Prehistoric Wild: Life in the Mesozoic

Birth of a Dynasty (230 MYA)

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 greatly 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.