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Temporal range: Upper Triassic
231.4 mya
Mounted cast of skeleton, Senckenberg
Scientific classification
Skeleton of Herrerasaurus and Eoraptor
Skull of dinosaur with long jaw, teeth, and hollow head
The most complete skull, specimen PVSJ 407, and left maxilla PVSJ 053

Herrerasaurus was one of the earliest dinosaurs. All known fossils of this carnivore have been discovered in Upper Triassic strata dated to 231.4 million years ago (mya) in northwestern Argentina.[1]

It is a member of the Herrerasauridae, a family of similar genera that were among the earliest dinosaurs.[2][3]


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Herrerasaurus was a lightly built bipedal carnivore with a long tail and a relatively small head. Its length is estimated at 3 to 6 meters (10 to 20 ft),[4] and its hip height at more than 1.1 meters (3.3 ft).[5] It may have weighed around 210–350 kilograms (463–772 lb).[5]

In a large specimen the skull measured 56 centimeters (1.8 ft) in length.[5] Smaller specimens had skulls about 30 centimeters (1 ft) long.[6]

The tail, partially stiffened by overlapping vertebral projections, balanced the body and was also an adaptation for speed.[6]


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The paleoenvironment of the Ischigualasto Formation (where it was found) was a volcanically active floodplain covered by forests with seasonal rainfall. The climate was moist and warm,[7] with seasonal variations.[8] The vegetation was ferns, horsetails, and giant conifers. These plants formed lowland forests along the banks of rivers.[4] Herrerasaurus was the most common of the carnivores of the Ischigualasto Formation.

Herrerasaurus lived in these jungles alongside a smaller dinosaur, the one metre long Eoraptor. Saurosuchus,[9] a huge quadrupedal Archosaur was the biggest land predator at the time. There were also a number of therapsid and reptilian herbivores. The dinosaurs had not yet taken control of the land environments as they did later.


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  1. Alcober, Oscar A.; Martinez, Ricardo N. (2010). "A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina". ZooKeys (63): 55–81. doi:10.3897/zookeys.63.550. PMC 3088398. PMID 21594020.
  2. Nesbitt S.J. et al 2009. (2009). "A complete skeleton of a late Triassic saurischian and the early evolution of dinosaurs". Science. 326 (5959): 1530–1533. Bibcode:2009Sci...326.1530N. doi:10.1126/science.1180350. PMID 20007898. S2CID 8349110.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  3. Airhart, Marc 2009. "New meat-eating dinosaur alters evolutionary tree". Jackson School of Geosciences. Archived from the original on 2011-10-02. Retrieved 2014-01-01.{{cite web}}: CS1 maint: numeric names: authors list (link)
  4. 4.0 4.1 Sereno P.C. and Novas F.E. 1992. The complete skull and skeleton of an early dinosaur. Science 258 (5085): 1137–1140.
  5. 5.0 5.1 5.2 Paul G.S. 1988 Predatory dinosaurs of the world (1989). Predatory Dinosaurs of the World: A Complete Illustrated Guide. New York: Simon and Schuster. pp. 248–250. ISBN 0-671-68733-6.{{cite book}}: CS1 maint: numeric names: authors list (link)
  6. 6.0 6.1 Langer, Max C. 2004. Basal Saurischia. In Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds) The Dinosauria. 2nd ed, Berkeley: University of California Press, pp. 25–46. ISBN 0-520-24209-2
  7. Tucker, Maurice E.; Benton, Michael J. (1982). "Triassic environments, climates and reptile evolution". Palaeogeography, Palaeoclimatology, Palaeoecology. 40 (4): 361–379. doi:10.1016/0031-0182(82)90034-7.
  8. Columbi, Carina E. 2008. Stable isotope analysis of fossil plants from the Upper Triassic Ischigualasto Formation in the northwest of Argentina. Houston, Texas: The Geological Society of America. Archived from the original on 2012-01-11. Retrieved 2014-01-01.{{cite conference}}: CS1 maint: numeric names: authors list (link)
  9. Sill, W D; Sill, W. D. (1974). "The anatomy of Saurosuchus galilei and the relationships of the rauisuchid thecodonts". Bulletin of the Museum of Comparative Zoology at Harvard College. 146: 317–362. ISSN 0027-4100.