Chapter 2: The Cambrian Explosion
Hello again everyone and welcome to chapter 2, of my series and this is where the story should start getting interesting, as we enter the Paleozoic Era, so without further ado, let us dive in.
This is Earth 518 million years ago during a time known as the Cambrian, the first period of the Paleozoic Era. At this time a supercontinent, known as Gondwana covers the southernmost part of Earth and makes up what will one day be the continents of South America, Africa, Australia, and Antarctica. To the North, sits fragments that will one day be North America and parts of Asia; these particular landmasses, sit at the Equator. The landscapes here are barren and devoid of much of anything, besides sand and rocks baking in the blistering sun. This however, is not the case in the oceans of Cambrian Earth, for they are teeming with life.
Deep beneath the waves, an event known as the Cambrian Explosion, has been occurring for the last 20 million years. This event has notably seen an explosion in the diversity of organisms that call our little blue planet home. The seas are notably rich in Oxygen, which feeds this diversity. Most of the organisms of this time are creatures that evolved, in the aftermath of the downfall of the Ediacaran's fauna. Unlike the Ediacaran fauna, however, many of these creatures have relatives that exist to this day and yet they are no less alien to us than the Ediacaran creatures were, as a matter of fact in some ways their even weirder.
Take Hallucigenia sparsa, a strange spiny creature. Hallucigenia is distantly related to modern velvet worms, but you wouldn't know that by looking at them. Hallucigenia notably spend their day crawling along the sea bottom, snatching up food with strange tentacles on their neck and carrying it to their mouths to feed. Also hanging around on the ocean bottom are Wiwaxia, a strange slug-like creature. Wiwaxia, notably spend their day crawling around on the sea bottom, using a single foot, as they forage for food.
The top part of their body is notably covered in spines and scale-like armor. Another creature also in these waters, are trilobites like this Eoredlichia. Trilobites are a notable class of the arthropod phylum. Arthropods are notable for their tough armor like exoskeletons, that they shed frequently while they molt. Arthropods notably stand out for being the dominant phylum at this time, with there being numerous species that take up many different ecological roles.
Some arthropods, notably live more lethal lifestyles and have become some of the first true apex predators. Predation is notably a relatively recent evolution for animal life. Before the Cambrian, most creatures were bottom feeders, or snatched particles through the currents, but now some creatures have begun to actively hunt other organisms. There are many predators in these waters, but one creature rules over them all, meet Innovatiocaris, the top predator of the Chinese seas. Innovatiocaris isn't particularly noteworthy by today's standards, but at 2 feet in length it dwarfs most of the other creatures of this time, most of whom are lucky to get over an inch.
Innovatiocaris is an Arthropod much like the Trilobites, however it is part of a different branch than the Trilobites, for it is part of the Radiodont order. Radiodonts are a diverse order, with many taking up different ecological roles and some like Innovatiocaris have become the first super predators. For the time being, this Innovatiocaris is not hunting, being content to simply patrol its territory, however once hunger strikes it will swiftly search for prey and pretty much anything is on the menu. The prey animals however are far from helpless; they may not be particularly large, but they have evolved defense mechanisms to combat the predators of these seas. Wiwaxia and Hallucigenia have notably developed spines to discourage predation.
Even Trilobites, like Eoredlichia, have a pair of spines behind their heads as well as their tough armored shells to serve as protection. This is arguably the first true evolutionary arms race, for animals and the battle between predator and prey is one that is destined to exist, for millions of years to come. This arms race notably fuels adaptations and it is arguably responsible for just how diverse life is on our planet. Some animals notably do not rely on armor and spines for defense, some rely on other tactics like hiding, often burrowing into the sand, or hiding out in the rocks and crevices throughout the shallow seas. Others, meanwhile, rely on speed.
Take Haikouichthys, it is part of the phylum Chordata. Chordates get their name from a cord that runs along their back and is connected to their brain. The lack of tough armor allows Haikouichthys and creatures like it to be much faster than the armored creatures that also call these seas home. As time goes on chordates will begin to become even more diverse and successful becoming the dominant phylum on Earth, but for now they sit in the shadow of the massive Arthropods that rule the planet at this time. At the moment, these Haikouichthys are searching for food.
Haikouichthys mainly feeds on the small particles that float through the waves, this is due to them lacking jaws, something which greatly restricts their diet much unlike later chordates. As the shoal travels they must be cautious, being at the bottom of the food chain means everything could be a potential threat. Suddenly the shoal is spooked as the Innovatiocaris swims by, despite its threatening appearance however the Innovatiocaris is not actually a threat. This may seem surprising but there is a good reason for this, the Haikouichthys are far too small to provide much sustenance for the giant predator especially with how much faster and more agile they are, plus the Innovatiocaris is still not yet in hunting mode. The shoal quickly relaxes as their panic dies down and they get back to their quest for food.
A few days pass, as life goes on as usual in the shallow sea, we find some Eoredlichia searching for food. Trilobites like Eoredlichia stand out if nothing else for there pure success in the shallow seas of all the Cambrian creatures, they are perhaps the most successful animal group, if one goes my pure numbers and they are destined to last for millions of years to come being a defining family of the Paleozoic era. Despite this however, they are still potential food for the apex predators of these waters. The massive Innovatiocaris has grown hungry in the time since we last saw it and it is quick to take advantage of anything it can get its grasping arms on. One massive advantage Radiodonts like Innovatiocaris have over Trilobites and the other creatures of these waters are their eyes. While Trilobites also have eyes for spotting predators, they are far less developed with far fewer lenses, giving them quite blurry vision, by comparison Innovatiocaris can see about as well as most modern insects.
It quickly begins to swim towards its prey, causing the small group of Eoredlichia to begin scattering like roaches from a light. They however can't move as fast as the Innovatiocaris can swim and soon the massive predator begins to bear down on its target. The Innovatiocaris grabs its prey, however, the Eoredlichia isn't going to go down without a fight, it thrusts its spines right into the grasping appendages of the Innovatiocaris leaving a gash and causing its attacker to drop it to the ocean floor. The Eoredlichia quickly scampers to one of the rocks and with its relatively flat body it is able to hide under the structure. The Innovatiocaris seems almost disappointed as its prey scampers away.
Even the best hunters fail most of their hunts, after all prey animals don't become successful themselves if they can easily be picked off, for now the Innovatiocaris will have to find something else to eat. Meanwhile elsewhere in the ocean we find the shoal of Haikouichthys swimming around, with many of them searching for food. As they search, however, they are being watched from the shadows. While Innovatiocaris may not consider Haikouichthys a sufficient meal, there are other predators who will gladly snatch them up. Meet Nectocaris, a soft bodied hunter of small prey.
Despite its appearance Nectocaris is not actually a squid and yet it is very similar in many ways, this phenomenon is called convergent evolution, which is when unrelated creatures evolve to look similar to one another. Using the element of surprise the Nectocaris charges towards the shoal. The Nectocaris is able to isolate one of the slower individuals and using its tentacles it snatches up its unfortunate victim. Once snagged, the Haikouichthys is doomed; its body isn't built to fight off the larger and stronger Nectocaris. After finishing its meal, the Nectocaris swims off to a different part of the sea.
As it swims, however, it is unaware that it has been spotted by the hungry Innovatiocaris and Nectocaris is a favorite meal of the Radiodont. The Innovatiocaris quickly swims over to its prey and grabs it with its spiny appendages. Once grabbed, there is no escape for the Nectocaris, the Innovatiocaris quickly uses its mouth to eat the struggling Nectocaris alive. After finishing its meal the Innovtatiocaris is content to find a spot to rest its hunger satisfied for now. Elsewhere, we find the Haikouichthys school.
They have calmed down after the Nectocaris attack and they quickly return to their activities. Haikouichthys notably only shoal together for protection and as a result the death of a member is inconsequential and therefore isn't even acknowledged. Soon the shoal begins to swim off, continuing their hunt for food. As the Cambrian ticks on, life will only continue to diversify as new and even stranger creatures continue to evolve. The chordates will be among these creatures as they continue to evolve into new and more advanced forms.
We are now in what is now British Columbia, 508 million years ago. At the base of any underwater cliff, we find a landscape teeming with perhaps even more life than China 10 million years before. Sponges and Brachiopods notably sit stationary against rocks and other structures. They notably suck in water and filter through it snagging small organisms whenever they can. There are many other creatures that also call these waters home.
Take these small creatures swimming through the water known as Marella. Marella stand out for being the most common animal in the region. They notably rely on their spines for protection against predators. There is also Waptia, another common creature in these waters. They mainly rely on their speed to escape predation.
Of course they themselves are predators hungrily snagging small animals that can't escape their grasping arms. Life on the ocean bottom is notably just as numerous. Hallucigenia and Wiwaxia are some of these creatures, they have persisted mostly unchanged for the last 10 million years and are as successful as ever. Trilobites, meanwhile, are as successful as ever with the genus, Olenoides, being one of the most common in these waters. Meanwhile beneath the sand we can find many types of worms like Ottoia.
Ottoia are burrowing animals that hide under the sand of the sea floor waiting for anything unlucky enough to wander by. Of course they themselves are potential prey for other creatures. Take the five eyed Opabinia, known by some as the strangest creature to have ever lived. Opabinia, is if nothing else absolutely bizarre. Notably the strange creature is equipped with a proboscis that it uses to grab food too pull into its mouth.
It also has legs allowing it to talk on the ocean bottom and yet it can also swim much like a radiodont. This particular individual is using its proboscis to sift through the sand as it hunts for food. This Ottoia has no escape. The Opabinia quickly grabs ahold of the worm and begins to feed. Elsewhere we see a different drama unfolding.
Meet Pikaia, a strange creature that almost looks like a worm, yet it is actually a chordate like the earlier Haikouichthys. Pikaia notably leads a very different life compared to Haikouichthys. Notably they are less social, only gathering together to breed and sometimes if there is a lot of food. Pikaia notably feeds on similar food to Haikouichthys, however this is about the only outward trait that seems to be shared between the 2 and yet they are actually close relatives, a true example of how different even early Chordates can be. Elsewhere we find some Hallucigenia foraging in the sand, using their strange tentacles on their necks to grab food, however, unknown to them they are being watched.
Swimming in from above, is Anomalocaris canadensis the apex predator of this region and a close relative of the earlier Innovatiocaris. Anomalocaris is notably just as big as its earlier cousin. The Anomalocaris moves in, causing the Hallucigenia to instinctively curl up. The Anomalocaris prods at its prey knocking it around and yet it can't find a way around the spines. Realizing the spiky Hallucigenia simply isn't worth the effort, the Anomalocaris swims off.
With the threat gone the Hallucigenia uncurls itself and continues about its day. Survival for predatory animals is notably just as difficult as it is for prey animals. Notably while Anomalocaris is a force to be reckoned with, its large size means it has to eat a lot of food. This is of course problematic when everything seems to be perfectly equipped to deal with you. Luckily for this male he is nothing if not persistent and he hasn't grown this large by being a failure he will strike again and it is quite likely his next target won't be so lucky.
Meanwhile, we find the Pikaia swimming through rocks. A small group has come together by chance to take advantage of a bunch of food particles in the area. Nearby watching the group intently is the Opabinia and it has once again grown hungry. Catching Pikaia is quite difficult however they are quite fast creatures and they are also very agile, more than capable of outmaneuvering the more sluggish Opabinia. To catch one, the Opabinia must use the element of surprise.
Carefully the hungry carnivore moves closer and closer to its targets attempting to single one out. The Pikaia, are notably none the wiser to its presence. Finally the Opabinia burst out from hiding causing the group to scatter, unfortunately for the predator it strikes too early. The group has long since scattered leaving the Opabinia without a meal. The Opabinia simply has to accept its failure and try again some other time.
A little bit later we find a Waptia with another of its kind in its claws. Cannibalism is a common practice in the animal kingdom and Waptia is no exception. This Waptia however, did not make this kill for itself. Hiding nearby in some rocks are young Waptia; this particular Waptia is a female and a mother for that matter. While most creatures at this time leave their young to survive all on their own, some creatures like Waptia actually take care of their young.
Waptia notably have fewer young than most creatures, but by watching them they insure the survival of their young more efficiently than other animals. In time many other creatures will adopt a similar mode of parental care. The mother lets the young feed on her catch. The fact that this is a member of their own species doesn't phase the young after all in a harsh world like this one has no time to wonder about morals. Survival needless to say is the name of the game.
After the kill is finished the young head back to hide in the rock, their mother close behind them. They won't have their mother forever and if they don't leave after they reach a certain size the mother will likely kill and eat them with no hesitation. For now however, life continues on as normal for these bizarre creatures. Further away from the rocks, we find ourselves with the Olenoides. One of the Olenoides has notably stopped to molt.
Molting occurs when Arthropods get too big for their current exoskeleton causing them to shed it. The process itself is a long and arduous one for the little Trilobite. After a few long minutes, the Olenoides finally breaks free from its old exoskeleton. The new exoskeleton is notably rather soft and brittle and it can take a little while for it to harden. This is not good for the Olenoides and it leaves it vulnerable to predation.
Swimming in from above, is the Anomalocaris. The predator quickly swims towards its prey, snatching it up quickly. Normally the armored shell of Olenoides would provide protection, but the unfortunate Trilobite has no real defense. A sickening crunch rings throughout the water as blood flows. The Anomalocaris quickly devours its prey.
The Olenoides will feed the Anomalocaris for a few days at least. The Anomalocaris satisfied swims off leaving only a few scattered pieces left. Other Olenoides are quick to take advantage. Being scavengers they will happily eat whatever is left on the sea bottom. As the days continue to tick on, life continues quite peacefully for a time.
We find our Pikaia once again searching for food, however, this time they have wandered out into the open. This mistake could prove fatal. Watching nearby, is the Opabinia once again it is hunting the Pikaia. The predator moves in slowly, watching its prey intently. The Opabinia is slow and methodical as it moves closer to its target.
Finally the Opabinia strikes, swimming quickly towards its prey. The Pikaia, fail to notice the predator until it's too late. The Opabinia grabs one of the Pikaia with its proboscis. Afterwards the predator pulls its prey towards its mouth and begins to feed. Satisfied, the Opabinia begins to look for a place to rest.
Unfortunately for the Opabinia, its search is about to be cut short. Suddenly the Opabinia disappears in a flash, as an Anomalocaris snatches it up. This Anomalocaris is not the same one we have been following, however, it is a rogue male. Anomalocaris are very territorial creatures and as a result the rogue's presence is unlikely to be tolerated, after all there can be only one giant predator in an area. Anomalocaris notably have to claim territories for their own by taking them from other members of the same species; afterwards they must routinely fight off rivals to keep said territory.
A confrontation is likely to occur soon. About a day later we find the resident male Anomalocaris patrolling his turf. It seems that he has yet to find the rogue, however, that is about to change. Emerging from the water ahead of him is the rogue. The encounter immediately begins to escalate.
The two males size each other up circling as they do so. Confrontations will often end here, after all big predators can't afford to get grievously injured as it will impair their hunting ability. As the two circle it seems that they are quite similar in size. In situations like this the conflict often escalates to a physical one. The rogue male makes the first move and headbutts the resident male.
The blow, if nothing else gets the resident males undivided attention. The resident male quickly retaliates, swiping his rival across the face with his grasping appendages. He then headbutts the rogue right in his mid section. The rogue quickly recovers from the blow and the pair begin circling again. The resident male is notably older and more experienced, however, he lacks the youth and endurance of his rival, a weakness which could come to bite him should the battle wage for too long.
The resident male goes for a move that should end the fight if it works. He quickly maneuvers behind the rogue and latches on from behind forcing his adversary to carry his weight. He then begins to pull up on the head of the rogue, the goal being to crack his armored exoskeleton. Unfortunately for the resident male, the rogue is stronger than he is, his age has begun to betray him. The rogue is able to fight the maneuver and he begins to find his way out of the resident male's grasp.
He finally pulls his head free, breaking the resident male's grip. He then swims around his rival. The old males has notably, expended a significant amount of energy while trying to finish the fight and this has left him vulnerable. He is unable to react fast enough in his tired state to stop the rogue male from latching on to him in the same way. The rogue quickly begins trying to split the armor of the resident male.
Once again the resident male's age betrays him as he struggles to fight his rivals grip. The rogue quickly pulls on his head, as a sickening crunch rings out through the waves the resident male's armor has cracked. Quickly he swims off in the span of a few short minutes he has lost everything. The rogue male meanwhile, relaxes for a moment while he may be young, the fight has nonetheless left him a little winded. Finally, he begins to swim off and explore his new territory.
The old male meanwhile swims away from the area he once ruled. Survival will be tough for him, his armor is cracked and his age means it will be hard to recover from his injuries. He begins to swim off, into the unknown. A month later we find ourselves at the bottom of the underwater cliff that lies above the lush patch of sea below. We find an interesting sight, at the bottom of said cliff.
The old male lies lifeless at the bottom; he was unable to survive his injuries usually his body would become food for scavengers. However this will not be his fate. Suddenly a section of the cliff collapses and buries his body alongside whatever is unable to escape in time. As the dust clears, calm returns to the sea once again. This is the fate of many creatures both alive and dead.
Events like these, will notably be responsible for the excellent preservation of the creatures that call these seas home and in 508 million years time many will be dug up by paleontologists and provide a window into a past that is unlike any other. For now at least however these creatures will lay buried beneath the sea, a brutal grave of those who have passed on. Elsewhere we find the male Anomalocaris patrolling his new turf. While his violent takeover may seem harsh it is necessary for the survival of his species. Notably males like him will continue to provide new blood for his species allowing them to continue their success.
The Cambrian is a truly monumental time in the history of life, with many strange and unique creatures becoming dominant. This period won't last forever however. About 485 million years ago, the Cambrian will begin to come to an end with an extinction event. Many of the strange life forms won't survive and those that do will be forced to adapt to a changing world. This however will breed new creatures whom quickly will begin to adapt as the Cambrian ends and the Ordovician begins life will continue to diversify and many of the families that reign in our time will begin to appear.
The next chapter in Earth's long history is set to unfold.
Trivia
This episode's segments are based off of the Moatianshan and Burgess Shales respectively; these fossil groups notably, provide a clear window into life during the Cambrian and are easily the best representatives of the Cambrian Explosion and its impact on life.
I considered early on setting this episode's 2nd segment, in the Emu Bay Shale, however, I ultimately decided against this as the Emu Bay is notably nowhere near as rich as the Burgess Shale, on top of this it lacks any known Chordates to my knowledge and I am overall happy with my decision to ax this idea.
I had some trouble getting good size estimates for Anomalocaris and Innovatiocaris, especially since sources seem to disagree with each other (What else is new) on top of this, the Innovatiocaris specimen is said to be a juvenile , making it even harder to get accurate sizes. I ultimately went with 2 feet as this size seems reasonable enough.
For the record, I am aware of the new paper on Anomalocaris diet. I personally wasn't convinced by the paper myself and I found it rather flawed for reasons I won't get into here. Ultimately I find it most likely that Anomalocaris and Inniovatiocaris were generalist apex predators that ate whatever they could. That's just me of course, feel free to disagree.
I originally was going to include scenes about sexual dimorphism in Hallucigenia and Ontogeny in Wiwaxia respectively, however, I was unable to find a good spot to put them, so I made the unfortunate decision to ax them.
Originally I was going to have the Anomalocaris hunt some Marella, but I found the scene superfluous and I axed this idea as well.
The Anomalocaris fight as you can likely guess is a shoutout to WWM
That's all for this chapter. In the next one we will travel to the Ordovician stay tuned…