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Brown, lean early dinosaur running in side view with a long tail
Life reconstruction of Herrerasaurus ischigualastensis with speculative colouration, based on 2019 understanding of its anatomy.Image credit: PaleoNeolitic, CC BY-SA 4.0, via Wikimedia Commons (unmodified except resizing)CC BY-SA 4.0 (unmodified)Source (opens in a new tab)

Herrerasaurus ischigualastensis

Pronounced heh-RARE-ah-SORE-us ish-ee-GWAH-las-TEN-sis

Saurischia · Herrerasauridae

One of the earliest known dinosaurs, a two-legged predator from the Late Triassic of north-west Argentina, about 230 million years old. A complete skull found in 1988 showed it was an agile hunter with grasping hands.

  • Bipedal
  • Apex predator
Compare
Period
Triassic· Late Triassic
Diet
Carnivore
Length
4.5–6 m
Mass
200–350 kg
Location
San Juan Province, Argentina

Quick answers

How big was Herrerasaurus ischigualastensis?
Herrerasaurus ischigualastensis was about 4.5–6 m long. It stood about 1–1.3 m tall at the hips. It weighed about 200–350 kg. (Wikipedia: Herrerasaurus 2026; Sereno & Novas 1992)
When did Herrerasaurus ischigualastensis live?
Herrerasaurus ischigualastensis lived during the Late Triassic, about 237–227.3 million years ago. (Paleobiology Database: Herrerasaurus occurrences 2026; Martinez et al. 2011)
Where have Herrerasaurus ischigualastensis fossils been found?
Fossils of Herrerasaurus ischigualastensis have been found in Ischigualasto Formation (San Juan Province) and Argentina. (Reig 1963; Sereno & Novas 1992)
What did Herrerasaurus ischigualastensis eat?
Herrerasaurus ischigualastensis was a carnivore. (Reig 1963; Sereno & Novas 1992)
Who named Herrerasaurus ischigualastensis, and when?
Herrerasaurus ischigualastensis was described by Osvaldo A. Reig in 1963. (Reig 1963; Paleobiology Database: Herrerasaurus occurrences 2026)

On this page

Period
Triassic237–227.3 Ma
Diet
Carnivore
Length
4.5–6 m
Mass
0.2–0.4 t
Location
Argentina
Classification
Saurischia · Herrerasauridae
Described
1963, Osvaldo A. Reig

Overview

Herrerasaurus ischigualastensis lived about 230 million years ago in the Late Triassic, in the river valleys of what is now San Juan Province, Argentina. The goatherd Victorino Herrera noticed its bones in the Ischigualasto Valley in 1959, and Osvaldo Reig named it after him in 1963.

For decades it was known only from partial skeletons, and its place in the family tree was unclear. In 1988 a team led by Paul Sereno found a complete skull and skeleton; Sereno and Fernando Novas (1992) showed it was an agile, two-legged predator with short, grasping and raking forelimbs.

It lived at a time when dinosaurs were still rare. The Ischigualasto Formation records the first dinosaurs as dominant carnivores and small herbivores, alongside rhynchosaurs, cynodonts and large crocodile-line reptiles (Martinez et al. 2011).

Name meaning

"Herrera's lizard", after Victorino Herrera, who found the first remains; ischigualastensis for the Ischigualasto Valley (Reig 1963).

Biology & evidence

What scientists think about how this animal lived, and how strong the evidence for each idea is.

Locomotion

  • Herrerasaurus was an agile two-legged predator with grasping hands.

    Evidence level: Strong evidence

    Its complete skeleton shows long hind limbs and short arms with claws for grasping and raking.

    Evidence for / against · 1
    Evidence for

    • Specimen · Complete Herrerasaurus skull and skeleton

      A complete skull and skeleton found in 1988, showing a bipedal predator with short forelimbs specialised for grasping and raking.

Other

  • Herrerasaurus was an early theropod.

    Evidence level: Disputed

    Sereno and Novas called it a primitive theropod; other analyses place herrerasaurids just outside the theropods or outside the saurischian split.

    Evidence for / against · 1
    Evidence for

    • Specimen · Complete Herrerasaurus skull and skeleton

      A complete skull and skeleton found in 1988, showing a bipedal predator with short forelimbs specialised for grasping and raking.

  • Herrerasaurus is one of the oldest known dinosaurs, about 230 million years old.

    Evidence level: Strong evidence

    Its rocks are dated by radiometric methods to the mid Carnian of the Late Triassic, among the earliest records of dinosaurs anywhere.

    Evidence for / against · 1
    Evidence for

    • Other · Ischigualasto faunal record and radiometric ages

      Biozones and 40Ar/39Ar ages bracketing the Ischigualasto Formation, showing early dinosaurs as dominant carnivores about 230 million years ago.

Size

Length
4.5–6 m

(19.7 ft)

Height
1.1 mpublished range 1–1.3 m

(3.6 ft)

Based on largest individuals (femora c. 0.47 m)

Mass
200–350 kg
Herrerasaurus ischigualastensis was about 6 m (19.7 ft) long, roughly 3.3 times the height of a 1.8 m adult human.

Timeline

Lived from about 237 to 227.3 million years ago (Ma), within the Mesozoic era (252–66 Ma).

Periods: Late Triassic (237–201.4 Ma), Triassic (251.9–201.4 Ma)

Carnian bounds of the type collection in PBDB (PBDB time scale). Martinez et al. (2011) bracket the formation with 40Ar/39Ar ages and place its early dinosaurs about 230 million years ago (mid Carnian).

Location

Formations

Map data: Natural Earth (public domain). Modern positions, not where the continents were then.

These are the places where fossils have been found, not the full area where the animal lived.

Ecosystem

Lived in: Ischigualasto

231.7–225 million years ago · floodplain, river system

Late Triassic river floodplains of north-west Argentina with cool temperatures and strongly seasonal rainfall; the earliest dinosaurs lived among rhynchosaurs, cynodonts and crocodile-line reptiles.

Classification

  1. cladeDinosauria
  2. cladeSaurischia
  3. familyHerrerasauridae
  4. genusHerrerasaurus
  5. speciesHerrerasaurus ischigualastensis

Taxonomic status: Valid

Fossil record

Herrerasaurus skeleton at the Field Museum of Natural History, Chicago.Image credit: Zissoudisctrucker, CC BY-SA 4.0, via Wikimedia Commons (unmodified except resizing), Field Museum of Natural HistoryCC BY-SA 4.0 (unmodified)Source (opens in a new tab)
Specimens
Catalog numberStatusInstitutionFound
PVL 2566HolotypeInstituto Miguel Lillo (PVL)1959

Which bones each specimen preserves has not been recorded yet.

Skull of Herrerasaurus PVSJ 407 in left lateral view and maxilla PVSJ 053, from Alcober & Martinez (2010).Image credit: Oscar Alcober, Ricardo Martinez, CC BY 3.0, via Wikimedia CommonsCC BY 3.0Source (opens in a new tab)

All specimens

Discovery

Year described
1963
Described by
Osvaldo A. Reig
Type specimen
PVL 2566

Discovery timeline

  1. 1959 · First material found

    Victorino Herrera finds bones in the Ischigualasto Valley

    A goatherd notices dinosaur bones near San Juan.

    People: Victorino Herrera

  2. 1963 · Formally described

    Reig names Herrerasaurus

    Osvaldo Reig names the dinosaur after its finder.

    People: Osvaldo A. Reig

  3. 1988 · Specimen recovered

    Complete Herrerasaurus skull found

    A team led by Paul Sereno finds a complete skull and skeleton, described in 1992.

    People: Paul C. Sereno, Fernando E. Novas

Sources

  1. (2026). Paleobiology Database: Herrerasaurus occurrences. The Paleobiology Database (paleobiodb.org), data service 1.2, accessed 2026-09-23. https://paleobiodb.org/data1.2/occs/list.txt?base_name=Herrerasaurus&show=coords,paleoloc,strat,loc,ref&pgm=gplates (opens in a new tab)
  2. (2026). Wikipedia: Herrerasaurus. Wikipedia (English), accessed 2026-09-23. https://en.wikipedia.org/wiki/Herrerasaurus (opens in a new tab)
  3. Martinez, R. N., Sereno, P. C., Alcober, O. A., Colombi, C. E., Renne, P. R., Montañez, I. P. & Currie, B. S. (2011). A basal dinosaur from the dawn of the dinosaur era in southwestern Pangaea. Science 331: 206-210. doi:10.1126/science.1198467 (opens in a new tab)
  4. Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs (2nd edition). Princeton University Press.
  5. Reig, O. A. (1963). La presencia de dinosaurios saurisquios en los "Estratos de Ischigualasto" (Mesotriásico Superior) de las provincias de San Juan y La Rioja (República Argentina). Ameghiniana.
  6. Sereno, P. C. & Novas, F. E. (1992). The complete skull and skeleton of an early dinosaur. Science 258: 1137-1140. doi:10.1126/science.258.5085.1137 (opens in a new tab)