The Devonian Period is often referred to as the age of fish because it was during this period that the variety of fish began to increase.
However, the actual evolution of fishes began significantly earlier and can be traced all the way back to the Cambrian explosion, roughly 530 years ago.
The evolution of fish species during the Devonian produced some really extraordinary results characterized by the emergence of creatures bigger in size and remarkably different from their present-day ancestors.
Interestingly, a few of these prehistoric creatures are still around, living in the world’s oceans as living fossils.
In this article, we’ll explore 15 of these remarkable prehistoric fish species to better understand the diversity of the ancient aquatic world.
15. Rhizodus
| Name | Rhizodus |
| Name Meaning | Root Tooth |
| Pronunciation | RYE-zoh-duhs |
| Era | Paleozoic – Carboniferous |
| Classification | Rhizodontida, Rhizodontiformes, & Rhizodontidae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 3–5 meters (10-18 feet) |
| Weight | 1 ton (2,200 lbs) |
| Location | Europe and North America |
Rhizodus was a lobe-finned fish about the same size as modern orcas.
It was an apex predator of freshwater lakes, swamps, and river systems and is typically regarded as the largest freshwater fish ever discovered.
Rhizodus is also the only truly massive lobe-finned predator ever found, growing to lengths of about five meters (18 feet).
It was a generalist predator that fed on small to medium-sized fish and amphibians in the carboniferous seas.
There are also speculations that this incredible fish could launch out of the water to catch prey on the shore like crocodiles.
This ancient fish had an impressive dentition that included 22 centimeters (8.7 inches) long fangs in its front jaws.
Rhizodus fossils have been found across various locations in Europe and North America.
14. Megapiranha
| Name | Megapiranha |
| Name Meaning | Large Piranha |
| Pronunciation | MEG-uh-py-RAN-ha |
| Era | Cenozoic – Neogene |
| Classification | Actinopterygii, Characiformes, & Serrasalmidae |
| Diet | Omnivorous |
| Height | N/A |
| Length | 0.7–1.2 meters (2.3–4 feet) |
| Weight | 10 kg (22 lbs) |
| Location | Argentina (South America) |
What if piranhas could grow to twice their current size but were just as ferocious?
What you’ll get is the Megapiranha, an ancient fish that grew to an average length of about 71 centimeters (28 inches) and may have weighed up to 10 kilograms (22 pounds) on average.
Its sharp, serrated teeth were arranged in a single zigzag pattern across its front jaw.
It was alive between eight and ten million years ago in the Miocene Epoch.
Fossils of this fish have been found in present-day Argentina.
Tooth fossils left behind by this fish suggest it was a flesh-eater like its modern relatives but may have also fed on plant materials.
13. Leedsichthys
| Name | Leedsichthys |
| Name Meaning | Leed’s Fish |
| Pronunciation | LEED-sik-thees |
| Era | Mesozoic – Jurassic |
| Classification | Actinopterygii, Pachycormiformes, & Pachycormidae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 30–33 meters (100–108 feet) |
| Weight | 15–30 tons (30,000–60,000 lbs) |
| Location | Europe and South America |
The largest bony fish still living today is the ocean sunfish which can grow to lengths of about 10 feet.
But the sunfish would have paled in comparison to Leedsichthys, which is often described as the king of bony fish.
Leedsichthys was a herring-like fish that grew to lengths of about 30 meters (100 feet) based on the most conservative estimates.
Reconstructing this fish’s appearance and true size has been difficult because some parts of its skeleton were made up of cartilage that was never preserved in the fossil record.
Like modern whales, Leedsichthys was a filter-feeder that survived on a diet of plankton.
Fossils of this fish have been discovered across different locations in Europe and South America.
12. Xenacanthus
| Name | Xenacanthus |
| Name Meaning | Alien Spine |
| Pronunciation | zee-NAK-an-thus |
| Era | Paleozoic – Carboniferous |
| Classification | Chondrichthyes, Xenacanthida, & Xenacanthidae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 1 to 2 meters (3 to 6.5 feet) |
| Weight | 5-10 lb (2.26-4.53 kg) |
| Location | Worldwide |
If the unicorn was real and it lived in the water, then it’d be the Xenacanthus.
This prehistoric freshwater shark lived during the Carboniferous Period and is known for the distinctive spine that projected from the back of its head like a unicorn’s horn.
The fish’s name, which translates as “alien spine,” is a reference to this bizarre spike on its head.
Experts have speculated that this spike had a potent venom like those of stingrays.
It was a primitive shark that looked nothing like modern sharks.
Instead, this fish had an eel-like body and swam like eels too.
It grew to a length of about two meters (6.6 feet).
Xenacanthus had bizarre “V”-shaped teeth adapted to crushing hard-bodied prey such as Crustaceans.
11. Stethacanthus
| Name | Stethacanthus |
| Name Meaning | Chest spine |
| Pronunciation | steh-THA-kan-thus |
| Era | Paleozoic – Carboniferous |
| Classification | Chondrichthyes, Elasmobranchii & Stethacanthidae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 2–3 meters (6.5–10 feet) |
| Weight | 9 kg (20 lbs) |
| Location | Worldwide |
Stethacanthus was a bizarre shark that lived from the Devonian to Early Carboniferous Period (between 390 and 320 million years ago).
It is also known as the anvil shark due to the flat, anvil-like shape of its dorsal fin.
The purpose of this fin is still a subject of debate, but experts think it probably served as an anchoring device for attaching to females during mating or anchoring to larger fishes.
Stethacanthus was roughly three feet long and weighed about 20 pounds on average.
The shape of the fish’s dorsal fin would have limited mobility in the water, prompting speculations that it was a bottom feeder that preyed on small fish and cephalopods.
10. Enchodus
| Name | Enchodus |
| Name Meaning | Spear-tooth |
| Pronunciation | en-KOH-dus |
| Era | Mesozoic – Late Cretaceous |
| Classification | Actinopterygii, Aulopiformes, & Enchodontidae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 1.7 meters (67.8 inches) |
| Weight | 9.07–11.24 kg (20–25 lbs) |
| Location | North America, Europe, Africa, and Asia |
The saber-toothed cats are large terrestrial carnivores that lived during the Pleistocene Epoch.
Several million years before they evolved, a different type of saber-toothed carnivore lived in oceans across the world.
The Enchodus had long fangs that measured over six centimeters (2.4 inches) in its front jaw.
Nicknamed the “saber-tooth herring,” Enchodus was more closely related to the salmon.
This five-foot-long predator fish fed on slippery prey like fish as well as marine invertebrates such as cephalopods.
While the fangs were effective for catching prey, the fish didn’t have chewing teeth, so it probably fed by swallowing its prey whole.
9. Eusthenopteron
| Name | Eusthenopteron |
| Name Meaning | Well-built fin |
| Pronunciation | yoo-STEN-op-tuh-ron |
| Era | Paleozoic – Late Devonian |
| Classification | Sarcopterygii, Tetrapodomorpha, & Tristichopteridae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 2.1 meters (6.9 ft) |
| Weight | N/A |
| Location | North America and Europe |
Eusthenopteron was lobe-finned fish with a streamlined body very similar to the shape of a torpedo or missile.
This fish which lived during the Devonian Period, is popular for its close relationship with tetrapods.
It was once considered the first fish species to venture out of the water onto land.
While this has been disproved, Eusthenopteron is still considered an important link between fish and early tetrapods because it developed features that would eventually evolve into legs.
The Eusthenopteron’s detention is also similar to that of the early tetrapods, and it had internal nostrils as well.
The long-bodied fish reached lengths of about six feet and was an efficient swimmer. The broadly shaped skull of this fish had numerous sharp teeth for catching and killing prey.
8. Dunkleosteus
| Name | Dunkleosteus |
| Name Meaning | Named after David Dunkle, a former curator at the Cleveland Museum of Natural History |
| Pronunciation | DUNK-lee-oh-STEE-us |
| Era | Paleozoic – Late Devonian |
| Classification | Placoderm, Arthrodira, Dunkleosteidae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 4.1–10 meters (13–33 feet) |
| Weight | 2-5 kilograms (4.4–11 pounds) |
| Location | North America, Europe, and Africa |
The placoderms were the most dominant fish species during the Devonian Period, and the Dunkleosteus was one of the largest and best-known members of this group.
The heavily armored fish lived during the Late Devonian Period between 382 and 358 million years ago.
Length estimates for the different species of this fish range between 4.1 and 10 meters (13–33 feet).
One of the most distinctive features of this massive fish was that it had bony plates in its jaws instead of regular teeth.
This allowed it to deliver an enormous bite force of more than 4,000 Newtons.
It was an apex predator of the Devonian seas and preyed on a variety of animals, including ammonites and other placoderms.
7. Dipterus
| Name | Dipterus |
| Name Meaning | Two Wings or Double Wing |
| Pronunciation | DIP-tuh-rus |
| Era | Paleozoic – Late Devonian |
| Classification | Sarcopterygii, Dipnoi, & Dipteridae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 30–90 centimeters (12–35 inches) |
| Weight | 27–89 grams (1–3 oz) |
| Location | Europe, North America, and Africa |
Dipterus was a genus of primitive lungfish that lived in Europe and North America during the Devonian Period.
The 35 centimeters (14 inches) long fish looked like modern species of lungfish.
Like its living relatives, the Dipterus, it had both lungs and gills, which made it possible to breathe inside and outside water.
But the Dipterus’ gills were more developed, while the lungs were more primitive compared to that of modern lungfish.
Dipterus probably spent more time in shallow freshwater ecosystems.
Dipterus also showed other primitive features, such as the presence of two dorsal fins and a tail similar to that of lobe-finned fishes.
It also had a tough, bony armor with tooth plates similar to that of placoderms.
6. Haikouichthys
| Name | Haikouchthys |
| Name Meaning | Haikou fish from Ercaicun |
| Pronunciation | HI-koo-ik-thys |
| Era | Paleozoic – Cambrian Period |
| Classification | Myllokunmingiida, Myllokunmingiidae, & Haikouichthyida |
| Diet | Carnivorous |
| Height | N/A |
| Length | 2.5 centimeters (1 inch) |
| Weight | N/A |
| Location | China (Asia) |
Haikouichthys was a primitive fish that lived 518 million years ago.
This was during the Cambrian explosion when life in the ocean was just starting to evolve into new forms.
Haikouichthys was one of the earliest fish to ever evolve and also one of the oldest vertebrates.
It was one of the most advanced creatures in the Cambrian seas and the first marine creature with a distinct head and tail.
This primitive fish measured about 2.5 centimeters (1 inch) long, with a dorsal fin running along the entire length of its body from the back of the head to the tail.
The fin also curves all the way round to the rear underside of its body.
The Haikouichthys had between six and eight fins for breathing in the water.
Haikouichthys is an extinct genus of primitive fish that lived during the Cambrian Period, approximately 518 to 516 million years ago.
It holds significance as one of the earliest known vertebrates in the fossil record.
5. Lepidotes
| Name | Lepidotes |
| Name Meaning | Scale or Scaly |
| Pronunciation | LEH-pi-do-tees |
| Era | Mesozoic – Jurassic |
| Classification | Actinopterygii, Lepisosteiformes, & Lepidotidae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 30 to 60 centimeters (12 to 24 inches) |
| Weight | N/A |
| Location | Europe, North America, and Asia |
Lepidotes was a type of ray-finned fish related to modern-day carp.
It lived in freshwater and shallow marine ecosystems of Europe during the Jurassic Period.
The most distinctive feature of this fish was the possession of jawbones detached from their jugal bones.
Lepidotes were one of the earliest fish species with this feeding adaptation, which made it possible for them to stretch their jaws into a tube for sucking in prey.
They also had densely packed peg-like teeth suitable for crushing hard-shelled animals such as mollusks.
Lepidotes were also prey for larger animals, such as spinosaurid dinosaurs like the Baryonyx.
4. Titanichthys
| Name | Titanichthys |
| Name Meaning | Titan fish |
| Pronunciation | tye-TAN-ik-thys |
| Era | Paleozoic – Late Devonian |
| Classification | Placoderm, Arthrodira, & Titanichthyidae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 6–9 meters (20–30 feet) |
| Weight | 3.5 tons (7700 lbs) |
| Location | Worldwide |
Titanichthys was one of the biggest animals of the Devonian Period.
It was a placoderm, a member of a group of armored fish that were quite common in the shallow seas of the Devonian Period.
Titanichthys grew to a fearsome length of up to 10 meters, which means it was almost the same size as the famous Dunkleosteus.
It also had a large, flattened body covered in bony plates.
But Titanichthys was probably not an apex predator like the Dunkleosteus.
That’s because it had wide gaping jaws without a sharp, biting surface.
The Titanichthys was most likely a suspension or filter feeder that fed by swimming through the water with its mouth open to capture plankton and other small prey.
This is quite similar to the feeding habit of basking sharks.
3. Piranhamesodon
| Name | Piranhamesodon |
| Name Meaning | Mesozoic biting fish |
| Pronunciation | pr-aa-nuh-ma-suh-daan |
| Era | Mesozoic – Jurassic |
| Classification | Actinopterygii, Pycnodontiformes, & Piranhamesodon |
| Diet | Carnivorous |
| Height | N/A |
| Length | 7.1 cm (2.7 inches) |
| Weight | N/A |
| Location | Germany (Europe) |
Piranhamesodon lived during the Jurassic Period, about 152 million years ago).
Although relatively small, this fish would have terrorized other fishes in its ecosystem.
It had serrated teeth similar to the dentition of modern piranha.
This is a trait not seen in any of the Piranhamesodon’s closest relatives, known for their flat-crushing teeth.
Piranhamesodon is also the first bony fish with this type of sharp serrated fish.
It had a weird and peculiar feeding habit that involved nibbling on the fins of other fishes.
Scientists have found other fish that were likely victims of the Piranhamesodon.
These fish had strange flesh wounds and evidence of shearing bites that appear to have been made by the flesh-slicing teeth of the Piranhamesodon.
2. Megalodon
| Name | Megalodon |
| Name Meaning | Gian Tooth |
| Pronunciation | MEG-uh-loh-don |
| Era | Cenozoic – Neogene |
| Classification | Chondrichthyes, Lamniformes, Otodontidae |
| Diet | Carnivorous |
| Height | N/A |
| Length | 15 to 18 meters (49–59 feet) |
| Weight | 65 metric tons (about 143,000 lbs) |
| Location | North and South America, Europe, Africa, and Asia |
The Megalodon belongs to the genus Carcharocles, but the specific name of this fish is more popular.
This prehistoric shark, known mainly from tooth fossils, is considered the largest and most ferocious predator of the ancient seas.
It lived during the Miocene and Pliocene epochs.
Megalodon was a superpredator that reached lengths of over 20 meters (67 ft) and a mass of over 103 tons.
Given its size, this massive fish would have had to consume close to 100,000 kcal of food per day.
The Megalodon’s diet included whales, seals, and giant sea turtles.
With a bite force higher than any other animal, living or extinct, the megalodon would have been able to take on any marine animal in the ancient Cenozoic seas.
1. Tiktaalik
| Name | Tiktaalik |
| Name Meaning | Large Freshwater Fish |
| Pronunciation | tik-TAH-lik |
| Era | Paleozoic – Late Devonian |
| Classification | Sarcopterygii, Tetrapodomorpha, Stegocephali |
| Diet | Carnivorous |
| Height | N/A |
| Length | 2–3 meters (6.5–10 feet) |
| Weight | 100 kg (220 lbs) |
| Location | Canada (North America) |
Tiktaalik is a special kind of prehistoric fish because it occupies an important evolutionary position in the transition from aquatic to terrestrial life.
It lived during the Late Devonian Period and had many features similar to the early tetrapods (four-legged animals).
Although it still had scales and gills like other bony fishes, Tiktaalik had a flattened triangular head with fins reinforced with interior bones.
This would have allowed Tiktaalik to hold its body up with its fins like the tetrapods.
Tiktaalik lived in swamps and may have been capable of spending some time on land or even crossing from one swampy pond to the other.
It has been nicknamed the “fishapod” due to these intermediate characteristics.
Sources
- https://en.wikipedia.org/wiki/Rhizodus
- https://en.wikipedia.org/wiki/Megapiranha
- https://www.science.org/content/article/ancient-fish-was-bigger-whale-shark-and-faster-scientists-ever-imagined
- https://australian.museum/learn/animals/fishes/xenacanthus/
- https://en.wikipedia.org/wiki/Enchodus
- https://www.fossilguy.com/gallery/vert/placoderm/dunkleosteus/index.htm
- https://www.britannica.com/animal/Eusthenopteron
- https://www.britannica.com/animal/Dipterus
- https://en.wikipedia.org/wiki/Haikouichthys
- https://en.wikipedia.org/wiki/Lepidotes
- https://www.cell.com/current-biology/fulltext/S0960-9822(18)31208-9
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