The 60-million-year period spanning from 419 to 358 million years ago (Ma) was characterized by a remarkable boom in the Earth’s fauna.
Aquatic life flourished during this period, so much so that it has been nicknamed the “Age of Fishes.”
Named after the city of Devon in South West England, where rocks from this period were first studied, the Devonian Period is characterized by a significant evolutionary radiation of life on earth — both in the water and on land.
Different kinds of fish, from armored placoderms to cartilaginous shark ancestors, emerged during the Devonian.
Other marine animals, such as the eurypterids that evolved earlier, continued to flourish during the Devonian and were among the top predators of the period.
As life continued to boom in the ocean, terrestrial life began to take a more familiar form and Earth’s first forest developed.
The Devonian ended with the emergence of the first four-legged animals to colonize Earth’s terrestrial ecosystems — paving the way for the age of amphibians.
The Devonian Period is one of the most productive periods of Earth’s history that saw the emergence of several remarkable animal species.
In this article, we’ll list 15 of these animals, exploring some of their most unique attributes.
15. Osteolepis
| Name | Osteolepis |
| Name Meaning | “Bone scale” |
| Pronunciation | Os-te-o-lep-iss |
| Classification | Tetrapodomorpha, Osteolepiformes, & Osteolepididae |
| Diet | Carnivorous |
| Length | 20 centimeters (7.9 inches) |
| Location | Scotland (Europe) |
Osteolepis was a lobe-finned fish that lived in the primitive Orcadie Lake located in Northern Scotland during the Devonian Period.
This small fish was only 20 centimeters (7.9 inches) long, and its body was covered in large scales.
Osteolepis had a bony head covered in large scales and plates.
On top of this, there was a layer of spongy material known as cosmine, which had canals connected to sensory cells in the fish’s body.
The genus name, which translates as “bone scale,” is a reference to this scaly appearance.
Using the sensory cells in its scales, the Osteolepis could detect changes in the water pressure caused by the presence of other aquatic animals.
Osteolepis used this to hunt prey and avoid predators in the water.
14. Rhyniognatha
| Name | Rhyniognatha |
| Name Meaning | “Snout-jawed” |
| Pronunciation | rye-nee-o-GNA-tha |
| Classification | Arthropoda, Rhyniognatha |
| Diet | Carnivorous |
| Length | Unknown |
| Location | Europe |
Rhyniognatha was an insect species that lived during the Early Devonian Period about 400 million years ago.
It is considered the oldest insect ever discovered and possibly the earliest flying insect to have ever evolved.
Only the partial head and preserved mouthparts of this insect are known, which has led to controversies about its true appearance and classification.
Some experts also think Rhyniognatha was probably not a flying insect.
Instead, they classify it as a myriapod, which means it is more closely related to other arthropods, such as millipedes and centipedes, instead of insects.
13. Acanthostega
| Name | Acanthostega |
| Name Meaning | “spiny roof” |
| Pronunciation | A-can-fo-stay-gah |
| Classification | Sarcopterygii, Tetrapodomorpha, & Stegocephali |
| Diet | Carnivorous |
| Length | 60 centimeters (24 inches) |
| Weight | 2.2–4.4 kilograms ( 5–10 pounds) |
| Location | Greenland (North America) |
Acanthostega was a primitive tetrapod considered one of the first animals to evolve four distinct limbs.
Despite having limbs, it was still a fully aquatic animal.
The limbs had webbed digits and were better adapted to paddling rather than bearing weight on land.
Acanthostega also had fish-like shoulders as well as tail fins and scales.
It lived in shallow swamps and hunted by biting prey at or near the water’s edge instead of the suction-feeding habits of most fish species.
Acanthostega had both gills and lungs.
This suggests that it could breathe both in the water and outside.
However, the poorly developed rib of this species suggests that it could not breathe air for extended periods.
12. Homosteus
| Name | Homosteus |
| Name Meaning | “bone-like” |
| Pronunciation | hoh-MOH-stey-us |
| Classification | Placodermi, Arthrodira, & Homostiidae |
| Diet | Filter-feeder |
| Length | 30 centimeters (12 inches) |
| Location | Europe and North America |
Homosteus was an armored fish that lived during the Middle Devonian Period.
Fossils of this fish have been found in parts of Europe and North America (Canada).
Discovered as far back as the 1830s, the Homosteus is one of the first fossil species to be classified as a placoderm.
It was a filter feeder that mainly ate organic matter and microorganisms in benthic environments.
Homosteus specimens recovered from the Old Red Sandstone of Scotland were found to contain high levels of radioactivity.
Experts think they ingested radioactive sediments in life.
Many specimens were found with enough radiation exposure to cause negative side effects.
However, it isn’t clear how much this would have affected them in real life.
11. Climatius
| Name | Climatius |
| Name Meaning | “gradation” |
| Pronunciation | Cli-mat-e-us |
| Classification | Acanthodii, Climatiiformes, & Climatiida |
| Diet | Carnivorous |
| Length | 7.5 centimeters (3 inches) |
| Location | Europe and North America |
Climatius was a species of spiny cartilaginous fish that lived in North America and Europe during the Devonian Period.
It belonged to the class Acanthodii, which means it is considered a primitive ancestor of modern cartilaginous fish species such as sharks and rays.
Climatius was a relatively small fish, with an average length of about 7.5 centimeters (3 inches) on average.
It was an active swimmer that preyed on small marine animals such as small fish and crustaceans.
The upper jaws of this fish had no teeth, but the lower jaws were lined with several sharp teeth.
Given its small size, Climatius would have been easy prey for larger marine animals.
Climatius had fifteen sharp spines on its body, which would have protected it against predators.
10. Bothriolepis
| Name | Bothriolepis |
| Name Meaning | “Trench scale” |
| Pronunciation | Bo-free-oh-lep-is |
| Classification | Placodermi, Antiarchi, & Bothriolepidae |
| Diet | Detritivore |
| Length | 30 centimeters (12 inches) |
| Location | Worldwide |
Bothriolepis was one of the most abundant armored fish species (placoderm) of the Devonian Period.
It lived from the middle to late Devonian Period and had a widespread distribution that covered virtually all paleo-continents.
Most species of this fish lived in near-shore marine and freshwater ecosystems.
They averaged 30 centimeters (12 inches) in length, but the largest Bothriolepis species was up to 170 centimeters (67 inches).
It had a flattened body and a large mouth but was not an active predator like the larger placoderms.
Bothriolepis was a freshwater detritivore, which means it ate decomposing organic matter in the bottom sediments of the freshwater rivers and lakes where it lived.
It also ate small microorganisms and algae.
9. Pterygotus
| Name | Pterygotus |
| Name Meaning | “Finned one or wing animal” |
| Pronunciation | Teh-ry-go-tus |
| Classification | Chelicerata, Eurypterida, & Pterygotioidea |
| Diet | Carnivorous |
| Length | 1.75 meters (5.7 feet) |
| Location | Australia, Europe, North America, South America |
Pterygotus was one of the largest and most successful predators of the Devonian Period.
Fossils of the Pterygotus have been found in Australia, Europe, and North and South America, which suggests that it had a widespread distribution.
This massive scorpion-like arthropod (eurypterid) evolved earlier during the Silurian but was alive until the end of the Devonian Period.
It grew to a length of up to 1.75 meters (5.7 feet) on average, making it one of the largest arthropods of the Devonian.
Pterygotus was an active predator.
The species is renowned for its sharp vision and enlarged claws, which helped in grasping prey.
8. Pteraspis
| Name | Pteraspis |
| Name Meaning | “Wing shield” |
| Pronunciation | Teh-rass-pis |
| Classification | Pteraspidomorphi, Heterostraci, & Pteraspidiformes |
| Diet | Carnivorous |
| Length | 20 centimeters (7.9 inches) |
| Location | Europe, South America, North America |
Pteraspis is a genus of jawless fish that lived in Europe and the Americas during the Devonian Period.
The primitive fish had fins except its lobed tail but was an efficient swimmer.
It had a streamlined body and stiff wing-like protrusions on its side that made up for the lack of pectoral fins and helped with locomotion.
Like other primitive fish of the Devonian, the upper body of the Pteraspis was covered in rounded armored plates.
The fish also had stiff spikes on its back that provided extra protection against predators.
Pteraspis was a freshwater species, but a few species lived in Marine ecosystems as well.
The fish was approximately 16 centimeters (6.5 inches) in length and fed mainly on plankton and other tiny animals in the Devonian waters.
7. Cladoselache
| Name | Cladoselache |
| Name Meaning | “Branch-toothed shark” |
| Pronunciation | Clay-do-sel-ah-kee |
| Classification | Chondrichthyes, Cladoselachiformes, & Cladoselachidae |
| Diet | Carnivorous |
| Length | 2.0 meters (6.6 feet) |
| Weight | 9–13 (20–30 pounds) |
| Location | North America |
Cladoselache was a shark-like cartilaginous fish that lived in North America towards the end of the Devonian Period.
It is considered a primitive ancestor of modern sharks and rays, with physical attributes similar to that of modern white sharks (lamnid sharks).
Cladoselache is one of the best-known shark ancestors, thanks to an abundance of well-preserved fossils.
In fact, some fossils of this fish include traces of skin, muscle fibers, and internal organs, which is quite unusual for a cartilaginous fish.
The largest Cladoselache fossil found so far is about two meters (6.6 feet) long.
Like its modern relatives, Cladoselache was an active predator whose diet included bony fishes, marine arthropods, and conodonts.
6. Adelophthalmus
| Name | Adelophthalmus |
| Name Meaning | “Hidden eye”” |
| Pronunciation | a-DEL-o-thal-mus |
| Classification | Chelicerata, Eurypterida, & Adelophthalmoidea |
| Diet | Carnivorous |
| Length | 4–32 centimeters (1.6–12.6 inches) |
| Location | Worldwide |
Adelophthalmus is considered one of the longest-lived eurypterids (sea scorpions).
It had a temporal range of over 120 million years, starting from the Early Devonian to the Permian Period.
Adelophthalmus also had a widespread distribution that covered virtually all continents, making it one of the most widely distributed eurypterid species.
It was a relatively small eurypterid.
The largest species was about 32 centimeters (12.6 inches) long, while the smallest only measured four centimeters (1.6 inches).
Adelophthalmus was one of the last swimming eurypterids (others that lived after it walked on the bottom sediment).
It hunted small prey such as insects, brachiopods, millipedes and worms.
5. Dipterus
| Name | Dipterus |
| Name Meaning | “Two wings” |
| Pronunciation | Dip-teh-rus |
| Classification | Sarcopterygii, Dipnoi, Dipteriformes |
| Diet | Carnivorous |
| Length | 35 centimeters (14 inches) |
| Location | Europe and North America |
Dipterus is a prehistoric lungfish that lived in Europe and North America during the Devonian Period.
It looked a lot like modern lungfish but had tooth-like plates in its mouth instead of actual teeth.
Dipterus was about 35 centimeters (14 inches) long on average.
This primitive lungfish had all its fins separated instead of the fused dorsal, caudal, and anal fins of modern relatives.
Dipterus lived in the shallow waters of the Devonian and was capable of surviving out of water for long periods.
However, it still had gills for breathing underwater, and its lungs were not as well-adapted as that of other lungfish species that evolved later.
This suggests that the Dipterus still lived a fully aquatic lifestyle but could survive out of water for short periods.
4. Ichthyostega
| Name | Ichthyostega |
| Name Meaning | “Fish roof” |
| Pronunciation | Ik-fee-o-stay-gah |
| Classification | Tetrapodomorpha, Stegocephali, & Ichthyostegidae |
| Diet | Carnivorous |
| Height | Unknown |
| Length | 1.5 meters (4.9 feet) |
| Weight | 22.6 kilograms (50 pounds) |
| Location | Greenland (North America) |
Ichthyostega is one of the best-known transitional animals of the Devonian Period.
This four-limbed animal shows both tetrapod and fish-like features.
It lived during the Late Devonian Period and was one of the first animals with true weight-bearing limbs that may have supported terrestrial locomotion.
The hind limbs had seven digits and were well-developed compared to the forelimbs.
The Ichthyostega’s forelimbs were used like paddles for steering in the water, and its long tail would have helped with locomotion as well.
On land, the 1.5-meter-long (4.9 feet) tetrapodomorpha likely moved by dragging its body like mudskippers and seals do.
3. Cephalaspis
| Name | Cephalaspis |
| Name Meaning | “Head shield” |
| Pronunciation | Seff-ah-lass-pis |
| Classification | Osteostraci, Cephalaspidiformes, & Cephalaspidae |
| Diet | Detritivore |
| Length | 20 –30 centimeters (7.9–11.8 inches) |
| Location | Europe and North America |
Cephalaspis was a trout-sized jawless fish that lived during the Early Devonian Period.
It was one of the most common fish of the Devonian Period, with several fossils found in various locations across Europe and North America.
Cephalaspis had a massive armored head with a mouth located on the underside of its head.
This suggests that it was a bottom feeder that strained food from the bottom sediments of the freshwater streams where it lived.
Cephalaspis could use its plow-like head to stir up bottom sediments in order to expose hidden prey.
Given its small size, this fish was also prey to the larger predators that lived during this period, such as the placoderms and sea scorpions.
The heavily armored head of the Cephalaspis was an adaptation to protect this fish against these predators.
2. Tiktaalik
| Name | Tiktaalik |
| Name Meaning | “large freshwater fish” |
| Pronunciation | Tik-taa-lik |
| Classification | Sarcopterygii, Tetrapodomorpha, Elpistostegalia |
| Diet | Carnivorous |
| Length | 1.25–2.75 meters (4.1–9.0 feet) |
| Weight | 100 kilograms (220 pounds) |
| Location | Canada (North America) |
The Devonian Period is characterized by the emergence of vertebrate animals on land, and the Tiktaalik was probably one of the Devonian animals that best demonstrates this transition.
This genus of lobe-finned fish shows many features similar to that of tetrapods (four-legged animals).
The most notable of these is the presence of sturdy interior bones in its fins.
Experts believe the Tiktaalik used this limb for support like tetrapods do.
Tiktaalik was largely aquatic, but it was probably capable of propping itself up in shallow waters.
It was a large fish that grew to a length of up to 2.75 meters (9.02 feet).
One of the most distinctive features of the Tiktaalik was its large, triangular head.
The head was flattened and looked more like that of a crocodilian than a fish.
Tiktaalik fossils were unearthed in Arctic Canada, which suggests that it lived in North America during the Devonian.
1. Dunkleosteus
| Name | Dunkleosteus |
| Name Meaning | “Dunkle’s bone” |
| Pronunciation | Dun-kel-os-tee-us |
| Classification | Placodermi, Arthrodira, Dunkleosteidae |
| Diet | Carnivorous |
| Length | 4.1 to 10 m (13 to 33 ft) |
| Weight | 1- 4 tons (1,000 to 4,000 kilograms) |
| Location | North America, Europe and Africa |
The Dunkleosteus is one of the most famous animals of the Devonian Period.
This massive armored fish is the largest predator known from that period and one of the first apex predators to have ever existed.
It grew to a length of over 10 meters and weighed up to 1.4 tons on average.
Dunkleosteus lived in the open waters of North America, Europe, and Africa.
It was a type of Placoderm, a group of armored fish that dominated the Silurian and Devonian periods.
The Dunkleosteus is famous for its powerful jaws, which feature a specialized four-bar linkage mechanism for opening and closing.
This jaw structure allowed the Dunkleosteus to open and close its jaws quickly while delivering a massive bite with its plate-like teeth.
A bite force of up to 7,495 Newtons (1,685 pound-force) has been estimated for the Dunkleosteus, the highest of any living or fossil fish.
Sources
- https://en.wikipedia.org/wiki/Rhyniognatha
- https://www.britannica.com/animal/Ichthyostega
- https://en.wikipedia.org/wiki/Osteolepis
- https://en.wikipedia.org/wiki/Pteraspis
- https://en.wikipedia.org/wiki/Dipterus
- https://en.wikipedia.org/wiki/Homosteus https://www.nytimes.com/2023/03/04/science/chunky-dunk-fossil.html
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