Herrerasauria
Early carnivorous dinosaurs of uncertain evolutionary position.
Herrerasauria is an extinct clade of carnivorous dinosaurs that first appeared in the fossil record around 231–230 million years ago during the Carnian stage of the Late Triassic. While many herrerasaurids are known from the Carnian, some possible remains (e.g., from Poland) are Norian in age, so the exact timing of their extinction remains uncertain. Their phylogenetic position is uncertain: they may be basal theropods, basal saurischians, or even a lineage branching from Dracohors separate from Dinosauria. They are among the oldest known dinosaurs and are not considered ancestral to any later dinosaur group.
Quick Facts
- Taxon
- Herrerasauria
Facts from the source article.
Lore & Background
Herrerasaurids were first discovered in South America, with Staurikosaurus found in the 1930s and Herrerasaurus in the 1960s. A nearly complete skeleton of Herrerasaurus ischigualastensis was unearthed in the Ischigualasto Formation in San Juan, Argentina, in 1988. Less complete possible herrerasaurids have been reported from North America, Africa, Europe (Norian-age fossils in Poland), and Zimbabwe (Carnian Pebbly Arkose Formation).
Reader's Guide
Herrerasauria's significance lies in its basal position among early dinosaurs and the ongoing debate about its classification. Their anatomy is a mix of primitive and derived traits: a partly open acetabulum, only two sacral vertebrae (the fewest among dinosaurs), a posteriorly rotated pubic bone with a tetanuran-like expansion, a hand with five metacarpals but only three long fingers with curved claws, and a hinged mandible also seen in theropods. Phylogenetic analyses have placed them as basal theropods, basal saurischians, non-eusaurischian saurischians, or even outside Dinosauria. The 2017 analysis by Baron, Norman, and Barrett found Herrerasauridae as sister to Sauropodomorpha within Saurischia. In 2024, Andrea Cau reclassified Herrerasauria within Theropoda. A 2026 study by Srivastava and Nesbitt placed Herrerasauria basal to Saurischia and named the new clade Morphoraptora for related taxa. This uncertainty reflects the difficulty of correlating late Triassic land-animal-bearing beds.
Did You Know?
- Herrerasaurids had only two sacral vertebrae, a trait shared with some other early dinosaurs (e.g., Eoraptor), so it is not uniquely the lowest among all dinosaurs.
- The holotype specimen of 'Frenguellisaurus ischigualastensis' (now a synonym of Herrerasaurus ischigualastensis) may have reached about 6 meters (20 ft) long.
- A hinged mandible, also found in theropods, is present in herrerasaurids.
- The clade Herrerasauria was first phylogenetically defined by Langer (2004) as the most inclusive clade containing Herrerasaurus ischigualastensis but not Passer domesticus.
Frequently Asked Questions
What is Herrerasauria?
Herrerasauria is a small clade of early carnivorous dinosaurs that ranks among the oldest known dinosaur forms. They were meat-eating animals that first show up in the Late Triassic fossil record.
When did Herrerasauria first appear?
The earliest herrerasaurid fossils are dated to roughly 231–230 million years ago, placing their debut squarely in the Carnian stage of the Late Triassic. This makes them one of the first dinosaur lineages we can identify in the geological record.
Where do herrerasaurids sit in the dinosaur family tree?
Their exact phylogenetic position is still hotly debated among paleontologists. Depending on the study, they may be basal theropods, basal saurischians, or even a Dracohors lineage that branched off before Dinosauria proper formed.
Why are herrerasaurids important to dinosaur history?
Because they are among the earliest recognizable dinosaurs, they give us a rare snapshot of what the very first dinosaur body plans looked like. They are not regarded as direct ancestors of later dinosaur groups, but they help illustrate the initial burst of dinosaur diversity.
When did Herrerasauria go extinct?
Most herrerasaurid material comes from Carnian-age rocks, implying they vanished by the end of that stage around 228 million years ago. A handful of possible remains from Poland may push their range into the Norian, so the precise timing of their disappearance is still uncertain.
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