Jaws In The Depths
Earth has been the playground of a plethora of organisms for millions and millions of years, it has been a provider giving the organisms that thrive with food and shelter. However, what Earth brought along with such amenities was also a competition in the name of “evolution”. The game itself has pretty simple rules, adapt to the changes around you or perish. Now, it does sound harsh but let me be specific, throughout history, there have been many events that coincided with certain levels of extinctions from the great dying during the Permian and the latest of them the Asteroid strike in the Gulf of Mexico 65 million years ago, cooking the dinosaurs to toast.
But those extinctions occurred at a specific time and were naturally occurring events. We humans on the other hand have taken matters into our own hands, taking some context out of “shallow ecology” and creating the Anthropocene, the new epoch or as I like to say “The Ending no one wants but the ending we deserve”. While many organisms have taken a hit toward extinction, sharks have probably got the worst going for them.
These intriguing predators have garnered a bad image due to movie depictions and the hunt for their fins hasn’t helped their cause either resulting in a decline in their populations from the small Scoliodon to the Whale Sharks. Readers, I’ll be taking you on a journey in time where we’ll learn about how sharks came to be, their evolution through time, and the recent threats to the largest fish in the ocean.
Sharks Of The Devonian
Life during the Devonian was somewhat different from the life we’re used to today. Imagine yourselves in the waters during the Devonian, named the age of fishes is an understatement when you realize the plethora of fish abundance during that period.
The Shark That Swam Naked
If you ever get a chance to get close to a shark, which I hope you don’t get too comfy around when it decides to use its chompers to get a bite off you, try touching its skin. While you rub your hand against it from its head towards its tail, you’ll feel a soft body but as you go backward you feel something harsh, that’s because sharks have placoid scales. What are placoid scales? Don’t worry about it, I’m here to tell you exactly what they are.
Placoid scales or dermal denticles as we call it are scales that cover over the sharks body, they are backward facing thus you feel something harsh the moment you touch the sharks body from the tail to the head region. Despite the cons here for us, this allows sharks of today to swim swiftly and at great speeds also protecting them from injuries.
But what if I tell you that a certain species never had such protection and literally swam naked?
Let me introduce you readers to the oddball here in Cladoselache, a shark that lived in the seas of the Devonian 370 million years ago and were fast predators like the modern-day Mako sharks. They were medium sized sharks about 4 foot long (1.2 metres long)
These sharks had something rather intriguing as they didn’t have the protection of placoid scales that we actually identify sharks with today. They also lacked claspers (an organ found in male sharks that helps transfer sperm) and had an unusual jaw that was attached to their skull unlike we see in modern-day sharks that have their jaws connected to the skull via help of various ligaments.
A Headgear For Attraction
Sexual dimorphism heavily influences the reproductive triumph of a species. If you take a look at birds, the males are more brightly feathered than females, let’s take a look at the Peafowl
Here, a clear representation can be seen of sexual dimorphism. Male peafowl have more vibrant feathers and a spectacular dance, but why? It’s to attract a mate, this is something that is not seen in fish. But what if I say that there was a shark that showed such an amazing sense of style, Meet the Stethacanthus, a Devonian shark-like holocephalian.
It is an intriguing-looking shark, isn’t it? These sharks had a peculiar dorsal fin that immediately catches the attention of anyone that looks at them. But the question is why that rings through your heads, I can see some of you readers scratching their heads. Don’t worry, I’ll answer it for you readers, that’s what I’m here for, getting back to this, stethacanthus had an interesting anomaly to it, it had an iron-shaped dorsal fin that was only a feature seen in males of these sharks and were probably used during courtship behavior.
Intriguing Tooth Shape
Permian was the period where our planet went through a drastic change. The rise of organisms since the Cambrian explosion was at its peak. The organisms that thrived during this period were quite an intriguing set of creatures. One such organism was Petalodus, a primitive shark that thrived during this period. Named after its sub triangular rhomboid teeth, this shark was named by Richard Owen in the 1840s.
It was supposedly a medium sized shark estimated to be around 3 to 5 metres and was said to be an efficient predator that had a vast dispersal from the continent of Laurusia till the North China region along the ancient Tethys Sea, possibly giving us an insight towards just how these predators adapted through million and millions of years perfecting their craft towards the art of predation.
The Freshwater Jaws
We all have an idea that sharks are exclusively found in seawater with certain exceptions, this entry is one of them, Triodus.
Triodus was a species of freshwater shark that existed from the late Carboniferous to the early Triassic period. The fossils found throughout Laurasian deposits and Western Gondwana land (modern-day Brazil) with specimens of teeth described of the species Triodus jordan.
Triodus as a species was described by their body morphology and teeth shape, Triodus jordan has been described by the presence of oval shaped base with their crowd constituting 3 cusps: 2 lateral and 1 median cusp that show an upward protrusion, with the median cusps being longer in length compared to the lateral cusps.
The Predatory Masterpiece
With a change in scenery, the early Miocene brought about the rise of the genus Otodus, a genus of sharks that comprised one of the most ferocious predatory fish of its time the Megalodon.
Otodus megalodon, was a shark species that existed during the Miocene and late Pliocene. With an average length of around 15 metres that could have possibly grown up to 18 metres similar lengths that the largest whale sharks alive. With no correct fossil evidence towards the length of these predatory giants, the only way these shark lengths are estimated by their teeth size.
This is a picture comparing a Megalodon tooth with a Great white tooth. Armed with rows of teeth that measured around 7 inches (17 inches) and a jaw that was around 2 to 3 metres wide, these predators had the perfect tools up their sleeves to become the most efficient predators of the Miocene.
Modern-day Sharks
Moving towards the modern-day Sharks, the diversification of this amazing fish has brought about a plethora of amazing fishes with a high degree of evolution throughout the years with respect to their eating habits and ecosystem.
Predatory Disguise
One of the most intriguing sharks in my opinion is the Wobbegong Shark Orectolobus maculatus.
Also known as the carpet shark, these sharks have a flattened stocky body, tail and some dermal lobes that act as bait for unsuspecting prey making them efficient predators in their domain. Found swimming throughout the Western Pacific waters along the coastal Australia with some species also found in the Japanese and South China sea.
Armed with sharp and enlarged fangs alongside an extendable jaw, wobbegongs can feast on multiple organisms of the likes of Crabs, Lobsters, molluscs such as octopus and other bony fishes and other small sharks.
A Shark Good That’s At Geometry?
When you take a look at the majority of sharks only one picture comes to mind, huge jaws and rows of sharp teeth. A chomp of a great white can take a large chunk of flesh off the body of its victim. But what if I tell you, there’s a shark that leaves a cookie shaped mark on its victim that doesn’t even kill it? If you guessed the name Cookie Cutter shark, you’ve guessed correctly, pat yourself on the back.
Named after their unique style of feeding, Cookie cutter sharks are small species of sharks that are found in warm tropical to temperate waters and don’t grow more than 18 to 20 inches or 50 cms.
They have a cigar shaped body with a good set of sharp teeth, but why is it called a cookie cutter shark? The answer lies within its name, this shark is well known to take off bits of meat off its prey allowing the prey to see another day. However, leaving a cookie shaped mark on its victim. Here’s an example of how it looks
So despite its small stature, it can give painful bites while taking some bits off your flesh alongside leaving a cookie shaped mark as a memento.
The Planktivore
One of the most intriguing sharks to have evolved throughout the years are Planktivorous in nature.
Let’s take the Basking Shark for an instance.
Basking Sharks (Cetorhinus maximus) are the second largest fishes that are found in a wide range of ocean waters average length of 36 feet (11 metres) with some individuals measuring at around 45 feet (13.7 metres) and weigh around 3.9 metric tonnes. However, these dimensions shouldn’t bother you, these behemoths are totally harmless unless you get whipped by their tail, jokes apart these guys are Planktivorous, i.e they feed on planktons and not on fishes and other bigger marine organisms.
So yeah, if swimming with Basking Sharks is on your bucket list you won’t have to worry about the shark, but probably your bank balance!!
An Odd Feeding Strategy?
Sharks are a group of organisms that are associated with predatory behavior at its finest. However, there’s one set member of this intriguing predatory fish who has a unique feeding strategy, Meet the Bonnethead Shark
Bonnethead sharks (Sphyrna tiburo) are one of the smaller hammerhead species and are the only documented sharks that are known to be omnivorous in nature. While many of you readers might be scratching your heads towards this somewhat intriguing fact on how a shark can be omnivorous? The answer lies in their diet composition. A Bonnethead sharks diet is primarily composed of seagrass (60%) while it also feeds on small crustaceans, squids and fish. Now a fun question for the readers, how does the Bonnethead digest the seagrass? Seagrass being a plant consists of cellulose that can be digested by herbivores thanks to their ability to absorb cellulose, a similar function takes place in Bonnetheads where an enzyme in the form of b-glucosidase in their guts helps them digest cellulose. Interesting right?
This was my take on the jaws in the depths of our oceans. There are so many more aspects to talk about these marvellous creatures that have fascinated me since childhood.
I hope you readers like this, if you would like to know more about such amazing creatures, if so do follow my medium to learn more about such organisms and the way they function.
