The Depths Under The Blue

Our Earth formed around 4.5 billion years ago and throughout the cycle of evolution, we’ve documented a variety of different flora and fauna from different periods on land and water, mostly vertebrates and invertebrates that lived on land. The existence of such organisms exists in fossil records unearthed by palaeontologists and archaeologists today. But even today there are so many secrets that are yet to be unearthed that lie in the depths of the ocean.

Abhidyu Ajila
6 min readMay 25, 2022

Our world as we know it has been a cradle for evolution and throughout the years we’ve seen many species of animals and plants engraved on our planet in fossil records. Throughout the ages, the earth has seen very peculiar creatures walk or swim on our planet, creatures that are completely erased from our planet. There were a variety of creatures that existed back in the day that just writing about them makes me go starstruck!!, well that’s what I bring here, talk about the evolution of creatures and most importantly our planet and how’s it evolved into something complex from the first organisms rising from the oceans to us humans polluting the very first place all living organisms came to land, terrifying, isn’t it?

Well, I’m here to talk about the treasures that used to dwell under our deep blue oceans of ours.

The timeline for our article starts at a little period known as the Devonian.

Devonian Period

Also called the “Age of Fishes", named after Devon in England where the rocks from this period were studied. the Devonian period saw the rise of adaptative radiation that saw the rise of spore-bearing plants on dry land which made forests as well as the rise of seed-bearing plants. fauna also started to expand on land but the Devonian was well known for its abundance of marine life.

Picture credit: Britannica

The period was well known for abundant species of marine life under the Devonian oceans. The most impressive animal from this period without a doubt will be dunkleosteus terrelli, which grew 8.8 meters and weighed 4 tons in weight making them the largest placoderms ( jawed fish) to ever exist.

Picture Credit:

Found in the waters of modern-day North America, Europe, and Morocco, they had an armoured exterior that made them slow swimmers but this must have been compensated with the bite force of 7,400 N bringing them into the league of modern-day crocodiles and Tyrannosaurs Rex.

Carboniferous Period

Around 358 million years ago, the Carboniferous period occurred which till its end was home to swamps and large deposits of coal hence named “Carboniferous”, the Carboniferous was well known to be the age of amphibians due to amphibians being the dominant land vertebrates.

Picture Credit: Britannica

Sadly, the Carboniferous period is not necessarily well known to be abundant in marine life but there were still some marine species that dominated marine life one of them was Dracopristis hoffmanorum, also called “dragon shark” due to its spines on its fins, this carboniferous shark grew around 6ft long.

Dracopristis Hoffmanorum forum picture credit: Machan-forest

The Permian

Picture Credit: Britannica

Named after the region of Perm in Russia by geologist Dr Roderick Murchison, The Permian witnessed the diversification of amniotes which were divided into synapsids (mammal and mammal-like) and sauropsids (reptiles and birds). Dominated by the supercontinent Pangea, the Permian period was home to a unique group of flora and fauna out of which one such was Helicoprion.

Helicoprion Picture credit: GeologyIN

Also known as buzzsaw sharks due to their teeth whorls, these palaeozoic sharks grew up to 8 meters ( 26.2ft) and mostly fed on soft-bodied prey as their narrow mouth and jaw structure might have made it difficult to eat hard-bodied prey, researchers have postulated that their teeth whorls might have helped them grab on to hard-shelled prey like nautilus after which the teeth whorls might have pulled their preys soft bodies out of them.

Helicoprion jaw motion picture credit: Wikipedia

The Jurassic

The Jurassic period succeeded the Triassic period roughly 200 million years ago, the term "Jurassic" was named after the Jura mountains, a small mountain chain which lines between Switzerland and France.

Picture Credit: Geology Page

The name Jurassic is probably well-known thanks to the movie franchise"Jurassic Park" and John Hammond along with his attraction filled with dinosaurs exhibiting different temperaments. Well, they didn't have a marine reptile in the previous park but the one which exist and would have been one hell of an attraction would have probably been the plesiosaur Liopleurodon

Liopleurodon Picture Credit: Wikipedia

Estimated to be 7 meters (21 feet) long and weighed around 1.5 tonnes it was massive carnivorous plesiosaur that used it's nostrils to sense smell and scan their surroundings.

The Cretaceous

Picture Credit: Australia Museum

The Cretaceous Period succeeded the Jurassic Period and was the longest period from 144 million years to 66 million years. This was also the period where my favorite dinosaur roamed the Earth Tyrannosaurus Rex well, back to the topic, the biggest tyrant in the waters of the Cretaceous period is surely without a doubt the Mosasaurus

Mosasaurus hoffmani Picture Credit:

Mosasaurus was one of the largest predators of the Cretaceous waters measuring around 18 meters long ( 59ft) in lenght and weighed around 14,000 kgs, it is presumed that had a bite force of around 16000 psi making it a dangerous bite and a not so happy ending for the prey, yikes!!.

After Cretaceous

After the age of dinosaurs, the most terrifying predator that existed was the Megalodon

Megalodon Picture Credit: nhm.

This massive predator would have given the mosasaurus previously mentioned a hard time if these two faced each other head-on, measuring around 60ft and weighing around 60 tons it was the biggest and most dangerous predator of its time. Just like their modern-day counterparts, they had a strong jaw and teeth made for tearing flesh and with a terrifying deadly bite force of 40,000 psi with that kind of power, no wonder every meal was easy.

Picture Credit: Wikipedia

Well here are some of the marine treasures of the past and if not the most uniquely diverse megafauna that used to exist back from the Devonian till the Pliocene. It’s not that beautiful megafauna don’t exist today this article’s focus was on some prehistoric marine megafauna that I thought deserve some recognition. Hope you’ll enjoy the article. As always stay safe and hope y’all have a great day ahead. 👻

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Abhidyu Ajila

A zoology student who talks animals, conservation, evolution and geography