Eodromaeus
Temporal range: Carnian
~231.4–229 Ma
Eodromaeus murphi.jpg
Restored skeleton
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Genus: Eodromaeus
Martinez et al. 2011
Species:
E. murphi
Binomial name
Eodromaeus murphi
Martinez et al. 2011

Eodromaeus (meaning "dawn runner") was a genus of basal theropod dinosaur known from the Late Triassic (Carnian) Valle de la Luna Member of the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.[1] It has been cited by Sereno as resembling a supposed common ancestor to all dinosaurs, the "Eve" of the dinosaurs.[2]

Etymology

Eodromaeus was named by Ricardo N. Martínez, Paul C. Sereno, Oscar A. Alcober, Carina E. Colombi, Paul R. Renne, Isabel P. Montañez and Brian S. Currie in 2011 and the type species is Eodromaeus murphi. The generic name is derived from the Greek words Eos ("Dawn", "Early") and Dromaeus ("Runner"). The specific name honors Jim Murphy, who used to work the area nearby where the fossils were found.[1]

Discovery

Artistic restoration

Fossils from Eodromaeus were first discovered in 1996 by Argentinean paleontologist Ricardo N. Martinez and Earthwatch volunteer Jim Murphy, and it was first believed that the fossils were a new species of Eoraptor. However, as the researchers started to take a closer look at the fossils, they found that it had many skeletal features which were absent in Eoraptor,[3] and they understood that it came from a new genus.

Eodromaeus is known from the holotype PVSJ 560, a nearly complete articulated skeleton recovered from the Valle de la Luna Member of the top of the Ischigualasto Formation, and the referred materials PVSJ 534, PVSJ 561, PVSJ 562 and PVSJ 877 from Valle de la Luna, La Peña and Cancha de Bochas Members of Ischigualasto, dating to the early Carnian faunal stage of the early Late Triassic, about 232–229 million years ago.[1]

Description

Size comparison between Eodromaeus and a human.

Eodromaeus was a relatively small dinosaur, with a total length of about 1.2 metres (3.9 ft) from nose to tail, and a weight of about 5 kilograms (11 lb). The trunk was long and slender. It is unknown how fast Eodromaeus could run, but it has been suggested to about 30 kilometres per hour (19 mph).[4] It is a basal carnivorous theropod. The forelimbs were much shorter than the hindlimbs, ending in hands with 5 digits. Digits IV and V (the ring finger and little finger in humans) were very reduced in size.[1]

Phylogeny

Restoration

Eodromaeus is regarded as one of the earliest members of Theropoda, the group that includes the carnivorous dinosaurs. The discovery of Eodromaeus lead some to believe that Eoraptor (typically regarded as a theropod) likely represented one of the most basal sauropodomorphs, the group that includes animals like Apatosaurus.[1] This has since been questioned however, with Bergman and Sues reclaiming Eoraptor as a theropod, like Eodromaeus.[5] This relationship was also recovered in the large analyses of early dinosaurs and other dinosauromorphs that were carried out by Baron, Norman and Barrett (2017).[6]

Cladogram after Martinez et al., 2011:[1]


Dinosauromorpha

Lagerpetonidae

Marasuchus

Silesauridae

Dinosauria

Ornithischia

Saurischia
Sauropodomorpha

Eoraptor

Panphagia

Saturnalia

Sauropodiformes

Theropoda

Herrerasaurus

Staurikosaurus

Eodromaeus

Neotheropoda

Coelophysoidea

Tawa

Dilophosaurus

"Syntarsus" kayentakatae

S. rhodesiensis

Coelophysis

References

  1. ^ a b c d e f Martínez et al., 2011
  2. ^ Bowdler N, "'Dawn runner casts light on birth of the dinosaurs", www.bbc.co.uk, 2011-01-13.
  3. ^ Choi T.Q., "Dinosaur Graveyard Reveals Oldest T. Rex Relative: Dawn Runner", www.FoxNews.com, 2011-01-13.
  4. ^ Weise E, "New dog-sized dinosaur discovered", www.usatoday.com, 2011-01-23.
  5. ^ Bergman D.S., Sues H-D. (2011), "A late-surviving basal theropod dinosaur from the latest Triassic of North America", Proceedings of the Royal Society B, published online 2011-04-13.
  6. ^ Baron, M.G., Norman, D.B., and Barrett, P.M. (2017). A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature, 543: 501–506. doi:10.1038/nature21700

Bibliography

  • Martínez, Ricardo N.; Paul C. Sereno; Oscar A. Alcober; Carina E. Colombi; Paul R. Renne; Isabel P. Montañez, and Brian S. Currie. 2011. A Basal Dinosaur from the Dawn of the Dinosaur Era in Southwestern Pangaea. Science 331. 206–210. Accessed 2019-03-29.

External links

  • Eodromaeus skeleton.
  • Eodromaeus skull.
  • Video: “Video: Fast, "Nasty" Little Dinosaur Discovered.” National Geographic January 13, 2011.