Dilophosauridae

Dilophosauridae is a family of medium to large sized theropod dinosaurs.[2] The name Dilophosauridae is derived from Greek, with “di” meaning “two,” “lophos” meaning “crest,” “sauros” meaning “lizard,” and “idae” meaning “family”.[3] 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.

Dilophosaurids
Temporal range: Late Triassic - Early Jurassic, 200–188 Ma
DilophosaurusROM1
Reconstructed cast of the holotype specimen of Dilophosaurus (UCMP 37302) in burial position, Royal Ontario Museum
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Clade: Neotheropoda
Family: Dilophosauridae
Madsen & Welles, 2000
Genera[1]

Description

Dilophosaurids were large bipedal predators with lengths of 4 to 7 metres and estimated adult weights of 300 to 500 kg. They are well known for their distinctive head crests, which were probably used for mating displays, or to intimidate rivals.[4]

All dilophosaurids are characterized by a hole in the premaxilla, few maxillary teeth, a slot-shaped opening at the base of the nasal process of the premaxilla, nasolacrimal crests, and a number of dorsal tab-like bumps on the articular, which is located on the back end of the lower jaw.[5]

Body size

Dilophosaurus had an average femur length of 552 mm, body lengths of 6 to 7 meters, and body masses of 362 kg.[6] The dilophosaurid Dracovenator had a body length of approximately 5.5 to 7.0 meters long.[4]

Due to a lack of endemism of Dilophosauridae, body size has been used to weakly classify taxa to Dilophosauridae. Dilophosaurus and Dracovenator are both genera of similar body length, estimated to be around 6–7 meters in length, providing some support for these two taxa as belonging to the same family.[7]

Classification

The family Dilophosauridae was proposed by Alan Charig and Andrew Milner in 1990 to contain only the type genus, Dilophosaurus.[8] Other genera, such as Zupaysaurus and Dracovenator, have since been assigned to this family, though the group has never been given a phylogenetic definition and is not currently a clade. Some studies have suggested that there was a natural group of medium-sized crested theropods which included Dilophosaurus as well as Dracovenator, Cryolophosaurus, and Sinosaurus, though it has not been formally named Dilophosauridae.[9] While traditionally assigned to the superfamily Coelophysoidea, these analyses suggest that dilophosaurids may have been more closely related to the group Tetanurae, comprising the more advanced megalosaurs, carnosaurs and coelurosaurs.

The following cladogram outlines the relationships of Dilophosaurus and its close relatives as recovered by the 2007 analysis of Smith, Makovicky, Pol, Hammer, and Currie.[9]

Neotheropoda

Coelophysoidea Coelophysis size flipped

Averostra

Zupaysaurus

unnamed
Dilophosauridae

Sinosaurus (="Dilophosaurus" sinensis)

unnamed

Dracovenator

unnamed

Dilophosaurus Dilophosaurus wetherilli (flipped)

Cryolophosaurus Cryolophosaurus reconstruction (flipped)

Neoceratosauria Ceratosaurus nasicornis DB

Tetanurae Austroraptor Restoration (flipped)

In 2015, Hendrickx et al. proposed a family tree that reflects a more restricted view of the family Dilophosauridae. Although Dilophosauridae previously included Dilophosaurus, Dracovenator, Sinosaurus, and Crylophosaurus, recent research has supported a more narrowly defined Dilophosauridae family containing only Dilophosaurus and Dracovenator and excluding Sinosaurus and Crylophosaurus.[2] This change was supported by similarities between Dracovenator, Dilophosaurus wetherilli and Zupaysaurus rougieri, suggesting these taxa might form their own clade sister to Dilophosauridae, although there is no definitive evidence.[10] Sinosaurus and Crylophosaurus are also now classified as basal tetanurans.[11] While all of the dinosaur genera once within Dilophosauridae are characterized by a distinctive cranial crest, it is thought that this distinctive trait was convergently evolved in dilophosaurids and basal tetanurans, and thus not all are necessarily derived from the same common ancestor.

The following family tree illustrates a synthesis of the relationships of the early theropod groups compiled by Hendrickx et al. in 2015, and follows more recent research showing a more restricted Dilophosauridae.[2]

Neotheropoda

Coelophysidae Coelophysis size flipped

Liliensternus

Zupaysaurus

Dilophosauridae

Dilophosaurus Dilophosaurus wetherilli (flipped)

Dracovenator

Averostra

Ceratosauria Ceratosaurus nasicornis DB

Tetanurae

Cryolophosaurus Cryolophosaurus reconstruction (flipped)

Sinosaurus

Monolophosaurus

Orionides Austroraptor Restoration (flipped)

Paleobiology

All dilophosaurids are known for large, distinctive, head crests. These crests have been thought to have had many different uses, including being used for display, to attract mates, or intimidate rivals. It has been suggested that the crests symbolized sexual dimorphism, but this interpretation of the crests is controversial. Another distinctive cranial feature is a notch between the premaxilla and maxilla, giving dilophosaurids a crocodile-like appearance. This makes some people, for example David B. Norman, suspect that their front teeth were too weak to bring down prey, and that they were scavengers. Tracks found in Utah might show that dilophosaurids could swim, implying that they fed on fish.[11]

Palaeoecology

While dilophosaurids flourished during the Early Jurassic, they were mostly extinct by the end of the Early Jurassic period (201.3-174.1 Ma). Dilophosaurid fossils have been found on two continents: Dilophosaurus wetherilli was discovered in North America and Dracovenator regenti[10] was discovered in South Africa. The taxa previously considered Dilophosaurids, Sinosaurus and Cryolophosaurus, have been found in China (Dong 2003; Xing et al. 2013a, 2014) and Antarctica,[7] respectively.

A lack of endemism within the Dilophosauridae family makes it difficult to pinpoint a single geographic origin for the group.[7] Dilophosaurus fossils originate from the Kayenta Formation (dates to Early Jurassic, 196–183 million years ago) of the southwest region of the United States. In addition to Dilophosaurus, ‘Syntarsus’ kayentakatae is another taxa from the Kayenta Formation, despite being distantly related to Dilophosaurus.[7] Syntarsus similarly occurred in the Upper Elliot Formation of South Africa, where both Dracovenator and Coelophysis rhodesiensis have been found in a similar region despite not being closely related to one another.[7]

During the Early Jurassic, many unrelated basal theropods existed in similar geographic regions, as exemplified through the Kayenta Formation and the Upper Elliot Formation.[7] A hypothesis proposed by Smith et al. (2007) was that there may have been resource partitioning within different geographic regions of the Early Jurassic based on differences in body size. This hypothesis, with more evidence, would help explain the lack of endemism observed in the fossil record of the Early Jurassic basal theropods.

References

  1. ^ Holtz, Thomas R. Jr. (2012) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2011 Appendix.
  2. ^ a b c 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.
  3. ^ L., Atkinson. "What is Dilophosauridae?".
  4. ^ a b Holtz, Tom. "Dilophosaurs". Palaeos. Retrieved 22 November 2013.
  5. ^ Holtz, Thomas R. Jr. (2012) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2011 Appendix.
  6. ^ Wang, G. F., You, H. L., Pan, S. G., & Wang, T. (2017). A new crested theropod dinosaur from the Early Jurassic of Yunnan Province, China. Vertebrata PalAsiatica, 55(2), 177-186.
  7. ^ a b c d e f Smith, N.D., Makovicky, P.J., Pol, D., Hammer, W.R., and Currie, P.J. (2007). "The Dinosaurs of the Early Jurassic Hanson Formation of the Central Transantarctic Mountains: Phylogenetic Review and Synthesis". U.S. Geological Survey and The National Academies doi:10.3133/of2007-1047.srp003
  8. ^ Charig, A.J. and Milner, A.C. (1990). "The systematic position of Baryonyx walkeri, in the light of Gauthier's reclassification of the Theropoda." In Carpenter, K. and Currie, P.J. (eds.), Dinosaur Systematics: Perspectives and Approaches, Cambridge University Press: 127-140.
  9. ^ a b Smith, N.D., Makovicky, P.J., Pol, D., Hammer, W.R., and Currie, P.J. (2007). "The dinosaurs of the Early Jurassic Hanson Formation of the Central Transantarctic Mountains: Phylogenetic review and synthesis." In Cooper, A.K. and Raymond, C.R. et al. (eds.), Antarctica: A Keystone in a Changing World––Online Proceedings of the 10th ISAES, USGS Open-File Report 2007-1047, Short Research Paper 003, 5 p.; doi:10.3133/of2007-1047.srp003.
  10. ^ a b Yates, A. M. (2005) A new theropod dinosaur from the Early Jurassic of South Africa and its implications for the early evolution of theropods.
  11. ^ a b Xing, L.D. (2012). "Sinosaurus from Southwestern China". Department of Biological Sciences, University of Alberta. Edmonton: 1–286.
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.

Ceratosauria

Ceratosaurs are members of a group of theropod dinosaurs defined as all theropods sharing a more recent common ancestry with Ceratosaurus than with birds. Ceratosaurs are believed to have diverged from the rest of Theropoda by the early Jurassic, however, the oldest confirmed discovered specimens date to the Late Jurassic. According to the majority of the latest research, Ceratosauria includes the Late Jurassic to Late Cretaceous theropods Ceratosaurus, Elaphrosaurus, and Abelisaurus, found primarily (though not exclusively) in the Southern Hemisphere. Originally, Ceratosauria included the above dinosaurs plus the Late Triassic to Early Jurassic Coelophysoidea and Dilophosauridae, implying a much earlier divergence of ceratosaurs from other theropods. However, most recent studies have shown that coelophysoids and dilophosaurids do not form a natural group with other ceratosaurs, and are excluded from this group.Ceratosauria derives its names from the type species, Ceratosaurus nasicornis, described by O.C. Marsh in 1884. A moderately large predator from the Late Jurassic, Ceratosaurus nasicornis, was the first ceratosaur to be discovered. Ceratosaurs are generally moderately large in size, with some exceptions like the larger Carnotaurus and the significantly smaller noasaurs. The major defining characteristics of Ceratosauria include a robust skull with increased ornamentation or height and a shortening of the arms. Both of these characteristics are generally accentuated in later members of the group, such as the abelisaurs, whereas more basal species such as C. nasicornis appear more similar to other basal theropods. The highly fragmented nature of the ceratosaur fossil record, means that the characteristics, relationships, and early history of Ceratosauria remain mysterious and highly debated.

Coelophysidae

Coelophysidae is a family of primitive carnivorous theropod dinosaurs. Most species were relatively small in size. The family flourished in the Late Triassic and Early Jurassic periods, and has been found on numerous continents. Many members of Coelophysidae are characterized by long, slender skulls and light skeletons built for speed. One member, Coelophysis, displays the earliest known furcula in a dinosaur.Under cladistic analysis, Coelophysidae was first defined by Paul Sereno in 1998 as the most recent common ancestor of Coelophysis bauri and Procompsognathus triassicus, and all of that common ancestor's descendants. However, Tykoski (2005) has advocated for the definition to change to include the additional taxa of "Syntarsus" kayentakatae and Segisaurus halli. Coelophysidae is part of the superfamily Coelophysoidea, which in turn is a subset of the larger Neotheropoda clade. As part of Coelophysoidea, Coelophysidae is often placed as sister to the Dilophosauridae family, however, the monophyly of this clade has often been disputed. The older term "Podokesauridae", named 14 years prior to Coelophysidae (which would normally grant it priority), is now usually ignored, since its type specimen was destroyed in a fire and can no longer be compared to new finds.

Cryolophosaurus

Cryolophosaurus ( or ; "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.

Dilophosaurus

Dilophosaurus ( dy-LOHF-o-SOR-əs) is a genus of theropod dinosaur that lived in what is now North America during the Early Jurassic, about 193 million years ago. Three skeletons were discovered in northern Arizona in 1940, and the two best preserved were collected in 1942. The most complete specimen became the holotype of a new species in the genus Megalosaurus, named M. wetherilli by Samuel P. Welles in 1954. Welles found a larger skeleton belonging to the same species in 1964. Realizing it bore crests on its skull, he assigned the species to the new genus Dilophosaurus in 1970, as Dilophosaurus wetherilli. The genus name means "two-crested lizard", and the species name honors John Wetherill, a Navajo councilor. Further specimens have since been found, including an infant. Footprints have also been attributed to the animal, including resting traces. Another species, Dilophosaurus sinensis from China, was named in 1993, but was later found to belong to the genus Sinosaurus.

At about 7 meters (23 ft) in length, with a weight of about 400 kilograms (880 lb), Dilophosaurus was one of the earliest large predatory dinosaurs, though it was smaller than some later theropods. It was slender and lightly built, and the skull was proportionally large, but delicate. The snout was narrow, and the upper jaw had a gap or kink below the nostril. It had a pair of longitudinal, plate-shaped crests on its skull, similar to a cassowary with two crests. The mandible was slender and delicate at the front, but deep at the back. The teeth were long, curved, thin, and compressed sideways. Those in the lower jaw were much smaller than those of the upper jaw. Most of the teeth had serrations at their front and back edges. The neck was long, and its vertebrae were hollow, and very light. The arms were powerful, with a long and slender upper arm bone. The hands had four fingers: the first was short but strong and bore a large claw, the two following fingers were longer and slenderer with smaller claws, and the fourth was vestigial. The thigh bone was massive, the feet were stout, and the toes bore large claws.

Dilophosaurus is a member of the family Dilophosauridae along with Dracovenator, a group placed between the Coelophysidae and later theropods. Dilophosaurus would have been active and bipedal, and may have hunted large animals; it could also have fed on smaller animals and fish. Due to the limited range of movement and shortness of the forelimbs, the mouth may instead have made first contact with prey. The function of the crests is unknown; they were too weak for battle, but may have been used in visual display, such as species recognition and sexual selection. It may have grown rapidly, attaining a growth rate of 30 to 35 kilograms (66 to 77 lb) per year early in life. The holotype specimen had multiple paleopathologies, including healed injuries and signs of a developmental anomaly. Dilophosaurus is known from the Kayenta Formation, and lived alongside dinosaurs such as Megapnosaurus and Sarahsaurus. Dilophosaurus was featured in the novel Jurassic Park and its movie adaptation, wherein it was given the fictional abilities to spit venom and expand a cowl on its neck, as well as being smaller than the real animal. It was designated as the state dinosaur of Connecticut in 2017.

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.

Dracovenator

Dracovenator () is a genus of dilophosaurid theropod dinosaur that lived approximately 201 to 199 million years ago during the early part of the Jurassic Period in what is now South Africa. Dracovenator was a medium-sized, moderately-built, ground-dwelling, bipedal carnivore, that could grow up to an estimated 7 m (23.0 ft) long. Its type specimen was based on only a partial skull that was recovered.

Haya griva

Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.

Jingshanosaurus

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

Liliensternus

Liliensternus is an extinct genus of basal Neotheropod dinosaur that lived approximately 210 million years ago during the latter part of the Triassic Period in what is now Germany. Liliensternus was a moderate-sized, bipedal, ground-dwelling carnivore, that could grow up to 5.15 m (16.9 ft) long. It is the best represented Triassic theropod from Europe and one of the largest known.

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.

Notatesseraeraptor

Notatesseraeraptor ("feature mosaic tile thief"; from the Latin "nota", feature; "tesserae", tiles used to make a mosaic, in reference to the mixture of features normally found on dilophosaurids and coelophysoids; and "raptor", thief) is a genus of carnivorous theropod dinosaur that lived during the Late Triassic of what is now Switzerland. It was an early member of Neotheropoda with affinities to Dilophosaurus and Averostra. The new genus and species Notatesseraeraptor frickensis was named by Marion Zahner and colleagues in 2019.Since 1961, at the clay pit of Gruhalde, exploited by Tonwerke Keller, numerous fossils of Plateosaurus have been found. At a somewhat higher layer, in the spring of 2006, amateur paleontologist Michael Fisher discovered the postcranial skeleton of a small theropod. In 2009, the skull was secured. The fossils were unearthed and prepared by Ben Pabst and team. Initially the skeleton was provisionally referred to Coelophysidae. In 2008, parts of the postcranial skeleton were described in a master's thesis by Jasmina Christine Hugi. Lui Unterassner described the shoulder girdle and stomach content in his thesis of 2009, while Marion Zahner dedicated a thesis to the skull in 2014.In 2019, the type species Notatesseraeraptor frickensis gen. et sp. nov. was named and described by Marion Zahner and Winand Brinkmann. The generic name combines the Latin nota, "trait", tesserae, "mosaic tiles", and raptor, "predator". It refers to it being a carnivorous species showing a mix of traits of the Dilophosauridae and Coelophysoidea. The specific name refers to a provenance from the municipality of Frick in the Aargau. It represents the first Mesozoic theropod named from Switzerland.

Orionides

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

Orodrominae

Orodrominae is a subfamily of parksosaurid dinosaurs from the Cretaceous of North America and Asia.

Theropoda

Theropoda ( or , from Greek θηρίον "wild beast" and πούς, ποδός "foot") or theropods () are a dinosaur suborder that is characterized by hollow bones and three-toed limbs. They are generally classed as a group of saurischian dinosaurs, although a 2017 paper has instead placed them in the proposed clade Ornithoscelida as the closest relatives of the Ornithischia. Theropods were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores, omnivores, piscivores, and insectivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago (Ma) and included the sole large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 10,500 living species.

Xixiposaurus

Xixiposaurus is a genus of prosauropod dinosaur which existed in what is now Lower Lufeng Formation, China during the lower Jurassic period. It was first named by Sekiya Toru in 2010 and the type species is Xixiposaurus suni.

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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