A predator before the age of dinosaurs
In the arid badlands of northwestern Argentina lies the Ischigualasto Formation, a geological trove that holds the remains of one of the earliest dinosaurs, Herrerasaurus ischigualastensis. This creature walked the Earth approximately 231.4 million years ago during the Late Triassic Period. At that time, this region was not a desert but a volcanically active floodplain with rivers and rich vegetation. Petrified tree trunks over 40 meters tall have been found here, evidence of a once-lush environment.
Herrerasaurus was a bipedal carnivore, measuring between 3 and 6 meters (10 to 20 feet) in length and weighing an estimated 210 to 350 kilograms (463 to 772 pounds). It had a long tail and a relatively small head for its size, with a skull measuring up to 56 centimeters (1.8 feet) long. Its jaws were filled with large, serrated, backward-curving teeth, ideal for a meat-eater. A peculiar feature of Herrerasaurus was a flexible joint in its lower jaw, which allowed it to slide back and forth to secure a better grip on struggling prey. Its forelimbs were less than half the length of its hindlimbs and equipped with three long, curved claws for grasping.
An evolutionary puzzle
The classification of Herrerasaurus has long been a subject of debate among paleontologists. It possesses a mosaic of features seen in different dinosaur groups, as well as more primitive traits found in non-dinosaurian archosaurs. This has led to its placement as a basal theropod, a basal saurischian, or even just outside the dinosaur family tree entirely. This anatomical mix shows a time when the dinosaur lineage was just beginning to diversify.
The first fossils were discovered in 1959 by a local goatherd, Victorino Herrera, for whom the dinosaur is named. Paleontologist Osvaldo Reig officially described the species in 1963. These initial finds were fragmentary. A nearly complete skeleton, including the first complete skull, was not found until 1988 by a team led by American paleontologist Paul Sereno. This discovery provided critical information about its anatomy. In the Ischigualasto Formation, dinosaurs were not dominant. Their fossils make up only about 6-11% of the total tetrapod specimens found. The ecosystem was filled with other reptiles, such as rhynchosaurs and large carnivorous archosaurs like Saurosuchus, which would have preyed on Herrerasaurus.