Cryolophosaurus
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| Cryolophosaurus ellioti Hammer & Hickerson, 1994 |
Cryolophosaurus (/kɹaɪ.əʊ'ləʊf.əʊ'sʊə.ʌs/ or /ˌkɹaɪəʊˈlɒfəsɔɹəs/, meaning "cold crest lizard") was a large bipedal dinosaur, with a bizarre crest on its head that looked like a Spanish comb. Due to the resemblance to Elvis Presley's pompadour haircut in the 1950s, the dinosaur was at one point informally known as the Elvisaurus.
Cryolophosaurus was discovered in Antarctica's Falla Formation by paleontologist Dr. William Hammer in 1991. It is the first carnivorous dinosaur to be discovered in Antarctica and the first dinosaur of any kind from the continent to be officially named. Dating from the Early Jurassic Period, it is also the earliest tetanuran theropod yet discovered.
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[edit] Description
Cryolophosaurus was about 6 to 8 meters (20 to 26 feet) long, which is significantly smaller than the largest Allosaurus, which reached up to 12 meters (40 feet) in length.
A high, narrow skull was discovered, 65 centimeters (25 inches) long. The peculiar nasal crest runs just over the eyes, where it rises up, perpendicular to the skull and fans out. It is furrowed, giving it a comb-like appearance. It is an extension of the skull bones, near the tear ducts, fused on either side to horns which rise from the eye sockets (orbital horns). While other theropods like the Monolophosaurus have crests, they usually run along the skull instead of across it.
The crest is too fragile to be used in combat, so it was probably used in mating displays.
[edit] Forests of the night
The remains of the Cryolophosaurus were found in the Hanson Formation with the remains of a very large prosauropod (related to plateosaurids like the Plateosaurus and Lufengosaurus), a small pterosaur, a mammal-like reptile (a tritylodont, which is a type of synapsid about the size of a rat), and another unknown theropod. There were also fossilized tree trunks two meters away. The site is about 4,000 meters (13,000 feet) above sea level. During the early Jurassic it was a river bed on the southern coast of the supercontinent of Gondwana.
This supports the idea that, even at high altitudes, early Jurassic Antarctica had forests populated by a diverse range of species, at least along the coast. Even though Antarctica was closer to the equator and the world was considerably warmer than today, the climate was still cool temperate. Recent models of Jurassic air flow indicate that coastal areas probably never dropped much below freezing, although more extreme conditions existed inland. This suggests that dinosaurs could endure relatively cool environments and even possibly survive snow.
Cryolophosaurus was found about 650 kilometers (400 miles) from the South Pole but, at the time it lived, this was about 1000km or so farther north. Cryolophosaurus, therefore, did not have to contend with the polar night.
The specimen was found in conjunction with a platter from the prosauropod which has led to speculation that it may have choked to death, although there is no concrete evidence of this one way or the other.
[edit] Classification
- "Cryolophosaurus is also of significance because it represents the oldest known tetanuran from any continent — it is the only one from the Early Jurassic."
- —William R. Hammer
Classification is difficult because the Cryolophosaurus has a mix of primitive and advanced characteristics. The leg bone (femur) has traits of early theropods, while the skull resembles much later species, like China's Sinraptor and Yangchuanosaurus. Originally, it was suspected that Cryolophosaurus might be a ceratosaur or even an early abelisaur, with some traits convergent with those of more advanced tetanurans. Mortimer ([1]) added Cryolophosaurus to the data from a study by Rauhut (2000) and found it to be even more primitive - a coelophysoid closely related to Dilophosaurus. This animal gives fuel to the argument that tetanuran Carnosaurs, like the Allosaurs, share a common ancestor and are closer than previously believed to the more "primitive" Ceratosaurus and its kin and that Cryolophosaurus could be the ancestor or close to the ancestor of both groups, accounting for the mixture of advanced and primitive characteristics. However, it is still believed by most researchers to be an early and primitive tetanuran. The most recent study that included Cryolophosaurus, Smith et al. (2005), recovered this position.
[edit] Discovery
Cryolophosaurus was discovered in 1991, by William R. Hammer and his team, on Mount Kirkpatrick, the highest peak in the Queen Alexandra Range of the Transantarctic Mountains and additional remains were excavated during a second expedition in 2003. They were located in the siltstone of the Hanson Formation and dated to the Pliensbachian age of the early Jurassic.
It was formally named and described in 1994 by William R. Hammer and William J. Hickerson, in the journal Science. The name Cryolophosaurus was dervived from the Greek κρυος (meaning 'cold' or 'frozen'), λοφος (meaning 'crest') and σαυρος (meaning 'lizard'). The name refers not the extreme conditions faced by the excavation team but to the relatively cool climate that the dinosaur lived in.
The remains include part of a skull (cranium), a jaw bone (mandible), parts of the backbone (30 vertebrae), hip bones (the illum, ischium, and pubis), leg bones (femur and fibula), an ankle bone (tibiotarsus) and foot bones (metatarsals). The skull was partially crushed by the Beardmore Glacier, but the crushed front portion of the skull has been reconstructed. At least the skull and jaw bone and the foot bones, were found in their natural positions (articulated).
The 2003 expedition uncovered additional Cryolophosaurus remains, which are awaiting preparation, and a possible skin impression.
Hammer is a professor of geology and paleontology at Augustana College in Rock Island, Illinois and a curator at the Fryxell Geology Museum, where the holotype specimen currently resides. As of Summer 2006, he is planning a 2008 expedition to Antarctica.
[edit] References
- Hammer, W.R., and W. J. Hickerson (1994). "A crested theropod dinosaur from Antarctica." Science, 264(5160): 828-830. May 6, 1994. (abstract)
- Smith, Hammer, and Currie (2005). "Osteology and phylogenetic relationships of Cryolophosaurus ellioti (Dinosauria: Theropoda): Implications for basal theropod evolution." Journal of Vertebrate Paleontology, 25(3): 116A-117A.
[edit] External links
- Fryxell Geology Museum, by Steve Brusatte from Dino Land Travels Photo Database. (photos, interviews)
- Cryolophosaurus, by T. Mike Keesey from the Dinosauricon. (cladogram)
- Cryolophosaurus elliotti from Prehistorics Illustrated. (art)
- First Antarctic dinosaur fossils shed light on Earth's past, by William Mullen from the Chicago Tribune (via The Kansas City Star). February 4, 2004. (second expedition)
