Rapator

Rapator is a genus of theropod dinosaur from the Griman Creek Formation of New South Wales, Australia, dating to the Albian age of the early Cretaceous period, 105 million years ago.[1] It contains only the type species, Rapator ornitholestoides, which was originally named by Friedrich von Huene in 1932.[2]

Rapator
Temporal range: Early Cretaceous, 105 Ma
Manual bone
Illustration of the holotype manual bone
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Clade: Megaraptora
Genus: Rapator
Huene, 1932
Type species
Rapator ornitholestoides
Huene, 1932

Description

The holotype and only known specimen, BMNH R3718, consists of a single left hand bone, discovered around 1905 near Wollaston, on the Lightning Ridge.[3] The fossil has been opalised.[3] The bone has a length of seven centimetres.[2] This manual element shows a prominent dorsomedial process, a feature shared with the much smaller Ornitholestes which occasioned the specific name.[3] The process with Ornitholestes is much less distinctive though.[3] On its upper end there is only one cotyle, from which von Huene deduced it must have been a metacarpal.[2] However, several coelurosaurian groups lack a second cotyle on the first phalanx also. If Rapator had a build like Australovenator, it would have attained a considerable size: a body length of nine metres (30 ft) has been estimated.[3] Remains of a megaraptorid, referred to by the public media as "Lightning Claw," discovered in opal fields southwest of Lightning Ridge, Australia, may well represent more material of Rapator.[4]

Classification

The type specimen of Rapator was originally described as a metacarpal I, a bone from the upper part of a theropod's hand.[2] It was later noted that the bone is similar to a finger bone, the first phalanx of the first finger, of an alvarezsaur[5] or of a primitive coelurosaurian similar to Nqwebasaurus.[6] With the discovery of Australovenator, which had a similar metacarpal, Rapator was recognized as a probable megaraptoran. In fact, Australovenator and Rapator differ only in some small details of the bone and may be synonyms, though Agnolin and colleagues in 2010 considered Rapator a dubious genus (nomen dubium) due to its fragmentary nature.[7] However, White et al. found differences between the hand bone of Rapator and the equivalent bone of Australovenator, supporting the distinction between the two. They also noted that the two genera come from formations separated chronologically by about 10 million years, making them unlikely to be synonymous.[1]

Rapator has been synonymised with Walgettosuchus, a theropod found in the same formation.[8] As the latter is only known from a caudal vertebra, the identity cannot be proven.

Etymology

The meaning of the generic name is problematic. Von Huene gave no etymology.[2] "Rapator" does not exist in Classical Latin and occurs only very rarely in Mediaeval Latin with the meaning "violator".[9] One possible explanation is that von Huene, having been influenced by Latin raptare, "to plunder",[10] mistakenly thought such a word actually existed with the meaning of "plunderer".[11] It has also been considered a simple misspelling of, or confusion with, raptor, "seizer" or "thief".[3] The specific name means "resembling Ornitholestes".

References

  1. ^ a b White, M. A.; Falkingham, P. L.; Cook, A. G.; Hocknull, S. A.; Elliott, D. A. (2013). "Morphological comparisons of metacarpal I forAustralovenator wintonensisandRapator ornitholestoides: Implications for their taxonomic relationships". Alcheringa: An Australasian Journal of Palaeontology. 37 (4): 435–441. doi:10.1080/03115518.2013.770221.
  2. ^ a b c d e Huene, F. von. (1932). Die fossile Reptil-Ordnung Saurischia, ihre Entwicklung und Geschichte. Monogr. Geol. Pal. 4 (1) pts. 1 and 2, viii + 361 pp.
  3. ^ a b c d e f Long, J.A. (1998). Dinosaurs of Australia and New Zealand and Other Animals of the Mesozoic Era, Harvard University Press, p. 104
  4. ^ Bell, P. R., Cau, A., Fanti, F., & Smith, E. (2015). A large-clawed theropod (Dinosauria: Tetanurae) from the Lower Cretaceous of Australia and the Gondwanan origin of megaraptorid theropods. Gondwana Research.
  5. ^ Holtz, Molnar, and Currie (2004). "Basal Tetanurae." In Weishampel, Dodson and Osmolska (eds.), The Dinosauria Second Edition. University of California Press. 861 pp.
  6. ^ Salisbury, Agnolin, Ezcurra, and Pias (2007). "A critical reassessment of the Cretaceous non-avian dinosaur faunas of Australia and New Zealand." Journal of Vertebrate Paleontology, 27(3): 138A.
  7. ^ Agnolin, Ezcurra, Pais and Salisbury, (2010). "A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: Evidence for their Gondwanan affinities." Journal of Systematic Palaeontology, 8(2): 257-300.
  8. ^ Steel, R. (1970) Handbuch der Paläoherpetologie/Encyclopedia of Paleoherpetology. Part 14. Saurischia. Gustav Fischer Verlag, Stuttgart 1-87
  9. ^ Tombeur, Paul. (1998) Thesaurus formarum totius Latinitatis a Plauto usque ad saeculum XXum : TF. CETEDOC, Universitas Catholica Lovaniensis, Lovanii Novi
  10. ^ https://web.archive.org/web/20100920040121/http://dinosauria.com/dml/names/dinor.htm Dinosauria Translation and Pronunciation Guide, retrieved 28-09-2010
  11. ^ Lambert, D. (1991) The Dinosaur Data Book: the definitive illustrated encyclopedia of dinosaurs and other prehistoric reptiles. Gramercy Books. p. 89

External links

1932 in paleontology

Paleontology or palaeontology 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 1932.

Aerosteon

Aerosteon is a genus of megaraptoran dinosaur from the Late Cretaceous period of Argentina. Its remains were discovered in 1996 in the Anacleto Formation, dating to the Santonian stage (about 84 million years ago). The type and only known species is A. riocoloradense. Its specific name indicates that its remains were found 1 km (0.6 miles) north of the Río Colorado, in Mendoza Province, Argentina.

They show evidence of a bird-like respiratory system. Aerosteon's name can be translated as air bone and derives from Greek ἀήρ (aer, "air") and ὀστέον (osteon, "bone"). Though the species name was originally published as "riocoloradensis", Greek ὀστέον is neuter gender, so according to the ICZN the species name must be riocoloradense to match.

Alvarezsauridae

Alvarezsauridae is a family of small, long-legged dinosaurs. Although originally thought to represent the earliest known flightless birds, a consensus of recent work suggests that they evolved from an early branch of maniraptoran theropods. Alvarezsaurids were highly specialized. They had tiny but stout forelimbs, with compact, bird-like hands. Their skeletons suggest that they had massive breast and arm muscles, possibly adapted for digging or tearing. They had long, tube-shaped snouts filled with tiny teeth. They may have been adapted to prey on colonial insects such as termites.

Alvarezsaurus, the type genus of the family, was named for the historian Gregorio Álvarez

Australovenator

Australovenator (meaning "southern hunter") is a genus of megaraptorid theropod dinosaur from Cenomanian (Late Cretaceous)-age Winton Formation (dated to 95 million years ago) of Australia. It is known from partial cranial and postcranial remains which were described in 2009 by Scott Hocknull and colleagues, although additional descriptions and analyses continue to be published. It is the most complete predatory dinosaur discovered in Australia.

Griman Creek Formation

The Griman Creek Formation is a geological formation in northern New South Wales and southern Queensland, Australia whose strata date back to the Albian to Cenomanian. Dinosaur remains are among the fossils that have been recovered from the formation.

List of Australian and Antarctic dinosaurs

This is a list of dinosaurs whose remains have been recovered from Australia or Antarctica.

List of dinosaur genera

This list of dinosaurs is a comprehensive listing of all genera that have ever been included in the superorder Dinosauria, excluding class Aves (birds, both living and those known only from fossils) and purely vernacular terms.

The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomen dubium), or were not formally published (nomen nudum), as well as junior synonyms of more established names, and genera that are no longer considered dinosaurs. Many listed names have been reclassified as everything from birds to crocodilians to petrified wood. The list contains 1559 names, of which approximately 1192 are considered either valid dinosaur genera or nomina dubia.

Megaraptora

Megaraptora is a clade of carnivorous theropod dinosaurs with elongated hand claws and controversial relations to other theropods.Megaraptorans are incompletely known, and no complete megaraptoran skeleton has been found. However, they still possessed a number of unique features. Their forelimbs were large and strongly built, and the ulna bone had a unique shape in members of the family Megaraptoridae, a subset of megaraptorans which excludes Fukuiraptor. The first two fingers were elongated, with massive curved claws, while the third finger was small. Megaraptoran skull material is very incomplete, but a juvenile Megaraptor described in 2014 preserved a portion of the snout, which was long and slender. Leg bones referred to megaraptorans were also quite slender and similar to those of coelurosaurs adapted for running. Although megaraptorans were thick-bodied theropods, their bones were heavily pneumatized, or filled with air pockets. The vertebrae, ribs, and the ilium bone of the hip were pneumatized to an extent which was very rare among theropods, only seen elsewhere in taxa such as Neovenator. Other characteristic features include opisthocoelous neck vertebrae and compsognathid-like teeth.The clade was originally named in 2010 as a subset of the family Neovenatoridae, a group of lightly-built allosauroids related to the massive carcharodontosaurids such as Giganotosaurus and Carcharodontosaurus. A 2013 phylogenetic analysis by Fernando Novas and his colleagues disagreed with this classification scheme, and instead argued that the megaraptorans evolved deep within Tyrannosauroidea, a superfamily of basal coelurosaurs including the famous Tyrannosaurus. Subsequent refinements to Novas's data and methodologies have supported a third position for the group, at the base of Coelurosauria among other controversial theropods such as Gualicho, but not within the Tyrannosauroidea. Regardless of their position, it is clear that megaraptorans experienced a large amount of convergent evolution with either Neovenator-like allosauroids or basal coelurosaurs.Megaraptorans were most diverse in the early Late Cretaceous of South America, particularly Patagonia. However, they had a widespread distribution. Fukuiraptor, the most basal ("primitive") known member of the group, lived in Japan. Megaraptoran material is also common in Australia, and the largest known predatory dinosaur from the continent, Australovenator, was a megaraptoran.

Neovenator

Neovenator (nee-o-ven-a-tor) which means "new hunter" is a genus of allosauroid dinosaur. At the time of its discovery on the Isle of Wight, United Kingdom, it was the best-known large carnivorous dinosaur from the Early Cretaceous (Hauterivian-Barremian) of Europe.

South Polar region of the Cretaceous

The South Polar region of the Cretaceous comprised the continent of East Gondwana–modern day Australia and Antarctica–a product of the break-up of Gondwana. The southern region, during this time, was much warmer than it is today, ranging from perhaps 4–8 °C (39–46 °F) in the latest Cretaceous Maastrichtian in what is now southeastern Australia. This prevented permanent ice sheets from developing and fostering polar forests, which were largely dominated by conifers, cycads, and ferns, and relied on a temperate climate and heavy rainfall. Major fossil-bearing geological formations that record this area are: the Santa Marta and Sobral Formations of Seymour Island off the Antarctic Peninsula; the Snow Hill Island, Lopez de Bertodano, and the Hidden Lake Formations on James Ross Island also off the Antarctic Peninsula; and the Eumeralla and Wonthaggi Formations in Australia.

The South Polar region housed many endemic species, including several relict forms that had gone extinct elsewhere by the Cretaceous. Of the dinosaur assemblage, the most diverse were the small hypsilophodont-like dinosaurs. The South Polar region also was home to the last labyrinthodont amphibian, Koolasuchus. The isolation of Antarctica produced a distinct ecosystem of marine life called the Weddellian Province.

Walgettosuchus

Walgettosuchus (meaning "Walgett crocodile") is currently thought to be an invalid genus of theropod dinosaur.

An opalised vertebra of a theropod dinosaur was found before 1909 by T.C. Wollaston in an opal bearing sandstone at Lightning Ridge near Walgett, in New South Wales. The fossil was sent to the British Museum of Natural History and was reported in January 1909 by Arthur Smith Woodward.In 1932 the type species Walgettosuchus woodwardi was named by Friedrich von Huene, based on this vertebra. The generic name is derived from the town of Walgett and Soukhos, the Greek name of the Egyptian crocodile god Sobek. During the 1930s Von Huene tended to form dinosaur names with the ending ~suchus instead of ~saurus because of the closer relationship to crocodiles than to lizards. The specific name honours Woodward.

The holotype, BMNH R3717, was found in the Albian-age Lower Cretaceous Griman Creek Formation. It consists of a 63-millimetre-long (2.5 in) incomplete amphicoelous (concave surfaces for articulation on the anterior and posterior faces) caudal vertebral centrum. For unknown reasons, he believed it had elongate prezygapophyses. He also suggested that if more material was known, it could prove to be synonymous with other Lightning Ridge "coelurosaurs" (i.e. Rapator; coelurosaur in the outdated sense of any small theropod).Von Huene assigned Walgettosuchus to the Ornithomimidae. In his 1990 review, Ralph Molnar noted that the type cannot be distinguished from tail vertebrae from ornithomimids or allosaurids, and considered it to be an indeterminate theropod and a nomen dubium or (more likely) an invalid taxon.

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