Cryolophosaurus ( or ; ) is a genus of large theropod dinosaur known from only a single species, Cryolophosaurus ellioti, from the Early Jurassic of Antarctica. It was one of the largest theropods of the Early Jurassic, with the subadult, being estimated to have reached long and weighed .

Cryolophosaurus was first excavated from Antarctica's Early Jurassic, Pliensbachian aged Hanson Formation, formerly the upper Falla Formation, by paleontologist Dr. William Hammer in 1991. It was the first carnivorous dinosaur to be discovered in Antarctica, and the first non-avian dinosaur from the continent to be officially named. The sediments in which its fossils were found have been dated to about 196 to 188 million years ago, representing the Early Jurassic Period.

Cryolophosaurus is known from a skull, a femur and other material, all of which have caused its classification to vary greatly. The femur possesses many primitive characteristics that have classified Cryolophosaurus as a dilophosaurid, or a neotheropod outside of Dilophosauridae and Averostra, whereas the skull has many advanced features, leading the genus to be considered a tetanuran, an abelisaurid, a ceratosaur and even an allosaurid. In 2016 Molina-Pérez and Larramendi gave a larger estimation of 7.7 meters (25.3 ft) and 780 kg (1,720 lb). Some researchers noted that the holotype individual probably represents a sub-adult, so adults could have been larger.

Skull

thumb|left|[[Life restoration]]

The holotype of C. ellioti consists of a high, narrow skull, which was discovered articulated with the rest of the skeleton. The crest is an extension of the skull bones, near the tear ducts, fused on either side to orbital horns, which rise from the eye sockets. While other theropods, like the Monolophosaurus have crests, they usually run along the skull instead of across it.

Classification

alt=holotype skull as preserved|right|thumb|The unrestored [[holotype skull, FMNH PR1821.]]

alt=|thumb|right|Fossil pelvis of Cryolophosaurus. The loop at the widest part of the pubis is large compared to later theropods.

Classification of Cryolophosaurus is difficult because it has a mix of primitive and advanced characteristics. In 2020, a monograph of Dilophosaurus found Cryolophosaurus to be a derived neotheropod, close to Averostra, in a more derived position than Zupaysaurus, but less than Dilophosaurus.

The following cladogram illustrates a synthesis of the relationships of the early theropod groups compiled by Hendrickx et al. in 2015.

right|upright|thumb|Restoration of a Cryolophosaurus in its environment|alt=

However, a 2020 study conducted by Adam Marsh and Timothy Rowe found C. ellioti to be a basal neotheropod. While it was still closer to Averostra than Coelophysoidea was, it was still more basal than Dilophosaurus.

Paleobiology

Cranial ornamentation

alt=|thumb|Reconstructed skull

Cranial display features, such as the one possessed by Cryolophosaurus, make sense in social, gregarious animals, where other members of the species are available to observe and interpret messages of sexual status. In the Early Jurassic, Antarctica was closer to the equator and the world was considerably warmer than today, but the climate was still cool temperate similar to that of modern southern Chile, and humid, with a temperature interval of 17–18 degrees. Models of Jurassic air flow indicate that coastal areas probably never dropped much below freezing, although more extreme conditions existed inland. a crow-sized pterosaur (a dimorphodontid), a tritylodont, herbivorous synapsid, and two small unnamed sauropodomorphs. Beyond vertebrates, Insects (Blattodea, Coleoptera), Ostracodans, Conchostracans and arthropod ichnofossils (Diplichnites, Planolites, Scoyenia) are known from other coeval localities, like Gair Mesa, Mount Carson or Shafer Peak. Plant remains are also very common, including large tree trunks (+50 cm) from Mount Carson to Palynomorphs at Shafer Peak. Macrofoliar and cuticle remains have also been recovered from several localities, including Conifers (Araucariaceae, Cheirolepidiaceae, Cupressaceae, Pinaceae or Voltziales), Cycadophytes (Bennettitales), Pteridosperms (Corystospermaceae), Ferns (Dipteridaceae, Matoniaceae, Osmundaceae and Polypodiales), Equisetaceae, Isoetaceae and Liverworts (Marchantiales). Some of the plant remains are relictual genera, like the youngest record of Dicroidium. Common presence of the invertebrate ichnogenus Planolites indicates the local fluvial, alluvial or lacustrine waters where likely continuous all year, as well the presence of abundant Otozamites trends to suggest high humidity.

</references>

  • Transantarctic Vertebrate Paleontology Project, official website for the NSF project conducting research on Cryolophosaurus and related fauna (photos, research information, publication list, geology, project members&nbsp;...)
  • Fryxell Geology Museum (photos, information)
  • Field Museum of Natural History (video, information)