Herrerasaurus

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Herrerasaurus
Temporal range: Upper Triassic
Mounted cast of skeleton, Senckenberg
Conservation status
Fossil
Scientific classification
Kingdom: Animalia
Class: Sauropsida
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda?
Family: Herrerasauridae
Genus: Herrerasaurus
Binomial name
Herrerasaurus ischigualastensis
Skeleton of Herrerasaurus and Eoraptor

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]

Description[change | edit source]

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]

Palaeoenvironment[change | edit source]

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

Herrerasaurus lived in these jungles alongside a smaller dinosaur, the one metre long Eoraptor, as well as Saurosuchus,[9] a huge quadrupedal Archosaur. 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.

References[change | edit source]

  1. Alcober, Oscar A.; and Martinez, Ricardo N. 2010. A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina. ZooKeys 63 (63): 55–81. doi:10.3897/zookeys.63.550. PMC 3088398. PMID 21594020.
  2. Nesbitt S.J. et al 2009 A complete skeleton of a late Triassic saurischian and the early evolution of dinosaurs. Science 326 (5959): 1530–1533. doi:10.1126/science.1180350. PMID 20007898.
  3. Airhart, Marc 2009. "New meat-eating dinosaur alters evolutionary tree". Jackson School of Geosciences. http://www.jsg.utexas.edu/news/rels/121009.html
  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. New York: Simon and Schuster. pp. 248–250. ISBN 0-671-68733-6.
  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. http://palaeo.gly.bris.ac.uk/benton/reprints/1982triassic.pdf. Retrieved 2009-07-23.
  8. Columbi, Carina E. 2008. Stable isotope analysis of fossil plants from the Upper Triassic Ischigualasto Formation in the northwest of Argentina. "{{{title}}}". Houston, Texas: The Geological Society of America. 
  9. Sill W.D. 1974 The anatomy of Saurosuchus galilei and the relationships of the rauisuchid thecodonts. Bulletin of the Museum of Comparative Zoology 146: 317–362.