to pose as a threat to larger ones.

In popular cultureEdit

Leedsichthys was featured in the 3rd episode of the 2003 documentary Chased by Sea Monsters, where it is shown as a large fish that travels in small schools; as well as this, it was oversized to a length of 28 meters. Soon, a weak and dying individual is attacked by a Metriorhynchus and a Hybodus; after the two smaller animals leave, a Liopleurodon (also oversized) comes to eat the giant fish.

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