- Eoraptor
Taxobox|
name = "Eoraptor"|
fossil_range = LateTriassic
image_width = 200px
regnum =Animal ia
phylum = Chordata
classis = Sauropsida
superordo =Dinosauria
ordo =Saurischia
subordo = ?Theropoda
genus = "Eoraptor"
species = "E. lunensis"
binomial = "Eoraptor lunensis"
binomial_authority = Sereno "et al.", 1993"Eoraptor" was one of the world's earliest
dinosaur s. It was a two-legged meat-eater that lived between 230 and 225million years ago , in what is now the northwestern region ofArgentina . Thetype species is "Eoraptor lunensis", which means 'dawn plunderer [from the Valley] of the Moon', denoting where it was originally discovered (Greek eos/εως meaning 'dawn' or 'morning' andLatin lunensis meaning 'of the moon').Paleontologist s believe the "Eoraptor" resembles the common ancestor of alldinosaur s. It is known from several well-preserved skeletons.Description and behavior
It had a thin body that grew to about 1
meter (3 ft) in length, with an estimated weight of about 10kilogram s (22 lb). It randigitigrade , upright on its hind legs. Its fore limbs were only half the length of its hind limbs and it had five digits on each 'hand'. Three of those digits, the longest of the five, ended in largeclaw s and were presumably used to handleprey . Scientists have surmised that the fourth and fifth digits were too tiny to be of any use in hunting."Eoraptor" probably ate mostly small
animal s. It was a swift sprinter and, upon catching its prey, it would use claws and teeth to tear the prey apart. However, it had both carnivore-type and herbivore-type teeth, so it could possibly have been omnivorous.Early dinosaur
The bones of this primitive dinosaur were first discovered in
1991 , byUniversity of Chicago paleontologistPaul Sereno , in the Ischigualasto Basin ofArgentina . During the LateTriassic Period, this was a river valley but is nowdesert badlands . "Eoraptor" was found in theIschigualasto Formation , the same formation that yielded "Herrerasaurus ", a very early theropod. By1993 it had been determined to be one of the earliestdinosaur s. Its age was determined by several factors, not least because it lacked the specialised features of any of the major groups of later dinosaurs, including its lack of specializedpredator y features. Unlike later carnivores, it lacked a sliding joint at the articulation of the lowerjaw , with which to hold large prey. Furthermore, only some of itsteeth were curved and saw-edged, unlike those in a later predator's mouth."Eoraptor" belonged to a major group of dinosaurs called
saurischia ns, or lizard-hipped dinosaurs. Their hip structures are similar to that of the modern lizard.The fact that it possessed some
herbivore teeth and five fully developed 'fingers' has led scientists to place "Eoraptor" at more ancient than even "Herrerasaurus". Only someprosauropod s, recently discovered inMadagascar , are thought to be older. There is a possibility that "Staurikosaurus " may be older, but it is rather large. "Staurikosaurus" seems to have features in common with both prosauropods and theropods, which has led scientists to question how primitive "Eoraptor" was in relation to other dinosaurs.External links
* [http://www.paulsereno.org Paul Sereno's Paleontology website]
* [http://paleodb.org/cgi-bin/bridge.pl?action=checkTaxonInfo&taxon_no=57453 Paleobiology Database entry]
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