Edmarka
Encyclopedia
Edmarka is a genus
of dinosaur
from the Late Jurassic
of North America
. The name honors scientist Bill Edmark. It was a theropod closely related to Torvosaurus
, and may, in fact, be a junior synonym
of that genus. Its fossils, including a partial skeleton, were found at Como Bluff
, Wyoming
.
The type species
, E. rex, was described in 1992 by Robert Bakker, Donald Kralis, James Siegwarth and James Filla. They distinguished their new species from Torvosaurus tanneri by features of the jugal
bone, which shows both primitive and derived features. The scapula-coracoid, ribs, and pubis were also described. Bakker et al. were impressed with the size of Edmarka, noting that it "would rival T. rex
in total length," and viewing this approximate size as "a natural ceiling for dinosaurian meat-eaters." Torvosaurine megalosaurs appear to occupy the top predator niche only in the lower and middle Morrison Formation
, and were replaced in the upper Morrison Formation by giant allosaurids. The presence of Torvosaurus and Edmarka in various Morrison Formation rocks upholds Dr. Robert T. Bakker's theory that there is only one large predator in a setting, and the presence of it prevents the evolution of any other.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. The name honors scientist Bill Edmark. It was a theropod closely related to Torvosaurus
Torvosaurus
Torvosaurus is a genus of large theropod dinosaur that lived during the Late Jurassic period...
, and may, in fact, be a junior synonym
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
of that genus. Its fossils, including a partial skeleton, were found at Como Bluff
Como Bluff
Como Bluff is a long ridge extending east-west, located between the towns of Rock River and Medicine Bow, Wyoming. The ridge is an anticline, formed as a result of compressional geological folding. Three geological formations, the Sundance, the Morrison, and the Cloverly Formations, containing...
, Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
.
The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, E. rex, was described in 1992 by Robert Bakker, Donald Kralis, James Siegwarth and James Filla. They distinguished their new species from Torvosaurus tanneri by features of the jugal
Jugal
The jugal is a skull bone found in most reptiles, amphibians, and birds. In mammals, the jugal is often called the malar or Zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species....
bone, which shows both primitive and derived features. The scapula-coracoid, ribs, and pubis were also described. Bakker et al. were impressed with the size of Edmarka, noting that it "would rival T. rex
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...
in total length," and viewing this approximate size as "a natural ceiling for dinosaurian meat-eaters." Torvosaurine megalosaurs appear to occupy the top predator niche only in the lower and middle Morrison Formation
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
, and were replaced in the upper Morrison Formation by giant allosaurids. The presence of Torvosaurus and Edmarka in various Morrison Formation rocks upholds Dr. Robert T. Bakker's theory that there is only one large predator in a setting, and the presence of it prevents the evolution of any other.
External links
- Edmarka in the Dinosaur Encyclopedia