Ischigualasto Formation, Argentina, 230 million years ago

    Near the western edge of South America lies what is now one small part of the giant country of Argentina. We will recognize it in some 230 million years as Valle de la Luna or the "Valley of the Moon." The region will be characterized by dry rock formations and canyons, carved out by millions of years of erosion.

    At this time, these colorful, layered sediments have yet to form. Instead, it's all dust across an arid, desert-like landscape. Much of it is a typical beige color given a dark-orange hue by the emerging light of dawn. These light-colored grains and pebbles are scattered across smooth ground, occasionally interrupted by small bumpy hills. Larger stones in the distance form cliff-shaped outcrops from which the sun sticks above.

    In addition to this dust is a sparse amount of vegetation. Much of it is drying ferns, seed ferns, and cycads, gently fading from brighter green to a more lifeless, pale shade. Trees are also present, largely being primitive conifers and ancient ginkgoes. They're scarcely seen in this dry land, making the area akin to the North American badlands of our modern day. Unlike this area, patches of scattered woodlands are present. With how few and far between these tall forms of plant life are, very few of their shadows are seen on the ground, cast by the hot scorching sun.

    Truly little wind is present, making the searing Triassic heat feel all the more intense. Though this lightly present breeze is enough to make grains of dust move across the ground. Parts of it trickle into holes carved into the earth. What lies inside is concealed by shadow, but the resident of one of them begins to emerge.

    This is Hernan, a male Eoraptor and one of the first dinosaurs. He is a small animal, reaching 3 feet long and weighing no more than 20 pounds. Even so, his size is immensely outweighed by the greatness in store for his descendants.

    As a Saurischian, he's part of a lineage that will one day give rise to sauropods such as Brontosaurus and Brachiosaurus. However, his body plan is similar to that of a theropod dinosaur like T-Rex and Velociraptor. Everything from his elongated hindlimbs, three-toed feet, stiffened long tail and hands share this resemblance, though it has five fingers as opposed to two or three. Even his head is shaped more familiarly to a theropod than to a sauropod, being pointed with a near-triangular shape. Despite how lightly built this skull is, it has large, forward-facing eyes. A narrow snout ends in a mouth full of sharp, serrated teeth. His scaly skin is primarily a dull, earthy brown with beige vertical stripes on his back and an underbelly of the same color. A light coat of muted gray feathers is present, too, primarily restricted to the upper back and shoulders.

    By nestling in holes like these, Eoraptors like Hernan can rest while avoiding the sweltering heat of the sun. Even so, he readily steps out of his spot of comfort and onto the desiccated surface. Only one force is driving him to take such steps: hunger.

    With how desolate the badlands around him are, Hernan won't be able to quench his desire for food here. For that, he starts to sprint away from his subterranean home to a different part of his environment.

    Even just walking won't be easy for this Eoraptor. The sun constantly barrages the ground with over 80-degree heat. As a warm-blooded animal, staying in such torrid light for too long can mean death.

    Thankfully, Hernan has a solution. Periodically, he seeks temporary shelter behind larger, dried-up ferns. Each one is just big enough to encapsulate the Eoraptor in a cooling blanket of shadow.

    Occasionally, there will be batches of this dead greenery larger than others. Upon stopping at one of these, Hernan passes with caution. Low breathing permeates the air around it, sending shivers down the small dinosaur. He's not able to see much of the larger animals making such snores. Only a tail and the tip of the nose stick out of the dust, the scaly skin matching in color to help blend in. The Eoraptor takes extra caution passing by it. Any faster could risk alerting the large animal.

    It only takes him seconds, but Hernan finally passes the slumbering beast. From here, he leaves the scorched scrubs behind, heading toward the wooded entrance to a canyon. The forestry is light, but it's already more trees than are present in the area he's leaving. This is only one indicator that he's going in the direction he needs to.

***

    As he travels down the canyon, vegetation starts to become much more plentiful. The ground grows ever more plentiful in low-lying plants, though still scattered across the dusty ground. Even though the amount of trees has increased from the badlands outside the canyon, they have yet to block out the sky and the towering cliffs.

    As Hernan sprints through the wooded gorge, he finds that life here thrives in greater frequency. Arthropods thrive in plentiful numbers, including millipedes, spiders, and beetles. The deadliest are scorpions whose tail stings are painful for even the biggest animals around.

    But even these aren't exempt from predators. Scorpions and the many other arthropods here are prey to Eoraptors such as Hernan. Through his swift speed, he quickly snatches up any finds within reach of him. He's so fast, he even outruns the small, lizard-like reptiles he competes with.

    However, this isn't his primary destination. Rather, a quick pit stop on the way to a bigger goal. If he's going to satiate his hunger, he'll need to visit a bigger source. Thankfully, it isn't long before he arrives at such a place.

    Deep within the gorge is a small pond. Much of it has been dwindled by the heat, but there's still a substantial amount left. The water here appears a murky brown, but it's still a magnet attracting those who rely on it, of which there are many. This local fauna comes in varying shapes and sizes, all of which dwarf Hernan.

    The most common is the slow-moving Ischigualastia, a member of the bizarre dicynodont clade of therapsids. At up to 11 feet long and weighing up to a ton, they are the largest of their clade to have been discovered in South America. Compared to other dicynodonts, they're only outsized by a later relative from modern-day Poland.

    Their short, thick legs are held in a sprawling gait, ending in wide, blunt feet with stout claws. These limbs support bulky, barrel-shaped bodies with heavy chests, wide hips, and short, stocky tails. Their heads are large and somewhat boxy with a wide, flattened skull that dominates their appearance. Their mouths lack teeth, instead possessing a tough, tortoise-like beak built for biting through fibrous plants. This beak lies between the only teeth they have, a pair of short, curved, bony tusks that extend downward from the upper jaw. Their leathery skin is primarily a brownish gray with sparse white hairs scattered all over.

    The Ischigualastias are humble species, primarily plodding around and eating any lower vegetation they find. As they do, they fill the area with the sounds of their honking and grunting. Due to their body plan, they are restricted from reaching the tall branches that hang out of their reach. Even so, there is one animal here that experiences no such difficulty.

    Towering over everything here is the occasional Sillosuchus. In appearance, its body shape is similar to a theropod dinosaur, but with the moderately long neck of a primitive sauropod. Despite such similarities, it's a type of unrelated reptile whose lineage is more intricately linked to modern crocodilians.

    One of the other far cries from its extant relatives lies in its diet. The jaws of its small, narrow head lack any teeth. Instead, it has a beak at the tip of its mouth with which it bites off any plant matter its long, slightly curved neck can allow it to reach. Its slender, 33-foot-long body tapers to the tip of a lengthy, thick tail. Although the sleek, muscular hind limbs are what support its form, its forelimbs are much shorter and held close to its chest. Its scaly skin is primarily fossil gray with a lighter underbelly.

    With a greater abundance of greenery in the wooded canyon, herbivores like Ischigualastia and Sillosuchus are easily drawn here like moths to a flame. The waters of the pond also provide another vital resource in the form of hydration. However, they aren't the only ones that rely on this body of reflective liquid.

    Around the pond, hundreds of dragonflies dart and buzz through the air. They are mostly males, engaging in aerial acrobatics and territorial battles. Success will earn them the right to mate with the resting females, who choose their partners based on flying prowess. Once pairs form, they mate in mid-air, the males using claspers at the ends of their tails to connect to the females and form a wheel.

    But it's not just dragonflies that look forward to this annual event. Predators come here to feast on the plentiful aerial insects. One of which resides in the waters that the dragonflies have gathered around, their jaws bursting from the surface to trap their prey.

    These are Pelorocephalus, an Argentinian member of the temnospondyl branch of amphibians. Like all members of this extinct order, their muscular, streamlined bodies greatly resemble that of a salamander. Their limbs are short but powerful, ending with webbed toes that aid them in swimming. Long, laterally compressed tails further adapt them to a semi-aquatic lifestyle. Their heads are broad and flattened, having a triangular shape that resembles a spade. Sharp, cone-like teeth line their jaws, making them perfect for trapping their prey. The eyes are positioned high on their head, allowing them to see above the water's surface while being mostly submerged. Their smooth, permeable skin is a muddy brown with darker spots scattered all over, blending them in with the murky pond.

    While Pelorocephalus hunt the dragonflies from the water, another animal feeds on them from dry land: Hernan. His lightweight frame and strong hind limbs allow him to spring high off the ground and snatch any of the flying insects that fly within reach. Such a form is also well adapted for speed, allowing him and other Eoraptors to catch up to any dragonflies that attempt to escape the grasp of his jaws.

    Often, it's mating pairs that are the little dinosaur's preferred target. Not only does it allow him a bigger meal in one bite, but mating makes them slower fliers than they would be when traveling alone. Even so, one connected couple proves to be a challenge for the experienced hunter. Repeatedly, he springs up and snaps his jaws at the mating dragonfly pair, only for the insects to dart and dodge out of the way. Hernan's pursuit of this troublesome quarry makes him run in circles, even sending him away from the edge of the pond.

    Quickly, the male Eoraptor finds himself chasing his irksome prey into a thick batch of greenery. At times, he can barely see the dragon flies through the leaves of the plants around him. However, their buzzing allows him an audible trail to follow.

    This method of tracking his prey quickly leads Hernan somewhere unexpected. Suddenly, the Eoraptor finds himself tumbling down a dry dirt cliff. He briefly tumbles along it, kicking up clouds of dust around him. One last larger puff erupts upon impacting the ground below.

    Immediately, Hernan springs back onto his feet. He darts his head around, observing the area in which he arrived. It's a small, plantless grove surrounded by more of the same greenery. In the middle, however, is a crater as long as him in diameter. He steps forward to peer into it, finding over a dozen eggs tightly packed in and leaves protecting them from the sun.

    For Herna, this can be another opportunity to feed himself. Unfortunately, nests like this are rarely without anything guarding it. As the Eoraptor reaches his head toward an egg, he begins to hear shrill hisses around him. Such spine-chilling sounds prompt him to freeze like a statue. He looks around finding two pairs of similar-looking, three-toed legs around the nest, each one easily outsizing his own. Peering upward reveals the parents of the nest's eggs.

    Staring down at Hernan is a pair of Herrerasaurus. These too are dinosaurs, but are much larger at up to 20 feet long. They also have a body plant that greatly resembles that of theropod dinosaurs. Like Eoraptor, they too aren't related, instead being a part of a lineage that unfortunately won't survive past the end of the Triassic.

    Two long, powerful hind legs support each of their slender yet muscular bodies, allowing them to tower four feet above Hernan. Forelimbs are present as well, being much shorter and ending in five-fingered hands. The thumbs and first two digits have sharp, curved claws while the fourth and fifth ones are stubbier and lack such talons. Long, stiff tails extend from their rears, helping to balance their overall form. Short, strong necks support lengthy, narrow heads, shaped like an elongated wedge. They sport a pair of forward-facing eyes, long, tapered snouts, and jaws filled with serrated teeth. Their scaly skin is primarily greenish brown with a beige underbelly. Like the Eoraptor, they have a coat of light feathers on the same parts of their bodies, being dull brown.

    Shaken by the sight of the Herrerasaurus pair, Hernan gently steps backward from them. Both of the larger carnivores spire above him as they hiss and growl.

However, only one approaches the Eoraptor, the male. He's distinguished by a bright red coloration on the scales of his throat. As the primary guard of this nest, he's been forced to stave away from eating for weeks on end. Not only is it parental instincts driving him to the Eoraptor, but hunger as well.

In a split second, the male Herrerasaurus lunges toward his prey. Hernan quickly sidesteps this attack, narrowly avoiding his jaws. He dodges more subsequent lunges as he scrambles up the dirt cliff he fell from.

Upon reaching the top, the Eoraptor darts away. In his wake, the Herrerasaurus steps up as well before charging after him. Being a much larger animal, he experiences no difficulty in traversing over the cliff.

The chase of the two primitive dinosaurs takes them through the greenery of the canyon. Sounds of rustling and branch snapping are mixed in with the usual ambiance of insect buzzing and Ischigualastia grunting. The forms of the Eoraptor and Herrerasaurus appear almost like a blur as they spring through the vegetation around them.

Reaching close to Hernan, the Herrerasaurus begins to draw his jaws agape. He lunges toward his prey, snapping his jaws. However, the Eoraptor disappears in a narrow duck. The larger carnivore turns around, its feet skidding across the dirt ground.

His eyes comb over the area around him, stopping at a single hole. The inside is almost entirely pitch-black, hiding the underground contents. Inside, Hernan remains still, waiting for the right time to exit.

Suddenly, a bark-like hissing sound appears from behind the Eoraptor. He jumps in surprise as he turns around. Doing so reveals to him the source of such noise.

It's the true resident of this burrow, a bizarre Hyperodapedon. This animal's body greatly resembles that of a lizard, albeit one that reaches 6 feet in length. Everything from its short, sprawling limbs, clawed feet, and long, tapering tail are similar to the familiar reptiles they're distantly related to. What sets it apart is its head, starting broad before narrowing to a thin beak. The top resembles a bird of prey bill while the bottom splits into two tips resembling buck teeth. Such a combination of features makes it appear as a cross between a lizard and a naked mole rat. Its scaly skin is primarily a reddish brown with sparse tints of green.

Although a vegetarian, the appearance and attitude of the Hyperodapedon are enough to intimidate Hernan. He backs away from the strange reptile only to be stopped by what's after him from above. The jaws of the Herrerasaurus poke into the burrow, constantly snapping. Stuck between two different larger animals, the lone Eoraptor seemingly has no way of escape.

However, with the emergence of loud honks and grunts, Hernan's predicament starts to change. The Herrerasaurus pulls his mouth out of the entrance of the burrow. Doing so reveals sunlight passing in from the surface above.

Hernan approaches the hole, proceeding to stick his head out. He not only spots the Herrerasaurus, but also a small group of Ischigualastias standing in front of it. The large herbivores bellow and honk while waving their tusks around. Meanwhile, the predator steps backward, hissing at the bulky dicynodonts. With his pursuer distracted and the burrow's owner being unwelcoming, Hernan takes the chance to climb out and dart away into the vegetation. Doing so, however, doesn't elude the eyes of the Herrerasaurus.

***

It isn't long before Hernan reenters the sun-scorched badlands he previously left. Stepping onto its dusty, gravelly surface greets him with a baking heat with each step. Despite such conditions, he continues with his run.

Most animals by now would have given up from pure exhaustion. As an Eoraptor, however, Hernan has a biological trick up his sleeve. In his body is a series of air sacs from which air is constantly flowing. This grants him the ability to store oxygen without staying still or walking in a specific way like with crocodilians. Not only that, but he's also able to maintain his speed for a much longer period.

Unfortunately for Hernan, so does his pursuer. These biological advantages greatly help in outpacing non-dinosaur predators but allow the likes of Herrerasaurus to pursue prey for greater lengths. Even well outside of the wooded canyon, the hunt continues.

For the first time in a while, Hernan begins to slow down. A brief trip quickly follows this decrease in speed. Upon crashing into the ground, he shakes his head free of dirt. As he does, however, he starts to hear the sound of shifting dust. Turning around not only reveals the Herrerasaurus approaching from the distance but also a tail retreating. Hernan looks to his left, seeing a whole nother animal begin to emerge from a pile of dust. Sounds of spilling grains mix in with a deep, gurgling hiss. As the Eoraptor retreats to cover, the Herrerasaurus is forced to freeze, staring up at the towering creature.

This is an animal much larger than both Hernan and the Herrerasaurus. It's known only as Saurosuchus, the "lizard croc." This massive, 23-foot-long, half-ton reptile is one of the largest members of the rauisuchians which dominate much of Pangea in the Triassic.

Its appearance is similar to its many other relatives, having a heavily built, croc-like body, four pillar-like legs, and a long, muscular tail. A large, boxy head sports an elongated, robust snout, two high-positioned eyes, and powerful jaws filled with massive, serrated teeth. The skin of this reptile is made up of pebbly scales mixed with armored, croc-like scutes and ridges. Primarily, this skin is a dusty beige to blend in with the ground around it with darker taupe on its back.

Saurosuchus, like many other rauisuchians, is capable of temporarily swapping between a quadrupedal and bipedal stance. Using this adaptation, he rears up on his hind legs like a modern bear. Combined with its intense hisses, it becomes a frightening display as it towers over the Herrerasaurus. Trapped below its creeping shadow, the now-smaller predator steps back slightly while letting out soft hisses. Outmatched, the Herrerasaurus retreats to the wooded canyon, prompting the Saurosuchus to return to the dust.

From farther away, Hernan finds a hole in the ground. He peers his head in, finding nothing but the interior he's become accustomed to. Having returned to home sweet home, the Eoraptor climbs in and curls up. Having heavily worked himself, it doesn't take long for him to curl up and enter a deep slumber.

The dinosaurs are a race destined to one day inherit the Earth. For now, however, they live in the shadow of many reptile groups that have evolved before and alongside them. While larger members like Herrerasaurus have begun to evolve, many remain small like Eoraptor. They may have a long way to go before they dominate the planet, but their presence alone already signals the birth of a dynasty.