Herrerasaurus

MEANING: Herrera's lizard

PERIOD: Late Triassic

CONTINENT: South America

Herrerasaurus is a basal saurischian dinosaur, and one of the earliest dinosaurs from the fossil record. It was a lightly built bipedal carnivore with a long tail and a relatively small head. Adults grew to 6 m in total length and 350 kg in weight, making Herrerasaurus the largest known carnivorous dinosaur of its time.

Herrerasaurus is from the Late Triassic. The Triassic is the first geologic period of the Mesozoic, spanning from the end of the Permian Period 252 million years ago to the beginning of the Jurassic 201 million years ago. Both the start and end of the Triassic were marked by major extinction events. In the aftermath of the devastating Permian-Triassic extinction, life gradually rebounded, giving rise to new groups that would shape the Mesozoic Era. The global climate during the Triassic was mostly hot and dry, with vast deserts dominating the interior of the supercontinent Pangea. Over time, as Pangea began to rift apart, the climate slowly became more humid, creating new environments and opportunities for ecological diversification.

For much of the Triassic, dinosaurs were not yet the dominant terrestrial animals. Instead, the land was populated by a variety of other reptiles, including sprawling archosaurs. Early synapsids, the lineage that would eventually lead to mammals, were also still present but declining. Vegetation was dominated by drought-tolerant plants such as seed ferns, cycads, ginkgoes, and early conifers. These hardy plants formed the base of recovering ecosystems during this volatile time.

It wasn't until the Late Triassic, around 230 million years ago, that the first true dinosaurs appeared. Early forms were small, bipedal, and lightly built, likely preying on insects and small vertebrates. While they remained minor players compared to other reptilian groups, their agility, upright stance, and efficient breathing gave them advantages that would prove crucial in the long run. As the Triassic drew to a close, another mass extinction event reshaped life on Earth once again—wiping out many of the dominant reptile groups and clearing the way for dinosaurs to rise to prominence in the Jurassic.

Herrerasaurus is a herrerasaurid. Herrerasauridae is a family of early, basal carnivorous dinosaurs that lived during the Late Triassic. These dinosaurs are often considered basal theropods due to their bipedal stance, sharp teeth, and carnivorous diet. However, there is ongoing debate about their exact placement within the dinosaur family tree. Some paleontologists argue that herrerasaurs may not be true theropods at all, and could instead be more basal saurischians, or even entirely outside of Dinosauria. This uncertainty stems from their mix of features seen in both early dinosaurs and more primitive archosaurs, making their exact evolutionary relationships somewhat ambiguous.

Herrerasaurids were small in terms of Mesozoic theropods, but they were relatively large by Triassic standards, with some species reaching lengths of up to 6 m. Compared to smaller basal theropods, herrerasaurids were more robust, with long, powerful legs, a large skull, and sharp teeth adapted for carnivory. Their bodies were built for speed and hunting, with long tails for balance and relatively short arms. While they shared many features with later theropods, their overall build was less specialized, reflecting their early position on the dinosaur evolutionary tree.