Lophostropheus

Lophostropheus (pron.:" LOAF-oh-STRO-fee-us") is an extinct genus of coelophysoid theropod dinosaur that lived approximately 200 million years ago during the boundary between the Late Triassic Period and the Early Jurassic Period, in what is now Normandy, France. Lophostropheus is one of the few dinosaurs that may have survived the Triassic–Jurassic extinction event. Lophostropheus was a small to medium-sized, moderately-built, ground-dwelling, bipedal carnivore, that could grow up to 3 m (9.8 ft) long. Over the years it had been incorrectly classified as Halticosaurus and Liliensternus, but was later recognized as a new genus and was reassigned to Lophostropheus in 2007.

Lophostropheus
Temporal range: Late Triassic/Early Jurassic, 200 Ma
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Superfamily: Coelophysoidea
Genus: Lophostropheus
Ezcurra & Cuny, 2007
Species
Synonyms

Etymology

The composite term Lophostropheus is derived from the Greek words "lophè" (λόφη) meaning "crest" and the word "stropheus" (στροφεύς) meaning "pertaining to the vertebrae";[1] thus, "crest vertebrae". This naming is a reference to the prominent dorsal and ventral laminae observed in the cranial cervical vertebrae. The specific name, "airelensis" is a reference to the locality where the specimen was discovered, the Airel Quarry. Lophostropheus was described and named by Argentine paleontologist Martin Ezcurra (Museo Argentino de Ciencias Naturales) and French paleontologist Gilles Cuny of the Université Pierre et Marie Curie in 2007, and the type species is Lophostropheus airelensis.

Description

Estimates suggest that Lophostropheus was at best 3 m (10 ft) long and weighed 100 kilograms (220 pounds) at most.[2] It is based on a partial skeleton first described in 1966 as a specimen of Halticosaurus.

Classification

Lophostropheus differs from other theropods in several ways. It has features reminiscent of more derived theropods, such as having a ball connection to the front of its neck vertebrae, a socket connection to the front of its tail vertebrae, and a vertical ridge on the ilium. These characteristics have all been interpreted as convergences, however.[3] It also has prominent crests on the tops and bottoms of its neck vertebrae (for which it was named),[3] and an extra pair of cavities in its neck vertebrae, unlike Liliensternus.[4] It was closer to the coelophysids, including the well-known Coelophysis, than to Liliensternus.[3] It has been assigned to the superfamily Coelophysoidea. An analysis of early dinosaurs by Baron, Norman and Barrett (2017) placed Lophostropheus in a position close to the derived theropods Sinosaurus and Cryolophosaurus.[5]

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 Ezcurra and Cuny (2007), Lophostropheus can be distinguished based on the following characteristics:

  • a moderately convex anterior articular surface of the anterior postaxial cervical vertebrae (also present in Ceratosauria+Tetanurae)
  • the last dorsal vertebral centrum has a large and oval lateral fossa (also observed in Herrerasaurus)
  • the last dorsal vertebra has a dorsoventrally well-extended hyposphene
  • an incipient concavity is present on the cranial articular surface of the cranial caudal vertebrae (also present in Ceratosauria+Tetanurae)
  • the constant length of the caudal vertebrae along the length of the tail (also in Dilophosaurus)

History of discovery

In 1966, the French paleontologists Claude Larsonneur and Albert-Félix de Lapparent described a partial theropod skeleton from the Triassic-Jurassic boundary of Normandy, found in 1959 by Claude Pareyn, as Halticosaurus sp.[6] This specimen consisted of a tooth, five neck vertebrae, two vertebrae from the back, four sacral vertebrae, tail vertebrae, portions of all the pelvic bones, and an unidentified fragment.[3] It was reinterpreted in 1993 by Gilles Cuny and Peter Galton as belonging to a new species, assigned to Liliensternus and named L. airelensis.[7] Other researchers began to notice differences between L. airelensis and the type species, L. liliensterni,[4][8] such as those observed in the pleurocoels of the cervical vertebrae,[4] and in 2007, Martin Ezcurra and Gilles Cuny assigned it to its own genus, Lophostropheus.[3]

Paleobiology

Lophostropheus, as a coelophysoid, would have been a small to medium-sized bipedal carnivore,[9] probably comparable in size and habits to Liliensternus (best specimen estimated at 5.15 meters long, or 16.9 feet).[10] Very few dinosaurs are known from its time period; in fact, it is the only theropod genus known from good remains at the Triassic-Jurassic boundary.[3]

Paleoecology

Provenance and occurrence

The remains of the type specimen of Lophostropheus airelensis was recovered in the Airel Quarry locality of the Moon-Airel Formation, in Basse-Normandie, France. The specimen was collected by Pareyn in 1959 in sandy claystone and lenticular, sandy limestone that was deposited on the boundary of the Rhaetian stage of the Triassic period and the Hettangian stage of the Jurassic period, approximately 201-200 million years ago. It is one of the few dinosaurs known to have lived during the Triassic-Jurassic boundary. Lophostropheus is one of the few dinosaurs that may have survived the Triassic–Jurassic extinction event when at least half of the known species living on Earth became extinct. This specimen is housed in the collection of Caen University in Normandy, France, and has not been assigned a collection number.

See also

References

  1. ^ Liddell, Henry George and Robert Scott (1980). A Greek-English Lexicon (Abridged Edition). United Kingdom: Oxford University Press. ISBN 0-19-910207-4.
  2. ^ "LOPHOSTROPHEUS". Dinochecker.com. Retrieved 5 May 2013.
  3. ^ a b c d e f Ezcurra, Martin D.; Cuny, Gilles (2007). "The coelophysoid Lophostropheus airelensis, gen. nov.: a review of the systematics of "Liliensternus" airelensis from the Triassic-Jurassic boundary outcrops of Normandy (France)". Journal of Vertebrate Paleontology. 27 (1): 73–86. doi:10.1671/0272-4634(2007)27[73:TCLAGN]2.0.CO;2.
  4. ^ a b c Rauhut, Oliver W.M.; Hungerbühler, A. (2002). "A review of European Triassic theropods". Gaia. 15: 75–88.
  5. ^ Baron, M.G., Norman, D.B., and Barrett, P.M. (2017). A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature, 543: 501–506. doi:10.1038/nature21700
  6. ^ C., Larsonneur; and de Lapparent, Albert-Félix (1966). "Un dinosaurien carnivore, Halticosaurus, dans le Rhétien d'Airel (Manche)". Bulletin de la Société Linnéenne de Normandie (in French). 7: 108–117.
  7. ^ Cuny, Gilles; Galton, Peter M. (1993). "Revision of the Airel theropod dinosaur from the Triassic-Jurassic boundary (Normandy, France)". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 187 (3): 261–288.
  8. ^ Carrano, M. T., and Sampson, S. D., 2004, A review of coelophysoids (Dinosauria: theropoda) from the Early Jurassic of Europe, with comments on the late history of the coelophysoidea: Neues Jahrbuch für Geologie und Paläontologie, Monatschefte, 2004, n. 9, p. 537-558.
  9. ^ Tykoski, Ronald S.; Rowe, Timothy (2004). "Ceratosauria". In Weishampel, David B.; Dodson, Peter; Osmólska Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 47–70. ISBN 0-520-24209-2.
  10. ^ Paul, Gregory S. (1988). Predatory Dinosaurs of the World. New York: Simon & Schuster. p. 267. ISBN 0-671-61946-2.
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.

Coelophysoidea

Coelophysoidea were common dinosaurs of the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivorous forms with a superficial similarity to the coelurosaurs, with which they were formerly classified, and some species had delicate cranial crests. Sizes range from about 1 to 6 m in length. It is unknown what kind of external covering coelophysoids had, and various artists have portrayed them as either scaly or feathered. Some species may have lived in packs, as inferred from sites where numerous individuals have been found together.

Examples of coelophysoids include Coelophysis, Procompsognathus and Liliensternus. Most dinosaurs formerly referred to as being in the dubious taxon "Podokesauridae" are now classified as coelophysoids.

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.

Haya griva

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

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.

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.

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).

Unaysauridae

Unaysauridae is a family of basal sauropodomorphs from the Late Triassic of India and Brazil.

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.

Yueosaurus

Yueosaurus is an extinct genus of basal ornithopod dinosaur known from Zhejiang Province, China.

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