Ornithodesmus

Ornithodesmus (meaning "bird link") is a genus of small, dromaeosaurid dinosaur from the Isle of Wight in England, dating to about 125 million years ago. The name was originally assigned to a bird-like sacrum (a series of vertebrae fused to the hip bones), initially believed to come from a bird[1] and subsequently identified as a pterosaur. More complete pterosaur remains were later assigned to Ornithodesmus, until recently a detailed analysis determined that the original specimen in fact came from a small theropod, specifically a dromaeosaur. All pterosaurian material previously assigned to this genus has been renamed Istiodactylus.

Ornithodesmus
Temporal range: Early Cretaceous, 125 Ma
Ornithodesmus cluniculus
Illustration of the sacrum in multiple views
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Dromaeosauridae
Genus: Ornithodesmus
Seeley, 1887
Species:
O. cluniculus
Binomial name
Ornithodesmus cluniculus
Seeley, 1887

Description

As it is only known from isolated vertebrae, little is known about the appearance of Ornithodesmus. The neural spines of the vertebrae are fused and form a blade over the 9.6 centimetres long sacrum, which is slightly arched. The bases of the neural spines form a lateral platform, and the first two vertebrae of the sequence have deep hollow cavities, which formed space for air sacs.[2]

Based on its apparent identity as a dromaeosaur, it was probably carnivorous, and likely measured about 1.8 meters (5.9 feet) long in life. Dromaeosaur teeth probably belonging to a velociraptorine are known from the same formation, but are too large to have belonged to Ornithodesmus; rather, these must have come from a theropod closer in size to the giant Utahraptor.[3]

History and classification

Ornithodesmus cluniculus was first described by Harry Govier Seeley in 1887, based on a set of six fused vertebrae from the hip (sacrum), specimen number BMNH R187, found by William D. Fox in the Wessex Formation of Brook Bay. Seeley thought the bones came from a primitive bird, and gave it a name meaning "bird link",[1] from Greek ὄρνις (ornis), "bird", en δεσμός (desmos), "link". The specific name cluniculus means "little buttock" in Latin, a reference to the small thighs indicated by the size of the specimen.

Later that year, John Hulke (in an anonymous paper) suggested the remains actually belonged to a pterosaur.[4] Seeley himself later changed his opinion when he described the complete skeleton (specimen number BMNH R176) of a new pterosaur species he believed was closely related to O. cluniculus. He named this new species Ornithodesmus latidens in 1901. Although he now considered it a pterosaur, Seeley at the time still considered Ornithodesmus close to the origin of birds, and suggested the (now defunct) theory that birds and pterosaurs shared a close common ancestry.[5] For over a century following this, the pterosaur O. latidens was used as the standard example of Ornithodesmus, and the fragmentary type specimen was largely ignored. In 1913, Reginald Walter Hooley named a new family to distinguish Ornithodesmus from other large pterosaurs known at the time, Ornithodesmidae.[6]

In 1993, Stafford C. Howse and Andrew Milner re-examined the type specimen of O. cluniculus and determined that Seeley had incorrectly referred the pterosaur species to this genus. They identified O. cluniculus as a theropod dinosaur. Specifically, they suggested it was a troodontid, based on its similarity to the supposed troodontid specimen BMNH R4463.[7] However, later study by Peter Makovicky and Mark Norell showed this specimen to be a dromaeosaurid; because of this mis-identification, they suggested Ornithodesmus was likely a dromaeosaurid as well.[8] Darren Naish and colleagues in 2001 argued against a dromaeosaurid identity for Ornithodesmus, suggesting instead it was related to the ceratosaurs or coelophysids.[2] However, those scientists later changed their opinions, publishing a paper in 2007 that agreed with previous studies and classifying Ornithodesmus as a dromaeosaurid.[3]

The more complete pterosaur specimens that had long been associated with the name Ornithodesmus were given a new name in 2001, Istiodactylus.[9]

See also

References

  1. ^ a b Seeley, H. (1887). "On a sacrum, apparently indicating a new type of Bird, Ornithodesmus cluniculus, Seeley, from the Wealden of Brook." Quarterly Journal of the Geological Society of London, 42: 206-211.
  2. ^ a b Naish, D. Hutt, and Martill, D.M. (2001). "Saurischian dinosaurs: theropods." in Martill, D.M. and Naish, D. (eds). Dinosaurs of the Isle of Wight. The Palaeontological Association, Field Guides to Fossils. 10, 242-309.
  3. ^ a b Naish, D. and Martill, D. M. (2007). "Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia." Journal of the Geological Society, London, 164(3): 493-510
  4. ^ Anonymous (1887). "Discussion (on Ornithodesmus and Patricosaurus)." Quarterly Journal of the Geological Society of London, 43: 219-220.
  5. ^ Seeley, H. (1901). Dragons of the Air. London: Methuen & Co. 239 pp.
  6. ^ Hooley, R.W. (1913). "The skeleton of Ornithodesmus latidens; an Ornithosaur from the Wealden Shales of Atherfield (Isle of Wight)." Quarterly Journal of the Geological Society, 69(1-4): 372-422.
  7. ^ Howse, S.C.B. and Milner, A.R. (1993). "Ornithodesmus—a maniraptoran theropod dinosaur from the Lower Cretaceous of the Isle of Wight, England." Palaeontology, 36: 425–437.
  8. ^ Norell, M.A. and Makovicky, P. (1997). "Important features of the dromaeosaur skeleton: Information from a new specimen." American Museum Novitates, 3215: 1-28.
  9. ^ Howse, Milner and Martill (2001). "Pterosaurs." in Martill, D.M. and Naish, D. (eds.). Dinosaurs of the Isle of Wight. The Palaeontological Association, London. pp. 324-335.

External links

1887 in paleontology

Paleontology or palaeontology (from Greek: paleo, "ancient"; ontos, "being"; and logos, "knowledge") is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1887.

Dromaeosaurinae

Dromaeosaurinae is a subfamily of Dromaeosauridae. Most dromaeosaurines lived in what is now the United States and Canada, as well as Mongolia, and possibly Denmark as well. Isolated teeth that may belong to African dromaeosaurines have also been discovered in Ethiopia. These teeth date to the Tithonian stage, of the Late Jurassic Period.All North American and Asian dromaeosaurine dinosaurs from the Late Cretaceous were generally small, no more than 1.8 metres (5.9 ft) long, in Dromaeosaurus and Adasaurus. However, among the dromaeosaurines were the largest dromaeosaurs ever; Dakotaraptor was ~5.5 metres (18 ft) long, Achillobator 6 metres (20 ft), and Utahraptor up to ~7 metres (23 ft).

Graciliraptor

Graciliraptor (meaning "graceful thief") is a genus of theropod dinosaur from the early Cretaceous Period. It is a microraptorine dromaeosaurid.

The type species Graciliraptor lujiatunensis was first named and described in 2004 by Xu Xing and Wang Xiaoling. The generic name is derived from Latin gracilis and raptor. The specific name refers to the village Lujiatun where the fossil site is located. Its fossil, holotype IVPP V 13474, was found in Beipiao, Liaoning Province, China.

Halszkaraptorinae

Halszkaraptorinae is a basal ("primitive") subfamily of Dromaeosauridae that includes the enigmatic genera Halszkaraptor, Mahakala, and Hulsanpes. A comparison of the fossils of Halszkaraptor with the bones of extant crocodilians and aquatic birds revealed evidence of a semiaquatic lifestyle. The group is named after Polish paleontologist Halszka Osmólska.

Hulsanpes

Hulsanpes is a genus of dromaeosaurid theropod dinosaur from Mongolia that lived during the Late Cretaceous.

Istiodactylidae

Istiodactylidae is a small family of pterosaurs. This family was named in 2001 after the type genus Istiodactylus was discovered not to be a member of the genus Ornithodesmus.

Remains of taxa that can be confidently assigned to Istiodactylidae have been found in the UK and China, in rocks dating from the Early Cretaceous period (Barremian to Aptian stage). Arbour and Currie (2011) described Canadian Gwawinapterus beardi as a member of Istiodactylidae living in the late Cretaceous (upper Campanian stage); however, Witton (2012) suggested the tooth replacement pattern in this animal does not match that of pterosaurs, suggesting that the species might be non-pterosaurian. Additional research suggested that the species was in fact a fish. The earliest known species might be Archaeoistiodactylus linglongtaensis, from the Middle Jurassic of China; however, it also has been suggested that the holotype specimen of this species might actually be a poorly preserved specimen of Darwinopterus. Hongshanopterus, a supposed istiodactylid from China, has been reclassified as a non-istiodactylid member of Ornithocheiroidea of uncertain phylogenetic placement by Witton (2012).Istiodactylids were medium sized pterosaurs with flat, rounded jaws similar to that of a duck. They had small teeth lining their jaws, however.

Istiodactylus

Istiodactylus is a genus of pterosaur that lived during the Early Cretaceous period, about 120 million years ago. The first fossil was discovered on the English Isle of Wight in 1887, and in 1901 became the holotype specimen of a new species, O. latidens (Latin for "wide tooth"), in the genus Ornithodesmus. This species was moved to its own genus, Istiodactylus, in 2001; this name is Greek for "sail finger". More specimens were described in 1913, and Istiodactylus was the only pterosaur known from three-dimensionally preserved fossils for much of the 20th century. In 2006, a species from China, I. sinensis, was assigned to Istiodactylus, but it has since been found to belong to a different genus.

Istiodactylus was a large pterosaur; estimates of its wingspan range from 4.3 to 5 metres (14 to 16 ft). Its skull was about 45 centimetres (18 in) long, and was relatively short and broad for a pterosaur. The front of the snout was low and blunt, and bore a semicircle of 48 teeth. The triangular teeth were closely spaced, interlocked, and formed a "razor-edged" outline. The lower jaw also had a tooth-like projection that occluded with the teeth. The skull had a very large naso-antorbital opening (which combined the antorbital fenestra and the opening for the bony nostril) and a slender eye socket. Some of the vertebrae were fused into a notarium, to which the shoulder blades connected. It had very large forelimbs, with a wing-membrane distended by a long wing-finger, but the hindlimbs were very short.

Until the 21st century, Istiodactylus was the only known pterosaur of its kind, and was placed in its own family, Istiodactylidae, within the group Ornithocheiroidea. Istiodactylus differed from other istiodactylids in having a proportionally shorter skull. The distinctive teeth of Istiodactylus indicate that it was a scavenger that may have used its teeth to sever morsels from large carcasses in the manner of a cookie cutter. The wings of Istiodactylus may have been adapted for soaring, which would have helped it find carcasses before terrestrial carnivores. Istiodactylus is known from the Wessex Formation and the younger Vectis Formation, which represent river and coastal environments that were shared with various pterosaurs, dinosaurs, and other animals.

Itemirus

Itemirus is a genus of theropod dinosaur from the Turonian age of the Late Cretaceous period of Uzbekistan.

Linheraptor

Linheraptor is a genus of dromaeosaurid dinosaur which lived in what is now China in the Late Cretaceous. It was named by Xu Xing and colleagues in 2010, and contains the species Linheraptor exquisitus. This bird-like dinosaur was less than 2 m (6.5 ft) long and was found in Inner Mongolia. It is known from a single, nearly complete skeleton.

Lonchodraco

Lonchodraco is a genus of pterodactyloid pterosaur from the Cretaceous of England. The genus includes species that were previously assigned to other genera.

Luanchuanraptor

Luanchuanraptor (meaning "Luanchuan thief") is a genus of dromaeosaurid theropod dinosaur from the Late Cretaceous of China. It is based on a partial skeleton from the Qiupa Formation in Luanchuan, Henan. A medium-sized dromaeosaurid, it is the first Asian dromaeosaurid described from outside the Gobi Desert or northeastern China. The fossil material is cataloged as 4HIII-0100 in the Henan Geological Museum and includes four teeth, one frontal, a neck vertebra, one or two back vertebrae, seventeen tail vertebrae, ribs, chevrons, a humerus (upper arm bone), claw and finger bones, partial shoulder and pelvic girdles, and other fragmentary bones from a moderately sized dromaeosaurid. The type species is L. henanensis, described by Lü et al. in 2007.

Prehistoric reptile

The term prehistoric reptile covers a broad category that is intended to help distinguish the dinosaurs from other prehistoric reptiles. As the dinosaurs, because of their long and successful reign for many millions of years, are almost exclusively dealt with in their own category of prehistoric life.

The category covers all the non-dinosaurian reptiles which are often erroneously considered to be dinosaurs, such as the seafaring varieties of plesiosaurs and the flying pterosaurs. Also included are ancient crocodiles such as Deinosuchus.

For information on the synapsids, which were previously known as "mammal-like reptiles" (including the well-known Dimetrodon), which are not part of the clade Sauropsida (with which "Reptilia" is generally synonymized), see Synapsid (amniotes related to mammals). For information on the ancestors of reptiles, traditionally classified as labyrinthodont amphibians, see Reptiliomorpha (reptile-like tetrapods).

Pyroraptor

Pyroraptor (meaning "fire thief") is a genus of dromaeosaurid dinosaur from the Late Cretaceous of what is now southern France, it lived during the late Campanian and early Maastrichtian stages, approximately 70.6 million years ago. It is known from a single partial specimen that was found in Provence in 1992. The animal was named Pyroraptor olympius by Allain and Taquet in 2000.

Reginald Hooley

Reginald Walter Hooley (5 September 1865 – 5 May 1923) was a businessman and amateur paleontologist, collecting on the Isle of Wight.

Saurornitholestinae

Saurornitholestinae is a subfamily of dromaeosaurid dinosaurs. The saurornitholestines currently include three monotypic genera: Atrociraptor marshalli, Bambiraptor feinbergorum, and Saurornitholestes langstoni. All are medium-sized dromaeosaurs from the Late Cretaceous of western North America. The group was originally recognized by Longrich and Currie as the sister taxon to a clade formed by the Dromaeosaurinae and Velociraptorinae. However, not all phylogenetic analyses recover this group.

Unenlagiinae

Unenlagiinae is a subfamily of dromaeosaurid theropods. Unenlagiines are known from South America and Antarctica.

Unquillosaurus

Unquillosaurus (meaning "Unquillo river lizard") is a genus of maniraptoran dinosaur from the Late Cretaceous Period, discovered in Argentina. Known only from a single fossilized pubis (a pelvic bone), its total body length may have reached 2 to 3 metres (6.6 to 9.8 ft).

Variraptor

Variraptor ( VARR-i-rap-tor; "Var thief") is a genus of coelurosaurian theropod dinosaur from the Late Cretaceous of France.

Yurgovuchia

Yurgovuchia is an extinct genus of dromaeosaurid theropod dinosaur known from the Early Cretaceous (probably Barremian stage) of Utah. It contains a single species, Yurgovuchia doellingi. According to a phylogenetic analysis performed by its describers, it represents an advanced dromaeosaurine, closely related to Achillobator, Dromaeosaurus and Utahraptor.

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