Before starting to describe the animals that dwelled during the Paleozoic era, I need to provide some background information about the era itself. In some texts, you will find the word “Paleozoic” written as “Palaeozoic” but it is totally fine. You can use those words interchangeably. Both of these words came from Greek which means “ancient life”.
Paleozoic was the time when Arthropods, fish, amphibians, mollusks, diapsids, and synapsids began to evolve. During the Paleozoic era, life began inside the ocean but eventually, some living creatures adopted to living on land. Not only animals but also some types of plants evolved from green algae and moved from water to land.
The environment of the Paleozoic was covered with the forest, which hosted the primitive plants such as the Lycophytes, Rhynia, Sawdonia, psilophyton, Sphenophytes, Progymnosperms, Ferns, Seed Ferns, and others.
The Paleozoic era ended with the greatest mass extinction which wiped out nearly 95% of the marine life; However, no one knows accurately what had caused the mass extinction. Some scientists speculate that the cause of the mass extinction was due to sudden drop of temperature or collision of extraterrestrial objects onto the planet.
Now, let’s learn what animals dwelled on this planet over 400 million years ago during the Paleozoic era.
Trilobites are marine creatures that belonged to extinct marine arthropods. They flourished during the early Paleozoic period and went extinct 245 million years ago. That means no humans saw these creatures, but thanks to their fossilized skeletons researchers had a chance to study them.
They mostly lived in shallow and muddy marine environments. Although some types of trilobites could float or swim, most of them remained under the rocks scavenging various organic organisms.
Some scientists believe that Trilobites originated in the present-day Siberia. Like some types of modern day bugs, trilobites could curl its body into a ball shape when they felt threatened.
Interestingly, 1500-year-old human settlements wore the fossilized remnants or Trilobites as an amulet.
Pikaia is considered as the oldest known chordates. It was wormlike animal which measured 2 inches (5 centimeters) long. Pikaia did not have a well-defined head. Although it vanished from the face of this earth millions of years ago, a creature that looks like it still lives in the present-day oceans. It is called Lancelet Branchiostoma.
It swam in the ocean during the Cambrian times. They made a series of zigzag bends and throw its whole body to move forward.
Some scholars believe that it is very much similar to the ancestors of backboned animals (vertebrates) which includes fish, birds, and mammals. Surprisingly, some people think that Pikaia might be the ancestors of humans.
Eurypterus were marine animals that belonged to the genus of Eurypterid, which includes living organisms known as “sea scorpions”. They were good swimmers, they even got a natural paddle which allowed them to move quicker.
In general, the size of Eurypterus was around 5 to 9 inches (13-23 cm) but the larger ones even reach to the length of 4.3 ft. (1.3m). The largest specimen of this Paleozoic animal is currently displayed at the Paleontological Research Institute of New York.
Eurypterus one of the well-studied animals of Paleozoic thanks to the well-preserved fossils. Although they are mostly known as marine animals, some scholars believe that Eurypterus might have spent some intervals of time on land. Also, Eurypterus were the close relatives of scorpions and other arachnids.
Dunkleosteus was one of the largest and the most fearsome fish that swam in the oceans during the Paleozoic era. It is being categorized as a predator because it had an aggressive look with pretty strong jaws that could tear apart any other fish. Apart from its fearsome look, the fish had a huge body that reached up to 20 feet ( 7 m).
Another interesting thing about Dunkleosteus was that it had a pretty large head with a hard shell around it. Scholars think that hard-shell allowed the fish to use it as an armor to protect its head; However, the rest of the body did not have that shell, therefore, the fish was flexible enough to swim and catch its prey quickly.
Cladoselache is considered the earliest sharks of this planet. Their size is estimated to be over 3ft (1m) long. Compared to Dunkleosteus, cladoselache had a small size and probably they were preyed upon by Dunkleosteus. Luckily, Cladoselache was a good swimmer because their forked tail allowed them to move quickly.
Interestingly, some Cladesolache fossils were whole and even some fossils had the remnants of internal organs. In one of the fossils, remnants of smaller fish were found inside cladesolache. This means they were a predator for a smaller fish.
Another interesting trait is that a male cladoselache did not have internal reproductive organs; However, scholars believe that they managed to reproduce somehow.
Akmonistion was one of the earliest types of sharks that are characterized by its dorsal fin. Their dorsal fin is known as “spine-brush complex”. Additionally, Akmonistion was thought to be a slow and stable swimmer. But whenever it saw an agile prey, it increased its speed and captured them by utilizing their sharp teeth.
To get to know this Paleozoic animal in detail, you may refer to the scientific study conducted by M.I. Coates and S.E.K. Sequiera.
One of the animals of the Paleozoic era was Pederpes. It belonged to the earliest group of Tetrapods. Pederpes was thought to be one of the earliest “terrestrial tetrapods”.
When it was first discovered in Schotland in 1971, it was classified as lobe-finned fish. However, it was reclassified as a primitive tetrapod in 2002 by Jennifer Clack.
Pederpes feet were forward-facing rather than outward. That indicates that they adapted to the land and walked on it. The structure of their ear indicate that their hearing was functional underwater. Some scholars speculated that they hunted and stayed inside water most of their time.
Some animals of the Paleozoic era were the land dwelling amphibians. One of them was Edaphosaurus. It was one of the earliest grass-eating animals of the Paleozoic period. One of the notable body parts of Edaphosaurus was a tall dorsal sail. The functions of those sails are still unknown.
The first Edaphosourus fossil was found in North America, more specifically, in Texas Red Beds. Some fossils were also found in Central Europe and Eastern Germany.
Edaphosaurus means “pavement lizard”; However, compared to modern-day lizards, they were large. Some of the large ones were estimated to be 11.5ft (3.5 m).
Titanophoneus is another fearsome animal of the Paleozoic era. Its name means “titanic murderer”. The first remnant of the Titanophoneus is found in Russia. They were quite large. Their sizes reached up to 20 feet (6 m) when measured from head to tail.
Scholars think that Titanophoneus were omnivorous (eats both meat and plants) because the recovered remnants of skulls indicate that they had canines and sharp teeth. That means they might have hunted smaller living animals for food.
Inostrancevia belongs to the extinct genus of carnivorous therapsids. They were carnivorous animals which means they hunted and eat herbivorous (plant-eating), omnivorous (plant-and meat-eating) and other carnivorous (meat-eating) animals.
The overall length of Inostrancevia reached up to 11.5 feet (3.5 m) and their body mass estimated to be 660 lbs (300kg). The first fossil of Inostrancevia was found in the Arkhangelsk oblast of Russia.
These were the 10 animals of the Paleozoic era. Of courses, it is not a complete list. There are so many other interesting animals from this era. We only chose the 10 to give a general idea of the animal life of the Paleozoic era. If you want to add something, you may share them in the comments section.