The Fascinating World of Dinosaurs: Origin and Diversity

Discovering how these giants of the past lived, who they were, and why they became extinct has generated a great deal of excitement and remains a subject of ongoing study today.

In Chapter 6, “Origin and Diversity of Dinosaurs”—written by Bernat Vila, Marc Furió, and Josep Marmi, and included in the book Dinosaurs of the Levantine Peninsula—they explain the origin of the first dinosaurs and the great diversity they eventually achieved.

First, it is essential to understand and contextualize the climatic and environmental conditions that existed at that time: the environment and climate were harsh. During the Triassic period, one of the greatest ecological catastrophes occurred: the extinction of a high percentage of marine and terrestrial life. This created a challenging period, during which the continental masses formed a supercontinent called Pangea. Unfortunately, this landmass caused extreme temperature fluctuations and scarce rainfall, which led to extinctions but also allowed animal life to thrive in areas with more favorable climates. Consequently, there was significant diversification and evolution among various vertebrates.

This brings us to the reptiles known as “archosaurs” and the first dinosaurs: both took advantage of the adverse conditions to evolve.

Between the end of the Middle Triassic and the middle of the Late Triassic—we’re talking about some 225 million years ago—various reptiles went extinct, and the first radiation of archosaurs and early dinosaurs took place, such as Lagerpeton or Marasuchus and some large rauisuchids (the latter very similar to modern crocodiles), as well as Saurosuchus, large predators about 5 meters long.

Specifically, the earliest dinosaurs were reptiles already present in the Late Triassic that belonged to all the major dinosaur lineages: the Herrerasaurids and Eoraptor (carnivores), Pisanosaurus (herbivore), and sauropods such as Antetonitrus and Isanosaurus.

The earliest forms of dinosaurs were moderately sized, light bipeds less than 6 meters long, with an upright posture. Their movements were more agile, allowing for greater speed and less wear and tear. The shape of the skull and jaw was also adapted to the environment, making it easier to grasp prey, and the muscles allowed for more efficient grinding of food.

Dinosaurs from those eras inhabited nearly every region and adapted to diverse climates and environments. Thanks to the fossil record, we can now understand how they adapted, the diversity of the different groups, and how many species of dinosaurs inhabited the Earth; but there is still much to explore and discover about this fascinating world.