Orthacanthus Shark

Orthacanthus is a genus of prehistoric freshwater shark. It was also an member of a group of ancient sharks called xenacanths, all of which were freshwater sharks with long fins down their backs and a spine at the start of the fin. Orthacanthus were the largest of the known xenacanths.

About 260 million years ago, Orthacanthus was the apex predator of freshwater swamps and bayous in Europe and North America. It owned a peculiar set of double-fanged teeth. They first appeared about 400 million years ago in the Devonian, and became extinct just before the Mesozoic period, about 225 million years ago.

The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian, 419.2 million years ago (Mya), to the beginning of the Carboniferous, 358.9 Mya. It is named after Devon, England, where rocks from this period were first studied.

The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established.

Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the "Age of Fishes." The first ray-finned and lobe-finned bony fish appeared, while the placoderms began dominating almost every known aquatic environment. The ancestors of all four-limbed vertebrates (tetrapods) began adapting to walking on land, as their strong pectoral and pelvic fins gradually evolved into legs. In the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician.

The first ammonites, species of molluscs, appeared. Trilobites, the mollusc-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction which started about 375 million years ago severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida.

The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, and the early formation of the small continent of Euramerica in between.

The sediments in West Cumbria represent a coastal environment and amongst the carbonised remains of ancient plants, occasionally the distinctive tricuspid (three pointed) teeth of the Orthacanthus can sometimes be found from the Devonion period.
  • In 2009, an Orthacanthus Tooth from Bolsovian shale was found by K & C Paxton, on the Whitehaven shore.
Orthacanthus Prehistoric Shark

The body of the Orthacanthus reached nearly 10 feet (3 meters) in length, and weighed 100lbs (45kg). The shark possessed a peculiar set of double-fanged teeth. They first appeared about 400 million years ago in the Devonian, and became extinct just before the Mesozoic, about 225 million years ago.

Orthacanthus would have specialised in larger and more powerful prey that it would have seized with its double fanged teeth.‭ ‬The overall eel like body morph of Orthacanthus is a reflection of its habitat.‭ ‬Rather than being a pelagic open seas predator,‭ ‬Orthacanthus hunted in freshwater swamps and waterways that would have been densely overgrown in areas.‭

By having a long body with short fins Orthacanthus could navigate these waters without getting stuck in submerged debris and vegetation.‭ ‬It's possible that Orthacanthus may have used ambush tactics like lurking within the submerged debris‭ ‬and plants waiting for prey to pass by.

The spike that rises up from the back of the head of Orthacanthus seems to have been a defensive feature to stop other predators from clamping their jaws onto its head.‭ ‬These exact predators may still be unknown to science but they may have been other fish like Hyneria,‭ ‬or large amphibian tetrapods.

When alive Orthacanthus likely was an opportunistic predator and probably hunted the many kinds of other fish as well as amphibians it shared its shallow freshwater environment with.  It may also have periodically encountered the giant mammal-like reptile, Dimetrodon, which could have preyed upon it.

A tricuspid Orthacanthus tooth from Bolsovian shale at Whitehaven. Found by K & C Paxton
Orthacanthus Tooth Found At Whitehaven


Whitehaven had been small harbour and fishing village from 13th century or earlier. Expansion began in mid-17th century with building of piers by Lowthers 1632-4 and 1679-81 and granting of market charter 1660. By the 1680s it had grown rapidly, expanding from village of c.30 households in early 17th century to a town of over 1,000 inhabitants by 1685, which more than doubled to 2,281 by 1696. Sir John Lowther had laid out grid of streets by 1680s, making Whitehaven the earliest planned new town in post-medieval Britain.

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