Paja Formation, Colombia, 118 Million Years ago

The mid-day sun casts a steady light across the sky, illuminating the upper west coast of South America. In our modern day, this land will be where the Colombian Andes would grow and further bleed into other parts of the continent. Even parts of the Amazon Rainforest would be eclipsed by this same mountain range.

However, such mountains have yet to form. Instead, higher sea levels have resulted in much of Colombia being flooded, turning even the central parts of the country into a coastal environment. Small parts of the westernmost sections of the country remain as dry land, but are separated into islands. Although the land bridge between North and South America is still present, it's in a different position than it is today.

Steady waves continuously splash and recede on the white sands of the Colombian shore. This beach acts as a border between the ocean blue and the humid forests on the land. Much of it is made up of ancient Conifer trees, towering over a bed of ferns and cycads.

Bits of these plants are also scattered across the seaside, having been blown away by storms of the past. Some lay hidden by the sand, occasionally sticking out along with the various seashells and bones of dead animals. The rest is carried away by the tide, drifting it out to sea.

The movement of the waves also reveals the many rocks that line the shallows and even rest at the shoreline. Many of them are merely small pebbles towered over by the occasional larger stone. More minuscule ones are often smooth and rounded while the much bigger ones are pointed and jagged. They are also home to barnacles and algae, the white shells and green slime standing out against the black craigs they cling onto.

Other ones are seen much farther away from many of the other sea stones, only surrounded by the white sands submerged by the ocean current. Curiously, some of these rock shapes are slowly moving. Inch by inch, they gently grow closer to dry land.

However, moving past the receding tide reveals much more to these perceived rocks. Limbs swing upward, repeatedly dragging them across the sand. Heads at the front poke up, letting out a deep gasping noise as it inhales air amidst the crash and splashes of the tides they emerge from.

These are not rocks but merely Desmatochelys, the earliest sea turtles. Water-dwelling terrapins have been around even before these evolved. It's only now in the Early Cretaceous that these shelled animals are taking the form we recognize in our modern day. Despite this, their relatives that permeate today's oceans are directly descended from these ancient reptiles.

Unlike what's seen in most sea turtles, Desmatochelys have a thick, leathery shell akin to that of the modern leatherback. These carapaces covering their 6-foot-long bodies are flexible yet tough, with a surface that is slightly ridged. Four large, paddle-shaped flippers stick out from these shells, adapted for swimming yet also effective in dragging the turtles across land. Short tails stick out from the back but are hidden by the turtles' carapace. Protruding from the front of the shells are sleek, slightly elongated heads with pointed snouts. These heads end in sharp, strong beaks built for grasping and tearing soft prey. The rubbery skin of these turtles is primarily charcoal gray with faint, irregular deep, blue spots covering it and the shell. This coloration is only interrupted by the occasional small barnacles that have latched themselves to many parts of the turtles.

From the foaming tides, the Desmatochelys emerge onto the sandy Colombian shores. Such actions are a grueling effort for animals adapted for life in the ocean. On land, they feel every ounce of their massive weight fastening them to the earth. Even their massive flippers can only carry them across shifting sands in short, repeated bursts.

Despite such difficulties, many Desmatochelys haul themselves onto the shore. What initially appears as a handful quickly turns into the 10s before building up to hundreds. Each one gasps for air as they shift the sands beneath them.

Only one event can bring these ocean-faring turtles onto dry land. With the arrival of summer also comes the nesting season. Unlike the many other marine reptiles they share the Cretaceous ocean with, Desmatochelys don't reproduce via live birth. Rather, they still retain the ability to hatch from eggs. Since these structures require oxygen, they must be laid on land. Additionally, the eggs will be out of reach of their oceanic predators. Such a strategy has proven so successful that it will even be seen in sea turtles millions of years after the extinction of Desmatochelys.

As the first of the turtles arrive at the top of the beach, it slows to a stop. Next, this first female begins to utilize both her back and front flippers to spread away tufts of sand. These hind limbs may not be as long as her front ones, but they're well-suited for digging into the beach.

Soon, more of the approaching females arrive on the high ends of the beach and start boring into the sand. The border between the coast and the mainland forest quickly becomes packed with burrowing turtles. These Desmatochelys clustering together makes it a challenge for lagging females to find their own spots amidst it all. Some are deterred by turtles who've already started nesting, sand from their digging kicked into the faces of their rivals.

The constant plowing into the beach creates a pit around each of the turtles in addition to a large, 3-foot-deep hole beneath them. This prompts them to finally release their precious cargo. They do so through a fleshy tube below their tail that gently drops each egg into the deep hole. Each egg is fragile and thus needs to descend slowly through its mother's tube to avoid breaking. Since each female will end up laying over a hundred golf ball-sized eggs, depositing them all can take upwards of an hour.

After much time, the first females to arrive manage to lay the last of their eggs. With this out of the way, the turtles again utilize their flippers. This time, they don't dig the beach but rather put sand over the nest holes.

Laying eggs on the shore will have many benefits to the unborn young. First, they'll be hidden from any predators that might pass by in the future. Second, the eggshells will be able to remain moist as opposed to drying out in the hot sun. Third, is temperature control, something deeply vital to the development of the turtles. Not only do they need to be kept properly warm to hatch, but the heat distributed to the eggs will also determine the sex of each young turtle. Warmer temperatures will hatch females, while cooler ones will hatch males. Thus, it will be important to maintain the perfect middle ground to ensure an evenly distributed amount of the two sexes upon hatching.

Undoubtedly the most important part of the turtle's nest is its location. The eggs may remain hidden from predators until hatching, but they're still vulnerable to weather and even the ocean's current. If the nests are made anywhere lower than where the high tide peaks, the eggs will be easily washed out to sea.

With the nest building finished, the Desmatochelys start to leave for the water. As is the case with modern sea turtles, these mothers won't meet any of their offspring. When the babies hatch 60 days from now, they will have to face the challenges of their new world alone. For some of these females, it may not even be the first clutch of eggs that they'll lay during the breeding season.

However, some may not make it past this one beach. In the waters beyond the shore, a pair of massive jaws breaches the surface. They clamp on one of the Desmatochelys before hauling it down. In the blink of an eye, both predator and prey disappear. This is a world where the lives of sea turtles are not guaranteed, even as adults.

***

Two months have passed since Desmatochelys first dragged themselves onto the shores of ancient Colombia. Little has changed despite such time, but now night, many of the beach's features are encapsulated in darkness. The only source of light is the faint, orange sun emerging from the horizon. Its shine shimmers across the ocean surface, creating a dazzling display.

On the beach, everything's quiet, the only noise coming from the tide's rhythmically soaking of the sand. Amidst this, movement starts to occur, not from any visible animal, but from the beach itself.

Grains of sand shift as they start to cave inward. Then, a small, dark shape is put out of the sand. In this shape, two pairs of grain-covered eyelids open up, witnessing the above-ground world for the first time. Long, flipper-like limbs poke out before pulling its shelled body out of the sand.

At long last, the Desmatochelys eggs have started to hatch. This 3-inch-long newborn is different from its adult counterparts. Its head is proportionately larger, particularly in its eyes, giving it an alert and innocent expression. This skin coating is much darker, matching the night sky's darkness. The tail is so small that the slightly protruding nub is almost imperceptible. Most dangerously, its shell is much softer than those of the adults, making it much more vulnerable to the dangers that lie in wait.

Thus, the turtle wastes no time in scrambling across the shore. Although it moves quite slowly across the sand, it's not bound by the weight of its mother before it. This allows it to more effortlessly lift its body as it traverses the beach.

Immediately, more hatchlings start to poke through, following their sibling in its footsteps. What started as a small hole for a single baby turtle to leave quickly becomes encapsulated by a swarm of shells with flapping flippers. Each one scrambles in a different direction from the other, lost in where it must go.

Before long, their general direction starts to shift. An intuitive few spot the sparkling waters of the sea. They may not have been on this earth for long, but instinct tells them this is where they must go. As they set their course, their many siblings begin to follow.

As they roam the soft sands, the baby Desmatochelys spot hundreds of their kind. This number instantly grows to the thousands as more of the little turtles rise from the earth. Their appearance is generally the same, but there are at least a handful of exceptions.

On rare occasions, a Desmatochelys could be born with a change in their physical shape. One little male has emerged with one front flipper shorter than the other. The difference is minor, but it has already made moving across harder for him as opposed to his peers.

He's also one of the first to be taken by one of the predators that lie in wait. From a hole in the sand, a crab springs out, grabbing its crushing claw onto the young Desmatochelys. The newborn frantically flutters his flippers, but it doesn't stop the crab from pulling him under the sand. The crab may be no bigger than the little turtle, but it will be able to make a long-lasting meal out of him.

If Desmatochelys do have mutations, few are fortunate to have ones that don't hinder their chances of survival. Some experience changes that only affect skin color. One emerging turtle, Camila, has a spot of white on the skin around her eye, making her easily identifiable amongst the amassing army of hatchlings.

Like the other newborns, the female trudges across the beach toward the reflective waters of the sea. As she does, more of the turtles progressively become snatched up by wandering crabs. Neither she nor her siblings are capable of fighting them off, so her only hope is to outrun them.

Unfortunately, another threat to the turtles' lives makes their presence known. It does not come from below but from above. Swift shadows zoom over the hatchlings before large flyers crash onto the sand around them.

These are Maaradactylus, South American members of the pterosaur family of flying reptiles. Their name is inspired by the Carriri legend of a woman who was turned into a river monster that devoured a fisherman. Normally, they'd be much more common in Brazil, but won't pass up a feeding opportunity in a nearby country.

Much like the folklore monster with which they share their name, their long, narrow heads have jaws lined with long, conical teeth. The ends of their snouts end in a half-oval-shaped crest on the top and bottom. In the females, these structures are colored in a dull gray to match the skin on the rest of their mouths. For the males, these crests are a bright blue with a solid white spot in the center. The rest of their bodies are none too dissimilar to those of many other pterosaurs, including their membranous wings that stretch up to 20 feet in length. Much of their forms, except for their snouts, are covered in dull black pycnofibers. In the wings, the same dull gray seen in their snouts is faintly visible under their integument.

Nearly a dozen Maaradactylus have gathered here, swooping down onto the shore below. Each one swiftly snatches their needly jaws onto a helpless turtle before swallowing it whole. As the pterosaurs crawl around onto the sand, the young Desmatochelys are powerless to escape once caught. Like with the crabs, all they can do is keep moving.

Amidst the chaos, another obstacle arrives at the beach. Its presence is signaled by thundering thuds felt by all that touches the ground. Deep, breathy rumbling and creaking groans also echo throughout the coast. These sounds and vibrations grow stronger as the shadow of something massive engulfs the turtles and the Maaradactylus. The pterosaurs fly backward to avoid the feet of titans.

Camila peers up to find their largest hurdle yet, a passing herd of seven Padillasaurus. These are 60-foot-long, Colombian members of the famous sauropod clade of long-necked, herbivorous dinosaurs. Their massive, robust, 11-ton bodies have deep, barrel-shaped chests. Four, pillar-like legs stand erected beneath them, supporting their immense weight as they trudge along. Long, tapering tails help to balance their enormous forms. Perched atop their long, graceful necks are relatively small, boxy heads with a somewhat rectangular shape and a rounded snout. Inside their mouths is an array of peg-like teeth. Their skin is a mosaic of greenish-gray scales except for their smoother, light gray underbellies.

Like all sauropods, Padillasaurus are herbivores and therefore won't be interested in eating Camila and the other Desmatochelys. However, their traveling proves to be yet another danger to the lives of the young turtles. The immense weight of their feet alone is enough to flatten anything unfortunate enough to be under them. Thus, even a single step can prove fatal for a baby turtle.

Even as Camila pauses in awe of the giants, hatchlings around her become squashed attempting to navigate around their feet. The flattened turtles also attract the Maaradactylus, seeing them as an even easier meal. With the flyers distracted, the remaining newborns continue on their route to the sea.

However, Camila's approach is brought to an abrupt stop. One of the Maaradactylus has caught her in its jaws. She ends up slipping a few times only for the pterosaur to quickly regain its grip. It begins to raise its head, ready to ingest the helpless turtle.

Suddenly, one of the legs of a Padillasaurus hits the Maaradactylus in the head, causing it to tumble over. In the process, Camila is also sent flying briefly before landing in the sand. She manages to flip her body back up only to find her hunter wiggling around as it regains consciousness. It opens its eyes only to let out a deep honk as another sauropod foot lowers toward it. With a thunderous smash, it lands on the pterosaur, causing its wings to fling upward before lifelessly dropping.

At last, Camila's immediate pursuer is dealt with. Despite this, she doesn't stay for long. After so much chaos and trudging across the sand, she and a few of the other turtles leave the shore.

Massive waves carry them into the dark blue waters. The movement of their flippers transforms from crawling into swimming. Any sound from above is muted by the bubbling and rushing of the underwater world they've entered.

The sand they left from dry land follows them on the bottom of the shallows. Rocks start to appear as well, yet are more frequent than seen on the shores. Algal plants are present as well, mixed in with bits of vibrantly colored coral and seashells. The distance is masked by an expanse of darkness.

Out of the thousands of Desmatochelys that have hatched on the beach, Camila is one of only a third that has made it into the water. With the amount of dangers they have to face, few can survive. Their only strength in making it this far is in their numbers. The more turtles there are at once, the better the chances are that some will survive.

While the newborns may finally be in the water, their troubles are far from over. As they further transition from the shallows into the open sea, a whole new set of underwater predators appears.

The first of them are ammonites, ancient, shelled cephalopods. Their appearance is much like squid and octopus with the texture of their skin and the floating tentacles surrounding a sharp, beaked mouth. The main difference that sets them apart from their more recognizable relatives is the large, snail-like shells that house their bodies.

Using their tentacles, they quickly grasp at the young Desmatochelys before pulling them toward their mouths. Their beaks easily crush their prey's shells, making them easier to digest.

Soon, another kind of oceanic predator joins the feast. It's an early ancestor of a type of hunter that will prowl the oceans of our modern day. One part of an ancient lineage of carnivores that dates back long before even the dinosaurs: sharks.

These are Protolamnas, the earliest known mackerel sharks. As such, their extant relatives include the likes of makos, sand tigers, and even the great white. Their bodies are torpedo-like with tiny, rough scales to reduce drag, allowing them to swiftly and effortlessly glide through the water. Fins grow from these bodies, including two triangular pectoral fins, two tail fins that form a crescent shape, and one recognizable dorsal fin. The heads are somewhat elongated and streamlined, tapering to a pointed snout. Large, sharp eyes positioned on the sides give them excellent peripheral vision with which to spot prey. Slightly curved, triangular teeth line their powerful jaws, making them great for gripping and tearing into the flesh of their prey. Their skin is primarily bluish-gray with a solid white underbelly.

With how small the baby Desmatochelys are, the sharks need not even bite them. Rather, they swallow them whole as they dart through the group of swimming hatchlings. Often, more than one is caught at once due to how big the mouths of the sharks are compared to the little turtles.

Many predators roam these waters, ones that are more than willing to snack on the newly arrived turtles. One final kind joins the fray, one unseen in the waters of our modern day. The tiny newborns are far from safe, even from other reptiles.

Darting around the turtles at blinding speed is a small pod of Muiscasaurus. They are late-surviving, South American members of the ichthyosaur order of fish-like marine reptiles. This group was once much more common throughout the Triassic and Jurassic, but is now decreasing in numbers and diversity as the Cretaceous continues.

Their sleek, hydrodynamic, 15-foot-long bodies are slightly expanded by a layer of blubber under their skin. Four paddle-like flippers grow from their pectoral and pelvic regions. Fins are present as well, including a tall, slightly curved dorsal fin on their backs and two caudal fins that form a semi-circular shape at the end of their tails. The heads are long and tapered with a streamlined shape, narrow snout, and a mouth full of sharp, conical teeth. Large eyes positioned on the sides of these heads allow them to effectively spot prey even in dark conditions. Their smooth, scaleless skin is primarily white with black on their heads, fins, and the ends of their tails.

At astounding speeds, the Muiscasaurus zooms around the army of turtles, biting onto one before swallowing it whole. They'll also occasionally come into conflict with the sharks, gnashing their teeth at one another, to get them to back off.

With how many predators there are and no way to fend them off, all the Desmatochelys can do is keep swimming. As they do, attacks from carnivores begin to disappear. One by one, each of their pursuers begins to swim away from the little turtles, fading into the distant dark blue.

Finally, the surviving hatchlings have crossed the threshold into the open ocean. Though they only do so at a high cost. Out of the thousands that hatched on the beach, only a few hundred remain. However, it was their numbers that helped them reach this far. Many predators on the Colombian coast would make an easy meal out of the newborn turtles, but even these are exceeded by the many turtles that hatch at a time. Eventually, their hunters will give up simply from a full stomach, granting the few that do make it through the onslaught a greater chance at making it to adulthood. Even then, such survival is far from guaranteed.

***

15 years have passed since Camila was born on the shores of Colombia. In that time, little has changed in the overall environment. The only difference between now and then is that it's daytime. With this time of day comes a greater amount of sunlight illuminating the seafloor. Everything from the rocks to the coral, the sea anemones, and the other underwater residents of the shallows are bathed in shining waves.

Amidst this glimmer, shadows gently float across them too. They appear almost oval-shaped with four large flipper appendages growing from them. One need only look up to find the source of these silhouettes: female Desmatochelys.

Among the traveling turtles is Camila, no longer the helpless hatchling that emerged from her nest all those years ago. Now, she has attained her full adult size and a much stronger shell. This has provided her defense from the predators that terrorized her in her youth. Animals like ammonites, Muiscasaurus, and even the Protolamna sharks simply pass her by, focusing their attention on much smaller prey.

This is the first time Camila has been in these waters since she hatched. Like modern sea turtles, the instincts of females always drive them back to the same beach from whence they were born. Today, it will be for the same purpose as their mothers before them, to lay their eggs. The journey spanned miles from their regular feeding grounds, thus exhausting them. Camila especially feels this tiredness as she flaps her flippers less and less, instead letting the tide guide her through the shallows to shore.

Unfortunately, now is not the time for such fatigue. Even as adults, the Desmatochelys aren't immune from the dangers of the ocean. As Camila and the other turtles drift to the edge drop-off point of the shallows, a large animal emerges from the dark blue behind them.

This is a massive, oceanic predator, known only as Monquirasaurus. It is a type of pliosaur, a plesiosaur with a short neck but an enormous head as opposed to the popular inverse of the larger order. At 33 feet in length, it's easily one of the largest in this predatory family.

Much like other members of the pliosaur family, its head is proportionately immense, making up nearly a quarter of its total body length. This broad, powerfully built skull sports long, robust jaws, lined with conical teeth that interlock when the mouth is closed. Its muscular body is somewhat streamlined with a noticeable bulk around the midsection. Four large flippers produce powerful strokes that move it through the water. A relatively short, thick tail grows out from its rear. Its smooth skin is a shadowy gray with scattered spots of solid white and an underbelly of the same color.

This is the biggest threat Camila has ever faced. With such strong jaw muscles, the Monquirasaurus can make an easy meal out of an otherwise near-invincible Desmatochelys. And with how exhausted each of the females are from their voyage, they have become much easier, slow-moving targets. Their only hope now is to keep swimming to the drop-off point at the shallows. There, the predator will be too large to follow without the risk of being beached.

With all the strength they can muster, Camila and the rest of the Desmatochelys speed up their swim. Even without such exhaustion, the turtles can only manage a speed of 15 or so miles per hour. The Monquirasaurus, however, easily closes in, matching the speed of a modern dolphin. Only less than a foot away, Camila pushes on past a much slower turtle. The sluggish Desmatochelys is immediately trapped in the jaws of the Monquirasaurus. It's helpless to escape as it's thrashed above the surface before being taken into the distance.

Finally, Camila's journey through the familiar waters draws to an end. She gently floats through the shallows, allowing the waves to carry her to the edge of the beach. Her arrival is welcomed by the fresh, seaside air which she inhales with a loud huff.

For the first time in fifteen years, Camila drags her body across the beach sand. Now that she's much larger and heavier than when she hatched, terrestrial travel has become a much harder challenge for her. Her exhaustion from such a long journey doesn't help her much either. Nonetheless, she presses on, along with the myriads of other turtles that haul themselves onto shore.

As her mother did long before her, Camila eventually reaches the point of high tide. Then, she carves a pit into the sand around her with an additional, smaller one below her rear. Finally, she deposits her cargo of eggs before concealing them on the beach. Now, she's free to leave the shore and return to the ocean blue.

The lives of sea turtles such as Desmatochelys are among the most challenging of any animal in the natural world. Even in the modern day, only one out of every thousand of these creatures will ever make it to adulthood. Thankfully, with enough drive and numbers, their lineage will be successful long after the extinction of Desmatochelys. Every subsequent generation will be one whose destiny will be carried by the current.