Hosselkus Limestone, California, 226 million years ago

In the western regions of the United States lies the Sierra Nevada. This landscape is dominated by rugged limestone cliffs, stretching over 400 miles long. Beneath these jagged peaks, pine forests and vast lakes like Tahoe create one of North America's most serene environments. Although this mountain range doesn't reach as far as the Appalachian or Rocky Mountains, its tallest summit, Mount Whitney, towers above all others in the continent at over 14,500 feet high.

In the Late Triassic, this great Californian mountain range lies submerged at the bottom of moderately deep waters. Above where the summits would hit their peak, fading daylight shines off of gentle waves. This change also means that the great lakes and conifer forests of Yosemite are absent as well.

At this time in Earth's history, the continents as we know them are still conjoined in a single landmass. This arrangement birthed a massive superocean, nearly spanning the entire globe. Just as Pangea is "all land," Panthalassa aptly means "all sea."

As it tends to be this far from land, the ocean waters are fairly quiet. Sea birds have yet to evolve, so their familiar calls are absent. All there is for sound is a soft breeze and the smooth flow of waves.

Below the surface is where it appears most vacant. Where bits of land can be seen fading into the horizon above, what lies in the underwater distance is shrouded by dark blue. It's closer to the surface where the area is most visible, the light above making the waters appear a clearer azure as it peers through. With night approaching, this clarity is slowly being consumed by the encroaching darkness of the deeper depths.

With land being distant, these high seas are largely barren, the ocean equivalent of a desert. Despite this, marine life does thrive here in abundance. The most common just so happens to be its smallest.

As is the case in our modern oceans, plankton can be found in nearly every part of this ancient marine world. They're incredibly small to the human eye, appearing only as tiny particles without the aid of a microscope. Unable to actively propel themselves, they instead drift wherever the current takes them. To nourish themselves, they rely on a technique known as photosynthesis, wherein they absorb sunlight and convert it into nutrients. This same method is used by plants, just added with the soaking up of water.

Naturally, they gravitate closer to the sunlit surface where the light is most abundant, leaving the deeper water behind. In doing so, they kickstart a vital feeding chain for the ocean's residents. It all starts with a familiar type of marine life.

Fish, the oldest groups of backboned animals, having been fully aquatic since the dawn of life on Earth. In this long time, they've evolved and diversified into several forms well into our modern day. Some, like these anchovy-sized species, have developed the ability to filter-feed, using specialized gills to strain plankton from the water. This feasting benefits both the fish and the ecosystem, preventing the buildup of these microorganisms from triggering toxic algal blooms.

In their feast, the fish gather in the millions, forming dense, shimmering clouds that swirl and shift in perfect sync. Out in the sea, however, these filter-feeders are themselves food. Another species hunts them in mass, slicing through the water to snatch mouthfuls of their plentiful prey. The liquid blue comes alive with its bubbling rushes and splashes as they spring through the surface.

These hunters' roots lie not in the ocean, but on land. Called Californosaurus, they belong to the ichthyosaur order of marine reptiles. As with many of their relatives, their 10-foot-long bodies are sleek and streamlined like dolphins. They even have a layer of blubber underneath their smooth skin. Four flippers grow from these bodies, the front half being nearly double the length of the rear ones. They also have a single dorsal fin and two caudal fins that form a crescent-like shape. Large expressive eyes rest in front of long, narrow snouts filled with sharp, conical teeth. Across the midsection of their bodies, their smooth scaleless skin is a deep, slate-gray with a solid white underbelly. Meanwhile, the skin on their limbs, snouts, and around their eyes is a dark gray.

As dolphins and porpoises do in our modern day, ichthyosaurs like Californosaurus are perfectly adept at feasting on these fish. With how fast they're able to dart through the water, they easily catch up to their prey. Even so, the shoal remains alert, circulating in unison to avoid the missile-like approach of their predators.

But Californosaurus aren't the only ichthyosaurs here to feed. Another member of this astounding group lurks from the dark blue beneath the fish tornado. Suddenly, it rises, drastically dwarfing the pod of Californosaurus. It jolts through the prey cloud, gulping many fish within its mouth. While it feeds, the animal's body pierces through the veil of the surface, creating a loud splash as it exits the water. Only the front half of this massive animal pokes through, liquid already running off its body like several mini waterfalls. Upon returning to the sea, its body hits with the power of a cannon, creating a giant explosion of white. Below the surface, hundreds of bubbles trickle around the animal's body, gently disappearing to reveal its massive form.

This is Ava, a female Shonisaurus. Reaching 50 feet in length and weighing nearly 30 tons, she's nearly the size of a modern gray whale. Even the biggest of the Californosaurus almost look like minnows in comparison to this ocean titan. She, too, is a type of ichthyosaur, but she belongs to a different family within this order known as the shastasaurids. Other species within this family have been found across the northern hemisphere from North America to Asia and even parts of Europe. Only a few will exceed her species in size, even rivaling the modern blue whale.

While she still retains a similar, streamlined form as other ichthyosaurs like Californosaurus, she also appears tubbier with a more oval-shaped body. Four long, narrow flippers grow from her body, aiding in steering. A lengthy slender tail helps propel her through the liquid azure, having an end that's comparable to a thresher shark's but upside-down. A small, triangular dorsal fin rests on the middle of her back, appearing like that of many modern whales. Large, dark eyes rest on a narrow, elongated head with a mouth lined with sharp, robust, conical teeth. The smooth skin of this titan is mostly a dark, rich charcoal gray, gradually softening into a paler grayish-blue underbelly along with white lining the edges of her mouth. Often, this coloration is interrupted with thin, white scars and the yellowish-pink of lice-like crustaceans latched to various parts of her body. Skin worms are another parasite present, their snake-like outline faintly visible under her hide.

With such an astounding size, the smaller animals around Ava give her a wide berth, even the Californosaurus. The fish especially are frightened of her mere presence, scattering in many directions before recombining into another swirl.

But like Californosaurus, Shonisaurus don't travel alone. From the depths below Ava, more of her kind emerge, consuming any amount of fish they can come across. Her pod is over 10 strong, primarily being adult females like herself, but also sub-adult calves. Regularly, the Shonisaurus fill the waters with low rumbles and hums as their methods of communication.

Among the youngsters is Ava's own son, Carlos. Like his mother, he bears his own white bite scars, including a triangular indent on the lower end of his tail. Despite being close to adulthood, he's still much smaller than the more mature Shonisaurus at 30 feet long. Thus, he still travels closely with his family, particularly with Ava. As Carlos and the rest of the pod feed, his mother rejects his close traveling, often subtly bumping him away.

Food isn't the sole purpose of these ocean titans traveling to these Californian waters. Rather, it's a necessary stop for the Shonisaurus to make on their way to their birthing grounds. Each one of the adult females is pregnant and will soon give birth to a new generation of calves. Rearing their young in shallow waters will allow them safety from predators until they're mature enough to venture back into the ocean with their mothers. It's also around this time that the older generation of calves are weaned from their mothers' care to shift focus to protecting the new.

For Carlos, this will be an especially dramatic change. While females stay within their family pods, bulls venture entirely on their own, only finding others of their kind when mating. Until his new siblings are brought into this world, the young male still travels with his grandmother, aunts, cousins, and mother. However, the latter will continue to encourage her son to maintain a distance, which is a necessary preparation for the change that will follow. With how strong of a natural bond the two have formed over the years, the separation won't be easy.

***

As the passage of time has gone on, daylight has died down. What was a mix of bright orange and pink in the sky has been replaced with a pitch black. All that remains is the almost pure white of the full moon.

This bright shine glimmers across the steady waves of darkened waters. Below the surface, beams of moonlight peer through the black veil of the night sea. Over 3,000 feet of the ocean is tinted in the clear azure blue, everything lower being concealed by darkness.

Close to the surface floats a familiar sight, but in a manner not witnessed during the day. They may have traveled to get to their destination, but the Shonisaurus pod has decided to stop and sleep. In doing so, they suspend themselves in the water, pointing their bodies upward. The only movement they make is with the current shifting them up and down like giant prehistoric buoys.

These titans may seem completely still in their peaceful state, but they're still on alert. Only one hemisphere of their brains sleeps at a time, allowing them to remain half-vigilant during their rest. Such observance is more than necessary in an ocean full of animals that could easily attempt to feed off them in their slumber.

With how close they've come on their journey, the Shonisaurus pod can afford to take one last night's sleep before arriving at the shallows the next day. Unfortunately, not all of them can wait. One female still makes her hums and rumbles through the water as she swims away. While the rest of the pod remains in their doze, one member opens his eyes to this commotion: Carlos.

Upon leaving his slumber, the young male curls and bends his body into a vertical position. He begins to search his surroundings, only finding the still, graceful, blubbery masses of his pod mates. In the distance, he begins to see something swimming away. The identity is hard to tell from how far away it is, but it roughly resembles a Shonisaurus.

Driven by curiosity, Carlos propels himself forward, past the drifting bodies of his pod. Floating closer to the figure reveals it to be none other than Ava. Like the other pregnant Shonisaurus, she has timed this migration so that by the time she gives birth, she'll already be in the safety of the shallows. However, this mother is already starting to go into labor much earlier than expected. Thus, out of instinct, she has begun trying to finish her voyage to the nursery on her own.

Carlos may not know what's happening to Ava as of now, but her higher-pitched sounds have made it clear that she's in pain. Naturally, the young male draws himself closer to his mother. Doing so only prompts the labor-ridden female to bump him away as she's done the entirety of his trip. The son ignores this but is then met with a more powerful swing from Ava's tail, knocking him further away. Confused, Carlos is left to only float while his mother travels farther from him. Torn between fear and concern, all he can do is watch as she fades away into the darker blue.

With Ava gone, Carlos begins to swim back toward the rest of his pod. As he turns, he abruptly comes to a stop. The young male peers downward to see an unusual sight for the night.

In the darkness below, shimmering bodies can vaguely be seen, along with flashes of blue glow. Luminescence of any kind is a peculiar sight at such depths, where even daylight fails to penetrate. This alone already piques Carlos' inquisitiveness.

Before Carlos can inspect this sighting, however, he first rises to the surface. There, he blows a spout of seawater from his nostrils before sucking in fresh air. How long has this young male down at such depths is uncertain, but for any marine reptile like Shonisaurus, it's always best to fill up on oxygen before such a dive. With his lungs now stocked with air, Carlos returns below the surface, starting his descent into the deep.

***

Plunging further and further into the depths uncovers a whole new part of this marine world. At nearly 1,600 feet below the surface, light is barely present, regardless of whether it's day or night. With this blinding, eternal twilight also comes colder temperatures and increased pressure.

Despite the challenges of these different waters, Carlos is well-suited for this type of exploration. As with modern whales, ichthyosaurs such as Shonisaurus have fatty tissue known as blubber. In addition to food storage and providing buoyancy while swimming, it also helps preserve body warmth while keeping out cold water. Much like crocodilians and deep-diving cetaceans, he's also able to slow his heart rate to as low as 2 beats a minute. This limits blood flow to non-essential organs, but conserves oxygen that will be used in more important areas like the brain and heart.

Even seeing in pitch darkness is no challenge for Carlos. Many ichthyosaur species share large sets of eyes, some even evolving as the biggest to be seen on any animal. Such enlarged optics allow for greater sight, especially in lower light conditions. All these adaptations combined ensure that Shonisaurus has the ability to effectively traverse these haunting depths, but only for as long as the oxygen in their bodies allow it.

With his heightened sight, Carlos bears witness to the submerged, desert-like state of the deep ocean floor. Hills and dunes of muddy sand distend beyond what even the eyes of the Shonisaurus can see. Mixed in between are a myriad of rocks of varying shapes and sizes. Some are small enough to be enveloped in the sediment of the sea floor, while others tower above like skyscrapers. The forms they take are entirely random, including jagged spikes, wide slopes, chiseled cliffs, and simple rounded stones.

Even this far down from the surface where so little light peers through, life finds a way to thrive. Across the sea bed, crabs and snails crawl around, eating whatever scraps of dead animals float down. Such a food source is rare down here, so they've evolved lower metabolisms that allow them to survive longer between meals. Clams are also present, lying buried by the sand and wedged into the crevices of the many stones.

Among these bottom-dwellers are possibly the most bizarre residents of the Triassic deep. Called Arcestes, they're a part of the spiral-shelled ammonoid subclass of cephalopods. However, they're also rather unique among this strange group. The shells they're housed are broad and rounded, giving them an almost spherical appearance. A lack of keels to stabilize them when swimming further separates them from their kin, grounding them to the ocean floor. Thus, they rely on their short yet powerful tentacles to drag them around when not feeding off shreds of loose animal material. The shells of these strange cephalopods are coal black to blend in with the stones found in the depths. Similarly, their fleshy bodies are a muddy gray to match the sand, but can change color thanks to chromatophores in their skin.

Altogether, these dwellers of the deep blend in with their sunless world. Carlos further propels himself through the black waters, finding no sign of the strange sight that drew him down here. It's only after having dove over 1,600 feet that he rediscovers the strange shine.

Growing closer and closer reveals it to be a scarce phenomenon this far from the surface... light. It's a series of bright blues that float and dance in an expansive cluster. The young male Shonisaurus slowly floats further, revealing more of these mysterious glows.

Carlos' approach also reveals that they aren't just lights, but parts of living organisms. They're a type of fairly large, ancient squid, growing up to six feet in length. The appearance of these classical cephalopods is generally the same as their modern descendants, including their small heas with prolonged mantels, large eyes, and even a single pair of larger tentacles among eight smaller arms.

It's also from these familiar frames that the glow is produced. As is the case with many of their relatives, they have specialized organs called photophores. By reacting to a mix of substances with oxygen, they're able to create their own source of light called "bioluminescence."

As many cephalopods do by changing their skin color, these squid can also change the patterns of their bodily glow to communicate. This incredible technique is incredibly convenient for them right now as they've gathered here to breed. Creating displays across their skin allows the males to show off to potential partners. Conversely, females can signal acceptance to any successful suitors. Once courtship is complete, the pairs mate by joining tentacles and exchanging sperm, all while engaging in a show of light between each other's skins.

For each of these squids, this will be the only time in their lives they'll ever be able to reproduce. Their short lifespans coupled with the energy required for breeding ensure that producing sperm and eggs will be the last things these starry cephalopods will ever do. Fortunately, the females will live longer after mating, but only so they can head to the shallows and lay their unborn young.

But even down here, death is inescapable. Carlos swims into the cloud of colorful cephalopods and starts ingesting them. Squids such as this are common prey for a Shonisaurus, especially during their early years when their teeth aren't quite as fully developed. Calves often accompany their mothers on hunts for this squishy prey, making this far from the young bull's only time. It is, however, the first he's taken without his mother by his side. He'll need to get used to this change of his status quo as whenever he meets his full size, he'll need to consume nearly half a ton of prey per day to maintain himself.

Gradually, the light of the shimmering squids disappears as Carlos consumes them. Many attempt to escape their gluttonous capture by flailing their tentacles, but their fates remain sealed in the jaws of the Shonisaurus. In their departure, they create clouds of thick, black ink to conceal them from their predator. Even this bull's well-developed eyes are unable penetrate the dark cumulus, but it doesn't halt him from biting onto each of his subsequent catches.

This male may be admirably adapted to preying on these luminous creatures, but he's not the only one who views them as food. As Carlos continues darting through the cluster of cephalopods, so, too, does another figure. It only appears as a brief, blurry shadow at first, but the Shonisaurus instinctively retreats anyway. He's only halted for a moment as the living silhouette starts ramming into and biting onto his body. Swiftly, he seeks cover behind a nearby stony spire before peering around it at the newly arrived animal. It floats across the twilight zone, only revealed by the biological light of the squids.

This is yet another ichthyosaur native to these Californian waters, Shastasaurus. Much like Shonisaurus, it too belongs to the shastasaurid family, even being the group's namesake. Despite this relation, it carries a vastly different appearance. Its body is sleeker and more torpedo-shaped with narrower flippers that aid in faster locomotion. The head is also a drastic departure from what's typically seen of ichthyosaurs, being shorter, narrower, and with a more blunt snout. Primarily, its skin is dark, bluish-gray with silver-shaded spots mottled in and an entirely white head.

At 23 feet in length, the Shastasaurus is only about half the size of a fully-grown Shonisaurus. Even Carlos in his sub-adult form is still slightly larger. Nonetheless, he still maintains his distance from this different ichthyosaur. Shastasaurus are more than capable as predators, even targeting young Shonisaurus if they see an opportunity. The young bull bears the scars of one such encounter in the form of the bite on his tail flipper. He may be much larger now, but instinct still drives him to remain out of sight. Thankfully, this is only as smaller species of Shastasaurus as much larger, 70-foot variants dwell in the waters of present-day British Columbia.

In the middle of his avoidance of the predator, a series of sounds start to emerge. They're the noises of an animal Carlos is all too familiar with, another Shonisaurus. However, they're much more strained, as if the source is in pain.

They're mixed with loud and frequent splashes, something that's quite odd to hear this far below the surface. It's only because sound travels much farther and faster in water that such a kerfuffle is audible at these depths. For all any of the sea dwellers would know, this commotion could be coming from miles away.

Nevertheless, it doesn't stop the Shastasaurus from swimming away from the squids in favor of a different meal. Carlos peers from his hiding spot to see the predator vanishing into darkness. With the combination of these sounds and what the young bull witnessed of his mother before this dive, the events that are unfolding are unmistakable.

***

As one travels further east through the Californian sea, the waters gradually become more shallow. Pitch-black depths beneath the moonlight sea begin to disappear. In their place, patches of coral become present on a much higher sea bed.

They appear in massively diverse forms, creating a vivid collage of undersea colors. Some are spheres with distinct grooves etched in like brain coral, whose name is inspired by the organ it bears an uncanny resemblance to. Others are stick-like, ends diverging into various directions like the branches of a tree. Even table-like structures rest among them, being the biggest form of coral present.

Like any large fields of these vibrant plant-like organisms, they support a variety of other marine life forms. Fish often call these reefs home, taking refuge from the occasional predatory cephalopods. As with the deeper parts of this sea, crabs, sea snails, and lobster-like crustaceans crawl amongst the coral, appearing smaller than their dark-dwelling counterparts. Even more stationary life is more plentiful in these shallow waters such as clams, crinoids, and sponges. The latter are much like coral in that their shapes vary from hollow balls to tube-like towers.

With such expansive biodiversity on display, it was hard to believe they were once absent from the ancient ocean of Panthalassa. When the Great Dying occurred over 20 million years prior, nearly 96% of all marine life had disappeared, including coral. For a time, these vibrant fields of organisms were considered extinct, but as seas became cooler and less acidic, a different lineage convergently evolved to take their place..

Thus, it's fitting that these fields of coral near the border of present-day Nevada are the sight of one of life's greatest miracles. At an oceanic cliff where these psychedelic patches meet the shadowy depths, one large, familiar animal floats in the liquid blue: Ava. Prompted by the pains of labor, the female Shonisaurus impulsively fills the water with her agonized calls. Her tail also squirms and writhes with her body, repeatedly smashing through the shimmering veil of the surface.

Gradually, Ava's body becomes more relaxed and her calls grow into silence. Yet as they do, a more concerning sight expands from her: a cloud of crimson. The dark red is so thick that it hides a quarter of her titanic bulk. It steadily grows larger as two more puffs of this scarlet shroud burst from below her tail.

From this grizzly sight, the results of this female's efforts begin to materialize: three newborn calves. At 6 feet long, each of these baby Shonisaurus is no longer than the head of their mother. They also have a few other differences from their much larger parent. Their eyes, flippers, and heads are proportionately longer, their bodies and tails shorter, their teeth smaller, and their smoother, lighter-colored skin free of any scars or parasitic crustaceans.

As animals born with lungs, the first instinct of the newborns is to breach the surface for their first breaths. Upon reentering the water, they greet their mother by twirling around and rubbing against her. During this, Ava remains still, her body tired and pained from labor.

In the shadowy blue around her, movement begins to be seen. It initially appears as a faint, stream-lined figure, barely visible in the darkness. Gradually, it draws closer and begins circling Ava and her newborns.

The moonlight around the mother and her young reveals the figure to be a familiar predator, a Shastasaurus. Due to a drastic difference in size, these smaller, slenderer ichthyosaurs often steer clear of adult Shonisaurus. However, this is a rare opportunity that no hunter could possibly pass up on. Exhausted and pained from having given birth, Ava can only float as she recovers from labor. In this state, she's also helpless in defending her youngsters from the hungry Shastasaurus.

Already, the predator darts through the water, rushing past one of the baby Shonisaurus. Ava only barely lets out a strained, deep rumble in the hopes of intimidating the attacker. Such efforts are in vain as the Shastasaurus grows bolder, coming closer with every dart around that it performs. Each time, the calves are barely able to evade, one getting grazed on one of its fore flippers. All they can do is cling to their mother, hoping her size can deter this assault.

Even this is sadly to no avail. From under the stomach of Ava, the newborns see the Shastasaurus propelling towards them. Its jaws spring open to deliver a deadly bite onto its prey.

In the blink of an eye, the hunter's attempts are halted. From the dark blue, a rival emerges, clamping its mouth onto the head of the Shastasaurus. The two sea monsters squirm and thrash as they wrestle through the water.

Soon, the Shastasaurus breaks free, swimming near the edge of visible light. From there, it spots the animal brave enough to even dare to attack it, a sub-adult male Shonisaurus. What started as an easy opportunity to prey has become much more of a challenge. If it's to feed on Ava's newborns, it'll have to go through Carlos.

Again, the Shastasaurus launches itself towards the calves at incredible speed. This pursuit is brought to a sudden halt as the bull Shonisaurus collides with it. Jaws locked, both predator and protector shake and writhe as they're compelled to the surface. Their struggle repeatedly breaks the surface, creating erupting splashes. Streams of bubbles crawl up from the bottoms of their bodies as they reenter the water, still thrashing with one another.

The Shastasaurus breaks loose once more, circling the Shonisaurus family from a safe distance. Carlos does this action coordinated with his enemy, shielding his mother and siblings. He also releases deep rumbles into the water to intimidate the predator. The moonlight also shows bleeding bite marks and thin scratches on both ichthyosaurs. Even after such injuries, both are headstrong in their efforts. Another attack is inevitable as they continue their repetitive orbits around Ava and the calves. It's only a matter of when the next strike will occur.

Once more, the Shastasaurus charges toward the feisty family. This attempt is once again interrupted, though not by Carlos. Another Shonisaurus arrives in front of the predator: a full-grown female. More of them arrive in the lunar-shined waters, joining the young bull in his defensive spiral around his mother and the newborns. Now, Ava has her whole pod around her, stuffing the liquid blue with low hums and rumbles as they revolve around their vulnerable family member. Outmatched and outsized, the Shastasaurus stands no chance against this many Shonisaurus. All it can do is retreat, vanishing into the ocean shadows.

Finally, the threat is no more, at least for the time being. Now, the pod can resume its excursion to the shallows. Only then will the newborns be safe till they are old enough to return to the high seas.

Before they do, however, Ava turns his attention to Carlos, trading a single rub mixed with a soft, soothing hum. With this over, the young bull swims away, ultimately leaving his family for good. At last, this male is ready for life alone in the open ocean.

The transition from youngster to adulthood is a challenge for many animals. Once they reach this crucial age, they must abandon the parental protections they've known all their lives and face the dangers of the wider world on their own. Despite these trying times, the bond between mother and offspring is stronger than most and rarely one to be easily broken. Carlos has easily proven this as he was more than willing to defend Ava and his newborn siblings in their final time together, even if it took surviving a dive of peril.

In loving memory of Carlos AKA Falafel

You were the best, most affectionate lap kitty any cat lover can ask for. May you rest easy beyond the rainbow bridge