Cryolophosaurus

Cryolophosaurus (/ˌkraɪoʊˌloʊfoʊˈsɔːrəs/ or /kraɪˌɒloʊfoʊˈsɔːrəs/; "CRY-oh-loaf-oh-SAWR-us") is a genus of large theropods known from only a single species Cryolophosaurus ellioti, known from the early Jurassic period of Antarctica. It was about 6.5 metres (21.3 ft) long and 465 kilograms (1,025 lb) in weight, making it one of the largest theropods of its time. Individuals of this species may have grown even larger, because the only known specimen probably represents a sub-adult. Cryolophosaurus is known from a skull, a femur and other material, the skull and femur 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, where as the skull has many advanced features, leading the genus to be considered a tetanuran, an abelisaurid, a ceratosaur and even an allosaurid. Since its original description, the consensus is that Cryolophosaurus is either a primitive member of the Tetanurae or a close relative of that group.

Cryolophosaurus possessed a distinctive "pompadour" crest that spanned the head from side to side. Based on evidence from related species and studies of bone texture, it is thought that this bizarre crest was used for intra-species recognition. The brain of Cryolophosaurus was also more primitive than those of other theropods.

Cryolophosaurus was first excavated from Antarctica's Early Jurassic, Sinemurian to 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 at ~194 to 188 million years ago, representing the Early Jurassic Period.

Cryolophosaurus
Temporal range:
Early Jurassic, 194–188 Ma
Reconstructed holotype skeleton
Reconstructed skeleton, Field Museum of Natural History
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Clade: Neotheropoda
Clade: Averostra
Clade: Tetanurae
Genus: Cryolophosaurus
Hammer & Hickerson, 1994
Type species
Cryolophosaurus ellioti
Hammer & Hickerson, 1994

Description

Cryolophosaurus reconstruction (flipped)
Cryolophosaurus restored with scales

The holotype FMNH PR1821 is the only fully described specimen of Cryolophosaurus. The specimen consists of an incomplete skull and mandibles lacking most of their front half; nine maxillary teeth; a fragmentary sixth cervical centrum; cervical vertebrae 7-10; several posterior cervical ribs; several anterior dorsal vertebrae; most mid and posterior dorsal vertebrae; several dorsal ribs; the fifth sacral vertebrae; three chevrons; many partial and complete caudal vertebrae and centra; two partial humeri; a proximal radius; a proximal ulna; a partial ilium; a proximal pubis; both ischia, but only one distal; two incomplete femora; the distal end of a tibia; the distal end of a fibula, and the astragalus and calcaneum.[1] In 2013, new material of Cryolophosaurus was unearthed in Antarctica. The description of this material has not yet been published in a non-abstract form.[2]

Cryolophosaurus Reflective Size Chart
Size Comparison with a human and Emperor penguin

Cryolophosaurus was a large, well-built theropod, one of the largest of its time. The genus has been described by Roger Benson and colleagues (2012) as a top predator in Antarctica. It had slender proportions.[3] Cryolophosaurus was estimated as being 6 to 7 m (19.7 to 23.0 ft) in length by William R. Hammer & William J. Hickerson (1999).[4] A 2007 study by Nathan Smith et al. revised the length to 6.5 m (21.3 ft).[1] Its weight estimated at 465 kilograms (1,025 lb).[1] Based on these length and weight estimates, Cryolophosaurus is currently the largest known Early Jurassic theropod.[3][5] Smith et al. (2007b) and Benson et al. (2012) noted that the holotype individual probably represents a sub-adult, so adults could have been larger.[1][3]

Cryolophosaurus ellioti 2
Cryolophosaurus restored with a speculative coat of feathers

Skull

Cryolophosaurus skull reconstruction FMNH
Close up of reconstructed skull
Cryolophosaurus braincase
Cryolophosaurus braincase (from the second specimen)

The holotype of Cryolophosaurus consists of a high, narrow skull, which was discovered articulated with the rest of the skeleton.[4] The skull is an estimated 65 centimetres (26 in) long. It has a peculiar nasal crest that runs just over the eyes, where it rises up perpendicular to the skull and fans out. It is thin and highly furrowed, giving it a unique "pompadour" appearance and earned it the nickname "Elvisaursus."[6] 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.[7]

An unpublished study conducted by Vernon Meidlinger-Chin in 2013 suggested that previous studies lacked focus on endocranial details. The study found that the Cryolophosaurus fossil has a nearly complete, undistorted cranial cavity which is complete enough to give an approximate shape and size of the living brain. The endocast features clarified the dissimilarity of the skull with those of Allosauroids and Coelurosaurs giving Cryolophosaurus a basal position in Theropoda.[5] Closer examination of how the skull bones fused together reviewed details in the snout and forehead that are especially similar to Dilophosaurus.[8]

Classification

Classification of Cryolophosaurus is difficult because it has a mix of primitive and advanced characteristics. The femur has traits of early theropods, while the skull resembles much later species of the clade Tetanurae, like China's Sinraptor and Yangchuanosaurus. This led Paul Sereno et al. (1994) to place Cryolophosaurus in the taxon Allosauridae.[9] Originally, Hammer and colleagues suspected that Cryolophosaurus might be a ceratosaur or even an early abelisaur, with some traits convergent with those of more advanced tetanurans, but ultimately concluded that it was itself the earliest known member of the tetanuran group.[10] While a subsequent study by Hammer (along with Smith and Currie) again recovered Cryolophosaurus as a tetanuran, a later (2007) study by the same authors found that it was more closely related to Dilophosaurus and Dracovenator.[7][11] Sterling Nesbitt et al. (2009), using the characters of Tawa found Cryolophosaurus to be a neither dilophosaurid nor averostran neotheropod but instead the sister group of a clade composed of dilophosaurids and averostrans.[12] However, in 2012, Matthew Carrano found that Cryolophosaurus was a tetanuran, related to Sinosaurus, but unrelated to Dilophosaurus.[13]

Cryolophosaurus Hip Fossil
Fossil pelvis of Cryolophosaurus. The loop at the widest part of the pubis is large compared to later theropods.

The following family tree illustrates a synthesis of the relationships of the early theropod groups compiled by Hendrickx et al. in 2015.[14]

Neotheropoda

Coelophysidae Coelophysis size flipped

Liliensternus

Zupaysaurus

Dilophosauridae Dilophosaurus wetherilli (flipped)

Averostra

Ceratosauria Ceratosaurus nasicornis DB

Tetanurae

Cryolophosaurus Cryolophosaurus reconstruction (flipped)

Sinosaurus

Monolophosaurus

Orionides

Megalosauroidea Spinosaurus by Joschua Knüppe

Avetheropoda

Allosauroidea Allosaurus Revised

Coelurosauria Utahraptor Restoration (flipped)

Discovery and naming

Cryolophosaurus Holotype Skull FMNH
The unrestored holotype of Cryolophosaurus, FMNH PR1821.

Cryolophosaurus originally was collected during the 1990–91 austral summer on Mount Kirkpatrick in the Beardmore Glacier region of the Transantarctic Mountains. The discovery was made by Hammer, a professor at Augustana College, and his team. The fossils were found in the siliceous siltstone of the Hanson Formation, formerly the upper Falla Formation, and dated to the Pliensbachian stage of the early Jurassic. Cryolophosaurus was the second dinosaur, and first theropod, to be discovered in Antarctica. It was discovered after Antarctopelta, but named earlier.[10]

Cryolophosaurus
Skeletal mount in front view

In 1991, both Hammer and the Ohio State University geologist David Elliot excavated separate outcroppings near Beardmore Glacier, sharing logistical expenses. Elliot's team first came across the remains of Cryolophosaurus in a rock formation around the altitude of 4,000 m (13,000 ft) high and about 640 km (400 mi) from the South Pole. When the discovery was made, they soon notified Hammer. Over the next three weeks, Hammer excavated 2,300 kg (5,100 lb) of fossil-bearing rock. The team recovered over 100 fossil bones, including those of Cryolophosaurus.[10] The specimens were formally named and described in 1994 by Hammer and Hickerson, in the journal Science.[10]

During the 2003 season, a field team returned and collected more material from the original site. A second locality was discovered about 30 metres (98 ft) higher in the section on Mt. Kirkpatrick.[15]

The name Cryolophosaurus ellioti is derived from the Greek words κρυος (meaning 'cold' or 'frozen', in reference to its discovery in Antarctica), λοφος (meaning 'crest') and σαυρος (meaning 'lizard'), thus "cold crest lizard". Hammer and Hickerson named the species C. ellioti, after David Elliot, who had made the initial discovery of the fossils.[10]

Paleobiology

Cranial ornamentation

Cryolophosaurus Frozen Crest Restoration
Restoration of the head crest

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.[16] Kevin Padian et al. (2004) challenged conventional hypotheses that the purpose of bizarre cranial structures and post-cranial armor in dinosaurs, was either for attracting mates, intimidating/fighting rivals in the group, or intimidating potential predators of other species. Padian et al. noted that based on phylogenetic, histological, and functional evidence these bizarre structures can be explained by the phenomenon of intra-species recognition, which is supported by the fossil evidence.[17][18] Thomas R. Holtz Jr. (2010) found that the bizarre crest of Cryolophosaurus was primarily for intra-species recognition, based on evidence from related species and studies of bone texture.[19] According to Thomas Rich and his colleagues, the crest would have been ineffective as a weapon and may have possibly functioned as a display feature during certain types of social behavior such as mating.[20] In 2019, a species recognition function was disputed but a socio-sexual display structure model was suggested.[21]

Diet

When the type specimen was discovered, several long cervical ribs, of a supposed prosauropod dinosaur were found in the mouth of Cryolophosaurus, which led Hammer (1998) to conclude that it was feeding on the prosauropod when it died. Hammer further noted that since the ribs were found extending all the way back to the theropod's neck region, this individual may have choked to death on these ribs.[4] However, Smith et al. concluded that these remains belonged to the Cryolophosaurus specimen itself, and not to Hammer's "prosauropod".[11] Hammer also concluded that a post-canine tooth belonging to a tritylodont (an early mammal relative), found with the remains, was part of its stomach contents when it died.[22]

Paleopathology

Juvenile Cryolophosaurus Teeth
Juvenile Cryolophosaurus teeth

Some Cryolophosaurus bones have pathologies that show evidence of scavenging. Broken teeth from a juvenile Cryolophosaurus were found nearby.[20] These teeth have no roots and likely shed naturally while scavenging the adult Cryolophosaurus carcass.

Cryolophosaurus Left Tibia Fossil
Cryolophosaurus left tibia (upper) and left tibia and fibula (lower) with calcaneum and astragalus

Another possible pathology is found in the astragalus (ankle bone) of Cryolophosaurus. This bone was preserved with a small splint from the fibula located just above the ankle. The splint, however, may also be just a unique morphological feature of Cryolophosaurus.[1]

Paleoecology

CryolophosaurusDB
Restoration of a Cryolophosaurus in its environment

All known specimens of Cryolophosaurus have been recovered in the Hanson Formation, which is one of only two major dinosaur-bearing rock formations found on the continent of Antarctica. It was discovered in "tuffaceous" siltstone deposited in the Sinemurian to Pliensbachian stage of the Early Jurassic,[4] approximately 194 to 188 million years ago.[2][23] This geological formation is part of the Victoria Group of the Transantarctic Mountains, which is approximately 4,000 metres (13,000 ft) above sea level.[4] The high altitude of this site supports the idea that early Jurassic Antarctica had forests populated by a diverse range of species, at least along the coast.[24][25] The Hanson Formation was deposited in an active volcano−tectonic rift system formed during the breakup of Gondwana.[11]

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.[26] Models of Jurassic air flow indicate that coastal areas probably never dropped much below freezing, although more extreme conditions existed inland.[27] Cryolophosaurus was found about 650 kilometres (400 mi) from the South Pole but,[4] at the time it lived, this was about 1,000 km (621 mi) or so farther north.[24] This formation has produced the remains of Glacialisaurus[28] (a large basal sauropodomorph), a crow-sized pterosaur (a dimorphodontid), a synapsid (a tritylodont, which is a type of synapsid about the size of a rat), herbivorous synapsid, and two small unnamed sauropodmorphs.[10] There are also the remains of many plant genera recovered from the Early Jurassic Camp Hill Formation, around the same age as fossils of Cryolophosaurus, proving that dense plant matter had once grown on Antarctica's surface before it drifted southward.[29]

References

  1. ^ a b c d e Smith, N.D.; Makovicky, P.J.; Hammer, W.R.; Currie, P.J. (2007). "Osteology of Cryolophosaurus ellioti (Dinosauria: Theropoda) from the Early Jurassic of Antarctica and implications for early theropod evolution" (PDF). Zoological Journal of the Linnean Society. 151 (2): 377–421. doi:10.1111/j.1096-3642.2007.00325.x.
  2. ^ a b Smith, N.D.; Hammer, W.R.; Makovicky, P.J. (2013). "New Dinosaurs from the Early Jurassic Hanson Formation of Antarctica, and Patterns of Diversity and Biogeography in Early Jurassic Sauropodomorphs". Geological Society of America Abstracts with Programs: 405–406.
  3. ^ a b c Benson, R.; Brusatte, S.; Hone, D.; Naish, D.; Xu, X.; Anderson, J.; Clack, J.; Duffin, C.; Milner, A.; Parsons, K.; Prothero, D.; Johanson, Z.; Dennis-Bryan, K. (2012) [2009]. Ambrose, Jamie; Gilpin, David; Hirani, Salima; Jackson, Tom; Joyce, Nathan; Maiklem, Lara; Marriott, Emma; Nottage, Claire; van Zyl, Meizan (eds.). Prehistoric Life: A Definitive Visual History of Life on Earth. Dorling Kindersley. pp. 1–512. ISBN 978-0-7566-9910-9. OCLC 444710202.
  4. ^ a b c d e f Hammer, W.R.; Hickerson, W.J. (1999). Tomida, Y.; Rich, T.H.; Vickers-Rich, Y. (eds.). "Gondwana Dinosaurs from the Jurassic of Antarctica". Proceedings of the Second Gondwana Dinosaur Symposium National Science Museum Monographs. 15: 211–217.CS1 maint: Uses editors parameter (link)
  5. ^ a b Meidlinger-Chin, V. (2013). "Braincase and Endocranial anatomy of Cryolophosaurus ellioti (Dinosauria: Theropoda) from the Early Jurassic of Antarctica". Geological Society of America Abstracts with Programs. 45 (4): 65.
  6. ^ swigodner (2017-08-02). "Antarctic Dinosaurs". Field Museum. Retrieved 2018-12-31.
  7. ^ a b Smith, N. D.; Hammer, W.R.; Currie, P.J. (2005). "Osteology and phylogenetic relationships of Cryolophosaurus ellioti (Dinosauria: Theropoda): Implications for basal theropod evolution". Journal of Vertebrate Paleontology. 25 (3): 116A–117A. doi:10.1080/02724634.2005.10009942.
  8. ^ "VERTEBRAL ANATOMY OF CRYOLOPHOSAURUS ELLIOTI, A THEROPOD DINOSAUR FROM THE EARLY JURASSIC OF ANTARCTICA". gsa.confex.com. Retrieved 2018-12-31.
  9. ^ Sereno, P.C.; Wilson, J.A.; Larsson, H.C.E.; Dutheil, D.B.; Sues, H-D. (1994). "Early Cretaceous dinosaurs from the Sahara". Science. 266 (5183): 267–270. doi:10.1126/science.266.5183.267. PMID 17771449.
  10. ^ a b c d e f Hammer, W. R.; Hickerson, W. J. (1994). "A Crested Theropod Dinosaur from Antarctica". Science. 264 (5160): 828–830. doi:10.1126/science.264.5160.828. PMID 17794724.
  11. ^ a b c Smith, N. D.; Makovicky, P.J.; Pol, D.; Hammer, W.R.; Currie, P.J. (2007). "The Dinosaurs of the Early Jurassic Hanson Formation of the Central Transantarctic Mountains: Phylogenetic Review and Synthesis". US Geological Survey Open-File Report. 2007 (1047srp003). doi:10.3133/of2007-1047.srp003.
  12. ^ Nesbitt, S.J.; Smith, N.D.; Irmis, R.B.; Turner, A.H.; Downs, A.; Norell, M.A. (2009). "A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs". Science. 326 (5959): 1530–1533. doi:10.1126/science.1180350. PMID 20007898.
  13. ^ Carrano, M. T.; Benson, R. B. J.; Sampson, S. D. (2012). "The phylogeny of Tetanurae (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 10 (2): 211–300. doi:10.1080/14772019.2011.630927.
  14. ^ Hendrickx, C.; Hartman, S.A.; Mateus, O. (2015). "An Overview of Non- Avian Theropod Discoveries and Classification". PalArch's Journal of Vertebrate Palaeontology. 12 (1): 1–73.
  15. ^ Leslie, M (2007). "The Strange Lives of Polar Dinosaurs". Smithsonian Magazine. Archived from the original on 2012-07-02. Retrieved 2008-01-24.
  16. ^ Dodson, P. (1997). "Paleoecology". In Currie, P.J.; Padian, K. (eds.). Encyclopedia of Dinosaurs. Academic Press. ISBN 978-0-12-226810-6.
  17. ^ Glut, D.F. (2006). Dinosaurs, the Encyclopedia, Supplement 4. McFarland & Company, Inc. p. 749. ISBN 978-0-7864-2295-1.
  18. ^ Padian, K.; Horner, J.R.; Dhaliwal, J. (2004). "Species recognition as the principal cause of bizarre structures in dinosaurs". Journal of Vertebrate Paleontology. 23 (3 Suppl): 100A. doi:10.1080/02724634.2003.10010538.
  19. ^ Holtz, T.R. Jr. (2012). Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages (PDF). Random House Books for Young Readers. pp. 90–91. ISBN 978-0-375-82419-7.
  20. ^ a b Rich, T.R.; Gangloff, R.A.; Hammer, W.R. (1997). "Polar dinosaurs". In Currie, P.J.; Padian, K. (eds.). Encyclopedia of Dinosaurs. Academic Press. pp. 562–573. ISBN 978-0-12-226810-6.
  21. ^ Cite error: The named reference Yun2019 was invoked but never defined (see the help page).
  22. ^ Glut, D.F. (1999). Dinosaurs, the Encyclopedia, Supplement 1. McFarland & Company, Inc. p. 442. ISBN 978-0-7864-0591-6.
  23. ^ Evans, D.C.; Vavrek, M.J. (2012). Ultimate Dinosaurs: Giants from Gondwana. Toronto:Royal Ontario Museum. pp. 30–1.
  24. ^ a b Dodson, P. (1997). "Distribution and Diversity". In Currie, P.J.; Padian, K. (eds.). Encyclopedia of Dinosaurs. Academic Press. pp. 10–13. ISBN 978-0-12-226810-6.
  25. ^ Holtz, T.R. Jr.; Molnar, R.E.; Currie, P.J. (2004). "Basal Tetanurae". In Weishampel, D.B.; Dodson, P.; Osmólska, H. (eds.). The Dinosauria (Second ed.). University of California Press. pp. 71–110. ISBN 978-0-520-24209-8.
  26. ^ Pickrell, John (2004). "Two New Dinosaurs Discovered in Antarctica". National Geographic. Retrieved 20 December 2013.
  27. ^ Chandler, M. A.; Rind, D.; Ruedy, R. (1992). "Pangaean climate during the Early Jurassic: GCM simulations and the sedimentary record of paleoclimate". Geological Society of America Bulletin. 104 (5): 543. doi:10.1130/0016-7606(1992)104<0543:PCDTEJ>2.3.CO;2.
  28. ^ Smith, Nathan D.; Pol, Diego (2007). "Anatomy of a basal sauropodomorph dinosaur from the Early Jurassic Hanson Formation of Antarctica" (pdf). Acta Palaeontologica Polonica. 52 (4): 657–674.
  29. ^ Rees, P.M. & Cleal, C.J. (2004). "Lower Jurassic floras from Hope Bay and Botany Bay, Antarctica" (PDF). Special Papers in Palaeontology. 72: 5–90. Archived from the original (PDF) on 2010-07-22.CS1 maint: Uses authors parameter (link)

[1]

External links

  1. ^ Template:Title=Chan-gyu Yun. 2019. An enigmatic theropod Cryolophosaurus: Reviews and Comments on its paleobiology. Volumina Jurassica 17: 1-8.
Averostra

Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.

Avetheropoda

Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.

Cerapoda

Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.

Dilophosauridae

Dilophosauridae is a family of medium to large sized theropod dinosaurs. The name Dilophosauridae is derived from Greek, with “di” meaning “two,” “lophos” meaning “crest,” “sauros” meaning “lizard,” and “idae” meaning “family”. While the name suggests that all dilophosaurids have two crests, this is not applicable to all dilophosaurids. The Dilophosauridae is anchored by the genus Dilophosaurus, and therefore the name comes from the distinctive two crests of the genus.

Dinosaur Revolution

Dinosaur Revolution is a four-part American nature documentary produced by Creative Differences. It utilizes computer-generated imagery to portray dinosaurs and other animals from the Mesozoic era. The program was originally aired on the Discovery Channel and Science.

Dinosaur Revolution was released to mixed reviews, with some citing the quality of its animation and a lack of seriousness in its tone as reasons for criticism. It was, however, praised for its educational content and general energy.

Dinosaur Train

Dinosaur Train is an American/Canadian/Singaporean children's animated series created by Craig Bartlett, who also created Hey Arnold! and Ready Jet Go!. The series features a curious young Tyrannosaurus rex named Buddy who, together with his adopted Pteranodon family, takes the Dinosaur Train to explore his time period, and have adventures with all kinds of dinosaurs. It is produced by The Jim Henson Company in association with Media Development Authority, Sparky Animation, FableVision, and Snee-Oosh, Inc. As of 2018, PBS Kids had ordered 11 more episodes, taking the total number of episodes to 100.

Dinosauriformes

Dinosauriformes is a clade of archosaurian reptiles that include the dinosaurs and their most immediate relatives. All dinosauriformes are distinguished by several features, such as shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs. The oldest known member is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.

Jeholosauridae

Jeholosaurids were herbivorous neornithischian dinosaurs from the Cretaceous Period (Aptian - Santonian, with a possible Campanian record) of Asia. The family was first proposed by Han et al. in 2012. The jeholosaurids were defined as those ornithischians more closely related to Jeholosaurus shangyuanensis than to Hypsilophodon foxii, Iguanodon bernissartensis, Protoceratops andrewsi, Pachycephalosaurus wyomingensis, or Thescelosaurus neglectus. The Jeholosauridae includes the type genus Jeholosaurus and Yueosaurus.

Jingshanosaurus

Jingshanosaurus (meaning "Jingshan lizard") is a genus of sauropodomorph dinosaurs from the early Jurassic period.

Lepidus praecisio

Lepidus is a genus of extinct coelophysoidean theropod from the Upper Triassic of the United States. It lived in the Otis Chalk localities of the Dockum Group in Texas, around 223 million years ago.

Melanorosauridae

The Melanorosauridae were a family of sauropodomorph dinosaurs which lived during the Late Triassic and Early Jurassic. The name Melanorosauridae was first coined by Friedrich von Huene in 1929. Huene assigned several families of dinosaurs to the infraorder "Prosauropoda": the Anchisauridae, the Plateosauridae, the Thecodontosauridae, and the Melanorosauridae. Since then, these families have undergone numerous revisions. Galton and Upchurch (2004) considered Camelotia, Lessemsaurus, and Melanorosaurus members of the family Melanorosauridae. A more recent study by Yates (2007) indicates that the melanorosaurids were instead early sauropods.

Monolophosaurus

Monolophosaurus ( MON-o-LOF-ə-SAWR-əs; meaning "single-crested lizard") is a genus of tetanuran theropod dinosaur from the Middle Jurassic Shishugou Formation in what is now Xinjiang, China. It was named for the single crest on top of its skull. Monolophosaurus was a mid sized theropod at about 5 metres long.

Neotheropoda

Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.

Orionides

Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.

Riojasauridae

Riojasauridae is a family of sauropod-like dinosaurs from the Upper Triassic. It is known primarily from the genera Riojasaurus and Eucnemesaurus. Sites containing Riojasauridae include the Lower Elliot Formation of Orange Free State, South Africa (where fossils of Eucnemesaurus have been found), and Ischigualasto, in La Rioja Province, Argentina ( where fossils of Riojasaurus have been recovered).

Sinosaurus

Sinosaurus (meaning "Chinese lizard") was a tetanuran theropod dinosaur which lived during the Early Jurassic Period. It was a bipedal carnivore approximately 5.6 metres (18 feet) in length. Fossils of the animal were found at the Lufeng Formation, in the Yunnan Province of China.

Tetanurae

Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, tyrannosauroids, ornithomimosaurs, maniraptorans, and birds. Tetanurans are defined as all theropods more closely related to modern birds than to Ceratosaurus and contain the majority of predatory dinosaur diversity. Tetanurae likely diverged from its sister group, Ceratosauria, during the late Triassic. Tetanurae first appeared in the fossil record by the Early Jurassic about 190 mya and by the Middle Jurassic had become globally distributed.The group was named by Jacques Gauthier in 1986 and originally had two main subgroups: Carnosauria and Coelurosauria, the clade containing birds and related dinosaurs such as compsognathids, tyrannosaurids, ornithomimosaurs, and maniraptorans. The original Carnosauria was a polyphyletic group including any large carnivorous theropod. Many of Gauthier's carnosaurs, such as tyrannosaurids, have since been re-classified as coelurosaurs or primitive tetanurans. Carnosauria has been reclassified as a group containing allosaurids that split from the Coelurosauria at the Neotetanurae/Avetheropoda node. Members of Spinosauroidea are believed to represent basal tetanurans.Tetanuran evolution was characterized by parallel diversification of multiple lineages, repeatedly attaining large body size and similar locomotor morphology. Cryolophosaurus has been claimed as the first true member of the group, but subsequent studies have disagreed on whether it is a dilophosaurid or tetanuran. Arcucci and Coria (2003) classified Zupaysaurus as an early tetanuran, but it was later placed as a sister taxon to the clade containing dilophosaurids, ceratosaurs, and tetanurans.Shared tetanuran features include a ribcage indicating a sophisticated air-sac-ventilated lung system similar to that in modern birds. This character would have been accompanied by an advanced circulatory system. Other tetanuran characterizing features include the absence of the fourth digit of the hand, placement of the maxillary teeth anterior to the orbit, a strap-like scapula, maxillary fenestrae, and stiffened tails. During the Late Jurassic and Early Cretaceous, large spinosaurids and allosaurs flourished but possibly died out in the northern hemisphere before the end of the Cretaceous, and were replaced as apex predators by tyrannosauroid coelurosaurs. At least in South America, carcharodontosaurid allosaurs persisted until the end of the Mesozoic Era, and died out at the same time the non-avian coelurosaurs.

William R. Hammer

William Roy Hammer is an American paleontologist who is credited with the discovery of the first carnivorous dinosaur unearthed in Antarctica, Cryolophosaurus, in 1991. He was professor of geology and curator of the Frxyell Geology Museum at Augustana College in Rock Island, IL from 1981-2017.

Zupaysaurus

Zupaysaurus (; "ZOO-pay-SAWR-us") is a genus of early theropod dinosaur living during the Norian stage of the Late Triassic in what is now Argentina. Fossils of the dinosaur were found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. Although a full skeleton has not yet been discovered, Zupaysaurus can be considered a bipedal predator, up to 4 metres (13 ft) long. It may have had two parallel crests running the length of its snout.

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