Eodromaeus murphi
- 演化之聲
- 5 days ago
- 2 min read
Age
Triassic（Carnian）
230 Ma
Taxonomy
Kingdom：Animalia
Phylum：Chordata
Class：Reptilia
Order：Saurischia
Genus：Eodromaeus
Species：Eodromaeus murphi
Morphological description
Eodromaeus murphi was a small dinosaur estimated to have reached approximately 1.2 metres in length and weighed between 4.5 and 7.1 kilograms. It possessed a lightly built body and relatively long hindlimbs, suggesting it was well adapted for running.
The skull of Eodromaeus was roughly rectangular in shape and measured about 12 centimetres in length. Its antorbital fenestra was large, and the jaws contained around 15 blade-like teeth, with the longest teeth located in the anterior half of the maxilla. The lower jaw was slender and the teeth were widely spaced. In addition, the pterygoid bone of the palate bore a row of small palatal teeth, a feature that is extremely rare among dinosaurs.
Compared with Eoraptor, Eodromaeus possessed longer cervical vertebrae. The posterior cervical vertebrae contained large depressions that may have housed air sacs. Its dorsal vertebrae were relatively short but numerous, while the tail vertebrae were connected by elongated articular processes. The forelimbs retained five fingers, although the fourth and fifth digits were highly reduced.
Etymology
The genus name Eodromaeus combines the Greek Eos (“dawn” or “early”) and dromaeus (“runner”).
The species name honours Jim Murphy.
Biological interpretation
Fossils of Eodromaeus were first discovered in 1996 from the Ischigualasto Formation of San Juan Province, Argentina. Initially, the material was considered to represent a new species of Eoraptor. However, later studies identified numerous skeletal characteristics absent in Eoraptor, leading to the formal naming of Eodromaeus murphi as a new genus and species in 2011.
To date, six specimens of Eodromaeus have been discovered from different stratigraphic levels of the Ischigualasto Formation. The most complete specimen is the holotype PVSJ 560, which, despite being fragmented, preserves most of the skeleton.
In its original description, Eodromaeus murphi was interpreted as a basal member of Theropoda, with only Herrerasauridae considered more primitive. However, subsequent studies have frequently revised its phylogenetic position, and its exact classification remains controversial.
（Author: Bai Leng）
Reference
1. Martínez, R. N., Sereno, P. C., Alcober, O. A., Colombi, C. E., Renne, P. R., Montañez, I. P., Currie, B. S. ( 2011). A Basal Dinosaur from the Dawn of the Dinosaur Era in Southwestern Pangaea. Science.
2. Weise E. New dog-sized dinosaur discovered. www.usatoday.com. 2011-01-23.
3. Benson, R. B. J., Hunt, G., Carrano, M. T., Campione, N. (2018). Cope's rule and the adaptive landscape of dinosaur body size evolution. Palaeontology.
4. Kubo, T., Kubo, M. O. (2012). Associated evolution of bipedality and cursoriality among Triassic archosaurs: a phylogenetically controlled evaluation. Paleobiology.
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