Leedsichthys

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. 

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.

Similar Animals:

• Blue Whale
• Great White Shark
• Bottlenose dolphin

1. DKFindOut, Available here: https://www.dkfindout.com/us/dinosaurs-and-prehistoric-life/prehistoric-fish/what-was-largest-fish/
2. National Geographic / Riley Black, Available here: https://www.nationalgeographic.com/science/article/130827-paleontology-leedsichthys-problematicus-fish-oceans-science
3. BBC Fact Files, Available here: https://www.bbc.co.uk/science/seamonsters/factfiles/leedsichthys.shtml
4. Wikipedia, Available here: https://en.wikipedia.org/wiki/Leedsichthys
5. Thought Co. / Bob Strauss, Available here: https://www.thoughtco.com/history-of-leedsichthys-1093679