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EORAPTOR

a possible guaibasaurid sauropodomorph dinosaur from the Late Triassic of Argentina.
eoraptor.png
Pronunciation: EE-oh-RAP-tor
Meaning: Dawn plunderer
Author/s: Sereno, et al. (1993)
Synonyms: None known
First Discovery: San Juan, Argentina
Chart Position: 307

Eoraptor lunensis

Eoraptor is one of the earliest true dinosaurs, and upon discovery by Ricardo N. Martinez in the Ischigualasto Badlands of Argentina way back in 1991 Paul Sereno thought it was the earliest known theropod. And why wouldn't he? The bipedal stance, an extra vertebra at the hip and a long tail for counter balance, was a design blueprint for future theropods. Plus, a percentage of sharp meat-slicing teeth, specialized forearms and three functional, clawed fingers (flanked by two small unclawed ones) appear to be adaptations for a predatory lifestyle. However, a percentage of plant-grinding teeth, large nostrils, and a lower jaw that lacked the necessary articulation to hold large prey had always been a cause for concern. And things came to a head in 2011 when the placement of Eoraptor was challenged, by a specimen of itself, no less.

Restudy of a skeleton that was discovered in 1996 and assigned to Eoraptor turned out to be an all new critter that Martinez named Eodromaeus—Dawn Runner. In one fell swoop, it took up squatters rights in the "small primitive theropod closer to Tawa than to Herrerasaurus" niche and booted Eoraptor out of theropoda and into sauropodomorpha, possibly as a guaibasaurid—the small, bipedal sauropodomorphs that may have been omnivorous.

This is about as big a leap as any dinosaur has ever made and understandably it's too much for some paleontologists to fathom. It may be that Eoraptor is the earliest known saurischian and the ancestor of all dinosaurs, straddling the junction that led to Theropoda and Sauropodomorpha, but research is ongoing and there are still many questions that remain unanswered.
Discovery
The first fossils of Eoraptor were discovered close to the the same site as Herrerasaurus at "Valle de la Luna" in the Ischigualasto Formation, Ischigualasto Badlands, San Juan, northwestern Argentina (which was a river valley during the late Triassic) by University of San Juan paleontologist Ricardo Martínez in 1991.
The holotype (PVSJ 512) is a partial skeleton.
Estimations
Timeline:
Era: Mesozoic
Epoch: Triassic
Stage: Carnian
Age range: 237-228 mya
Stats:
Est. max. length: 1 meters
Est. max. hip height: 0.3 meters
Est. max. weight: 12 Kg
Diet: Omnivore
Family Tree:
Dinosauria
Saurischia
Sauropodomorpha
Guaibasauridae?
Eoraptor
lunensis
References
• Sereno PC, Forster, Rogers and Monetta (1993) "Primitive dinosaur skeleton from Argentina and the early evolution of Dinosauria". Nature 361, 64 - 66 (07 January 1993); doi:10.1038/361064a0
• DigiMorph Staff (2001) "Eoraptor lunensis: Primitive Dinosaur". Digital Morphology, The University of Texas at Austin. http://digimorph.org/specimens/Eoraptor_lunensis/.
• Martinez RN, Sereno PC, Alcober OA, Colombi CE, Renne PR, Montañez IP and Currie BS (2011) "A Basal Dinosaur from the Dawn of the Dinosaur Era in Southwestern Pangaea". Science 331: 206-210.
• Sereno PC, Martínez RN and Alcober OA (2012) "Osteology of Eoraptor lunensis (Dinosauria, Sauropodomorpha)". Journal of Vertebrate Paleontology 32:83-179.
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To cite this page:
Atkinson, L. "EORAPTOR :: from DinoChecker's dinosaur archive".
›. Web access: 24th Nov 2017.
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