Daemonosaurus

Daemonosaurus (pron.:"DAY-mow-no-SORE-us") is an extinct genus of theropod dinosaur from the Late Triassic of New Mexico. Fossils have been found from deposits in the Chinle Formation, which is latest Triassic in age. While theropods had diversified into several specialized groups by this time, Daemonosaurus is a basal theropod that lies outside the clade Neotheropoda. Daemonosaurus is unusual among early theropods in that it had a short skull and long protruding teeth.[1][2]

Daemonosaurus
Temporal range: Rhaetian
~205.6–201.6 Ma
Daemonosaurus chauliodus skull
Reconstructed skull, which interprets the "buck teeth" as being due to the teeth loosening from their sockets
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Genus: Daemonosaurus
Sues et al. 2011
Species:
D. chauliodus
Binomial name
Daemonosaurus chauliodus
Sues et al. 2011

Description

Daemonosaurus chauliodus
Recreation

Based on the proportions of related theropods, Daemonosaurus is estimated to have been around 1.5 m (5 feet) long.[2] Other estimates suggest that Daemonosaurus was at most 2.2 m (7 ft) long and weighed 22 kilograms (49 pounds).[3] The skull of Daemonosaurus differs considerably from all other Triassic theropods. The snout is short and bears large premaxillary and maxillary teeth in the upper jaw. Procumbent teeth project forward from the tips of the upper and lower jaws,[1] which is highlighted in the species name chauliodis that roughly means "buck-toothed".[4] Daemonosaurus is unique among Triassic theropods because it has an unusually short snout, and all other early theropods had long heads and jaws. Like the coelophysoids, Daemonosaurus has a kink in its upper jaws, between the maxilla and the premaxilla.

The proportionately large orbit, the short snout, and the apparent lack of fusion between the bones of the braincase suggest that the holotype specimen CM 76821 may be an example of a juvenile dinosaur. On the other hand, the closure (fusion) of the neurocentral sutures in the vertebrae suggest a mature individual.

Discovery

Daemonosaurus is known from the single holotype CM 76821, which consists of a skull, mandibles, an atlas bone, an axis bone, neck vertebrae, and rib fragments discovered at Ghost Ranch. Ghost Ranch is famous for an abundance of fossils of the similar theropod Coelophysis. Fossils of Coelophysis were present on the same block that contained the skull of Daemonosaurus, which was uncovered by a volunteer at the State Museum of Pennsylvania.[1][2] In 2011, Fred Bervoets noted that "it is possible that additional postcranial bones will be retrieved during further preparation of the large block C-4-81 in which CM 76821 was discovered in association with skeletal remains of C. bauri."

Daemonosaurus was named by Hans-Dieter Sues, Sterling J. Nesbitt, David S. Berman and Amy C. Henrici in the journal Proceedings of the Royal Society B in 2011 and the type species is Daemonosaurus chauliodus. The generic name Daemonosaurus is derived from the Greek words "daimon" (δαίμων) meaning "demon" and "sauros" (σαύρα) meaning "reptile". The specific name is derived from the Greek word "chauliodous" (χαυλιόδους) meaning "prominent toothed", which is in reference to its procumbent front teeth.[1]

Classification

Daemonosaurus is a basal theropod that lies outside the clade Neotheropoda,[5] a group that includes more advanced Triassic theropods like Coelophysis and their descendants. With such a basal position, it represents a lineage that extended from the earliest radiation of dinosaurs in the Middle Triassic with forms such as Eoraptor and Herrerasaurus from South America. A phylogenetic analysis conducted in its original description found Daemonosaurus chauliodus to be closely related to Tawa hallae, a theropod that was described from Ghost Ranch in 2009, and the Neotheropoda. Although the two theropods are closely related, Tawa was found in a quarry that is slightly older than Ghost Ranch. Sues et al. (2011) noted that the discovery of Daemonosaurus provided "additional support for the theropod affinities of both Eoraptor and Herrerasauridae and (demonstrated) that lineages from the initial radiation of Dinosauria persisted until the end of the Triassic."[5] Below is a cladogram based on the phylogenetic analysis conducted by Sues et al. in 2011, showing the relationships of Daemonosaurus:[1]

Theropoda 

Staurikosaurus

Herrerasaurus

Chindesaurus

Eoraptor

Daemonosaurus

Tawa

 Neotheropoda 

Megapnosaurus

Coelophysis

Liliensternus

Zupaysaurus

Cryolophosaurus

Dilophosaurus

Jurassic theropods

Examination of this genus by Sues et al. (2011) demonstrates that Daemonosaurus is separate and distinct from its other contemporaries.[1] Daemonosaurus differs from Herrerasaurus based on key features in the skull and because it has much larger teeth in the premaxilla. Daemonosaurus differs from Eodromaeus based on features of the jaw bone, skull, cheek bones, and because it has much larger teeth in the premaxilla. Daemonosaurus differs from Eoraptor lunensis based on the presence of much larger premaxillary and anterior maxillary teeth and a much more restricted antorbital fossa on the maxilla. Daemonosaurus differs from Tawa hallae and Coelophysis bauri in features of the skull bones. Daemonosaurus differs from Chindesaurus bryansmalli in features of the cervical vertebrae.

Distinguishing anatomical features

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group.

According to Sues et al. (2011), Daemonosaurus can be distinguished based on the following features:[5]

  • the skull is proportionately deep and narrow, with a short antorbital region
  • the antorbital fenestra is nearly the same size as the external naris (possible autapomorphy)
  • the long posterior process of the premaxilla almost contacts the anterior process of the lacrimal bone (possible autapomorphy)
  • the ventral process of the lacrimal bone has a slender posterior projection extending along anterodorsal margin of the jugal bone
  • the jugal is dorsoventrally deep and has a prominent lateral ridge; and the alveolar margin of the dentary is downturned at the symphysis
  • the postorbital with anterolateral overhang over the orbit; and the prefrontal is large and occupies about 50% of the dorsal margin of the orbit
  • the first two dentary teeth are large and procumbent; and the premaxillary and anterior maxillary teeth are much enlarged relative to the posterior maxillary teeth
  • the third cervical vertebra has a deep, rimmed, ovoid pleurocoels on the anterolateral surfaces of both the centrum and the neural arch

Paleoecology

Provenance and occurrence

The only specimen of Daemonosaurus was recovered at the Ghost Ranch (Whitaker) quarry at the Siltstone Member of the Chinle Formation in Rio Arriba County, New Mexico. Its remains were collected in the 1980s by E.H. Colbert in pebbly, calcareous conglomerate from the Rhaetian stage of the Triassic period, approximately 208 to 201 million years ago. This specimen is housed in the collection of the Carnegie Museum of Natural History, in Pittsburgh, Pennsylvania.

Fauna and habitat

Ghost Ranch was located close to the equator 200 million years ago, and had a warm, monsoon-like climate with heavy seasonal precipitation. Whitaker Quarry, at Ghost Ranch, New Mexico, was the paleoenvironment for a diverse collection of rhynchocephalians, like Whitakersaurus, archosauromorphs and archosaurs, parasuchid reptiles like Redondasaurus, crocodilians like Hesperosuchus, pseudosuchians like Effigia, the dinosauromorph Eucoelophysis, and the dinosaur Coelophysis.[6]

Taphonomy

The multitude of specimens deposited so closely together at Ghost Ranch was probably the result of a flash flood event. Such flooding was commonplace during this period of the Earth's history and, indeed, the nearby Petrified Forest of Arizona is the result of a preserved log jam of tree trunks that were caught in one such flood. In 1989, Colbert noted that the Daemonosaurus specimen and several Coelophysis specimens were washed into a small pond, where they drowned and were buried by a sheet flood event from a nearby river."[6]

References

  1. ^ a b c d e f Hans-Dieter Sues; Sterling J. Nesbitt; David S. Berman & Amy C. Henrici (2011). "A late-surviving basal theropod dinosaur from the latest Triassic of North America". Proceedings of the Royal Society B. 278 (1723): 3459–3464. doi:10.1098/rspb.2011.0410. PMC 3177637. PMID 21490016.
  2. ^ a b c Choi, C.Q. (12 April 2011). "T. Rex had a toothy ancestor that couldn't cut it". Live Science. Retrieved 12 April 2011.
  3. ^ "Daemonosaurus". DinoChecker.com. Retrieved 5 May 2013.
  4. ^ "Missing link ties older to newer dinosaurs". CBS News. Retrieved 2011-04-14.
  5. ^ a b c H.D. Sues, S. J. Nesbitt, D. S. Berman and A. C. Henrici. 2011. A late-surviving basal theropod dinosaur from the latest Triassic of North America. Proceedings of the Royal Society B 278:3459-3464
  6. ^ a b E. H. Colbert. 1989. The Triassic dinosaur Coelophysis. Museum of Northern Arizona Bulletin 57:1-174
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.

Chindesaurus

Chindesaurus ( CHIN-di-SAWR-əs) is a genus of herrerasaurid dinosaur that lived approximately 235-210 million years ago during the latter part of the Triassic Period in what is now the Southwestern United States. Chindesaurus was a small, bipedal carnivore that could grow up to 2 to 2.3 m (6.6 to 7.5 ft) long.

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.

Eoraptor

Eoraptor () was one of the earliest-known dinosaurs, living approximately 231 to 228 million years ago, during the Late Triassic in Western Gondwana, in the region that is now northwestern Argentina. It was a small, lightly-built, basal theropod dinosaur. It is known from several well-preserved skeletons. When first described in 1993, it was considered to be one of the earliest, if not the earliest-known dinosaur. Eoraptor has heterodont dentition, suggesting that it was omnivorous, and that this feeding strategy had evolved early on in dinosaurs.

Herrerasauridae

Herrerasauridae is a family of carnivorous basal saurischian dinosaurs. They are among the oldest known dinosaurs, first appearing in the fossil record around 233.23 million years ago (Late Triassic), before becoming extinct by the end of the Triassic period. Herrerasaurids were relatively small-sized dinosaurs, normally not more than 4 metres (13 ft) long. The best known representatives of this group are from South America (Brazil, Argentina), where they were first discovered in the 1960s. A nearly complete skeleton of Herrerasaurus ischigulastensis was discovered in the Ischigualasto Formation in San Juan, Argentina, in 1988. Less complete herrerasaurids have been found in North America, and they may have inhabited other continents as well.

Herrerasaurid anatomy is unusual and specialized, and they are not considered to be ancestral to any later dinosaur group. They only superficially resemble theropods and often present a mixture of very primitive and derived traits. The acetabulum is only partly open, and there are only two sacral vertebrae, the lowest number among dinosaurs. The pubic bone has a derived structure, being rotated somewhat posteriorly and folded to create a superficially tetanuran-like terminal expansion, especially prominent in H. ischigulastensis. The hand is primitive in having five metacarpals and the third finger longer than the second, but resembles those of theropods in having only three long fingers, with curved claws. Herrerasaurids also have a hinged mandible, which is also found in theropods.

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.

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.

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.

Orodrominae

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

Raeticodactylidae

Raeticodactylidae is a family of eudimorphodontoid eopterosaurian pterosaurs that lived in Switzerland during the Late Triassic. The family includes Caviramus, and the type genus Raeticodactylus, which are both known from the Kössen Formation, around 205 mya. Raeticodactylidae was first used in 2014 by Andres et al., as a group of all pterosaurs closer to Raeticodactylus than Eudimorphodon. The following phylogenetic analysis follows the topology of Andres et al. (2014).

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).

Siltstone Member

The Siltstone Member was part of the Chinle Formation in New Mexico. It dates back to the Rhaetian in the Late Triassic.

Paleobiota

Fish

Synorichthys, a small fish of redfieldiidae

Chinlea, a coelacanth

Rhynchocephalians

Whitakersaurus, a tuatara

Archosaurs

Vancleavea

Coelophysis bauri

Daemonosaurus

Eucoelophysis

Hesperosuchus

Effigia

Redondasaurus

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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