Concavenator | |
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Type specimen | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | † Carcharodontosauridae |
Genus: | † Concavenator Ortega et al. 2010 |
Species: | †C. corcovatus |
Binomial name | |
†Concavenator corcovatus Ortega et al. 2010 | |
Concavenator is an extinct allosaurinae|allosaurid]] theropod dinosaur that lived approximately 130 million years ago during the Early Cretaceous period (Barremian age). The type species is C. corcovatus. Concavenator corcovatus means "Cuenca hunter with a hump". [2] The fossil was discovered in the Las Hoyas fossil site of Spain by paleontologists José Luis Sanz, Francisco Ortega, and Fernando Escaso from the Autonomous University of Madrid [3] and the National University of Distance Education. [2]
Concavenator was a medium-sized advanced allosaurid, reaching 5–6 m (16–20 ft) long and 320–400 kg (710–880 lb). [4] [5] [6] It possessed several unique features, including the two extremely tall vertebrae in front of the hips that formed a tall, narrow, pointed crest (possibly supporting a hump) on the dinosaur's back. [7] The function of such crests, however, is currently unknown. Paleontologist Roger Benson from the University of Cambridge speculated that one possibility is that "it is analogous to head-crests used in visual displays", but the Spanish scientists who discovered it noted it could also be a thermal regulator. [2]
Concavenator had structures resembling quill knobs on its ulna, a feature known only in birds and other feathered theropods, such as Velociraptor . Quill knobs are created by ligaments which attach to the feather follicle and, since scales do not form from follicles, the authors ruled out the possibility that they could indicate the presence of long display scales on the arm. Instead, the knobs have been thought to probably anchor simple, hollow, quill-like structures. Such structures are known both in coelurosaurs, such as Dilong, and in some ornithischians, like Tianyulong and Psittacosaurus . If the ornithischian quills are homologous with bird feathers, their presence in Concavenator and other allosauroids would be expected. [7] However, if ornithischian quills are not related to feathers, the presence of these structures in Concavenator would show that feathers had begun to appear in earlier, more primitive forms than coelurosaurs.
Feathers or related structures would then likely be present in the first members of the clade Neotetanurae, which lived in the Middle Jurassic. No impressions of any kind of integument were found near the arm, although extensive scale impressions were preserved on other portions of the body, including broad, rectangular scales on the underside of the tail, bird-like scutes on the feet, and plantar pads on the undersides of the feet. [7]
However, the significance of the 'quill knobs' remains controversial, as some amount of skepticism has been raised among experts on the validity of the interpretation that the ulnar bumps represent quill knobs. [8] Christian Foth and colleagues noted that the quill knobs of Concavenator were on the anterolateral side of the ulna. They suggest they were intermuscular lines that acted as tendon attachments. [9] The hypothesis that the bumps along the ulna represented muscular insertion points or ridges was subsequently examined and the results were presented at the 2015 meeting of the Society of Vertebrate Paleontology. Elena Cuesta Fidalgo, along with two of the researchers who initially described Concavenator (Ortega and Sanz), attempted to reconstruct its forearm musculature to determine if the ulnar bumps would be explained as an inter-muscular ridge. They identified the insertion point for the major arm muscles and determined that the row of bumps could not have been located between any of them. They found that the only possibility was that the bumps could be an attachment scar for the M. anconeus muscle. However, this is unlikely because this muscle normally attaches to a smooth surface without marks or bumps on the underlying bone. They argued that the most likely explanation for the bumps was their initial interpretation as feather quill knobs. The authors admitted that it was unusual for quill knobs to form along the posterolateral surface of the bone, but also noted that the same arrangement is found in some modern birds, like the Moorhen. [10]
In 2018, Cuesta Fidalgo published her doctorate thesis on the anatomy of Concavenator, which argued that the ulna was preserved in lateral view. This means that the ulnar bumps were positioned posterolaterally instead of anterolaterally as Cau and Mortimer claimed. Cuesta Fidalgo noted that the proximal part of the ulna is affected by fracturing and abrasion, with certain features that would have shifted when compared to their position in the bone while the animal was alive. For example, in the fossil, the lateral process of the ulna is positioned further posteriorly than the ulnar bumps. In Allosaurus and Acrocanthosaurus, the lateral process is on the lateral (rather than posterior) part of the bone, which would seem to support the ulnar bumps being anterolateral in position if the lateral process was truly preserved in lateral orientation in Concavenator. However, Cuesta Fidalgo described how the lateral process was distorted posteriorly when compared to the bumps and was not valid evidence for the claim that the ulna had shifted into anterior view. The ulna's distortion (as well as genus-specific proportions) means that precise comparisons to Allosaurus and Acrocanthosaurus would be misleading. [11] As Cuesta Fidalgo and her colleagues explained in 2015, the ulnar bumps could not be an intermuscular line if the bone is preserved in lateral view. [10] Cuesta Fidalgo and her colleagues pointed out that these bumps on the ulna are posterolateral, which is unlike that of interosseous ligaments. [12]
The following cladogram after Novas et al., 2013, shows its place within allosaurinae. [13]
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Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and a premier example of a complex evolutionary novelty. They are among the characteristics that distinguish the extant birds from other living groups.
The pennaceous feather is a type of feather present in most modern birds and in some other species of maniraptoriform dinosaurs.
Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.
Ornithomimosauria are theropod dinosaurs which bore a superficial resemblance to the modern-day ostrich. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia, as well as Africa and possibly Australia. The group first appeared in the Early Cretaceous and persisted until the Late Cretaceous. Primitive members of the group include Nqwebasaurus, Pelecanimimus, Shenzhousaurus, Hexing and Deinocheirus, the arms of which reached 2.4 m (8 feet) in length. More advanced species, members of the family Ornithomimidae, include Gallimimus, Struthiomimus, and Ornithomimus. Some paleontologists, like Paul Sereno, consider the enigmatic alvarezsaurids to be close relatives of the ornithomimosaurs and place them together in the superfamily Ornithomimoidea.
Avimimus, meaning "bird mimic", is a genus of oviraptorosaurian theropod dinosaur, named for its bird-like characteristics, that lived in the late Cretaceous in what is now Mongolia, around 85 to 70 million years ago.
Afrovenator is a genus of megalosaurid theropod dinosaur from the Middle or Late Jurassic Period on the Tiourarén Formation and maybe the Irhazer II Formation of the Niger Sahara region in northern Africa. Afrovenator represents the only properly identified Gondwanan megalosaur, with proposed material of the group present in the Late Jurassic on Tacuarembó Formation of Uruguay and the Tendaguru Formation of Tanzania.
Carcharodontosauridae is a group of carnivorous theropod dinosaurs. In 1931, Ernst Stromer named Carcharodontosauridae as a family, which, in modern paleontology, indicates a clade within Carnosauria. Carcharodontosaurids include some of the largest land predators ever known: Giganotosaurus, Mapusaurus, Carcharodontosaurus, and Tyrannotitan all rivaled Tyrannosaurus in size. Estimates give a maximum weight of 8–10 metric tons for the largest carcharodontosaurids, while the smallest carcharodontosaurids were estimated to have weighed at least 500 kilograms (1,100 lb).
Altispinax is a genus of large predatory theropod dinosaur from the Early Cretaceous period of what is now the Wadhurst Clay Formation of East Sussex, England.
Pelecanimimus is an extinct genus of basal ("primitive") ornithomimosaurian dinosaur from the Early Cretaceous of Spain. It is notable for possessing more teeth than any other member of the Ornithomimosauria, most of which were toothless.
Ceratosauridae is an extinct family of theropod dinosaurs belonging to the infraorder Ceratosauria. The family's type genus, Ceratosaurus, was first found in Jurassic rocks from North America. Ceratosauridae is made up of the genera Ceratosaurus, found in North America, Tanzania, and Portugal, and Genyodectes, from the Early Cretaceous of Argentina. Unnamed probable ceratosaurids are known from limited material in the Middle Jurassic of Madagascar, the Late Jurassic of Switzerland, the Late Jurassic of Tanzania, and the Late Jurassic or possibly Early Cretaceous of Uruguay.
Velociraptorinae is a subfamily of the theropod group Dromaeosauridae. The earliest velociraptorines are probably Nuthetes from the United Kingdom, and possibly Deinonychus from North America. However, several indeterminate velociraptorines have also been discovered, dating to the Kimmeridgian stage, in the Late Jurassic Period. These fossils were discovered in the Langenberg quarry, Oker near Goslar, Germany.
Similicaudipteryx, meaning "similar to Caudipteryx", is a genus of theropod dinosaur of the family Caudipteridae.
The La Huérguina Formation is a geological formation in Spain whose strata date back to the Barremian stage of the Early Cretaceous. Las Hoyas is a Konservat-Lagerstätte within the formation, located near the city of Cuenca, Spain. The site is mostly known for its exquisitely preserved dinosaurs, especially enantiornithines. The lithology of the formation mostly consists of lacustrine limestone deposited in a freshwater wetland environment.
Sciurumimus is an extinct genus of tetanuran theropod from the Late Jurassic of Germany. It is known from a single juvenile specimen representing the type species, Sciurumimus albersdoerferi, which was found in a limestone quarry close to Painten in Lower Bavaria. The specimen was preserved with traces of feather-like filaments.
Kulindadromeus was a herbivorous dinosaur, a basal neornithischian from the Middle Jurassic. The first Kulindadromeus fossil was found in Russia. Its feather-like integument is evidence for protofeathers being basal to Ornithischia and possibly Dinosauria as a whole, rather than just to Coelurosauria, as previously suspected.
Dakotaraptor is a potentially chimaeric or dubious genus of large dromaeosaurid theropod dinosaur that lived in western North America during the Late Cretaceous period. The remains have been found in the Maastrichtian-aged Hell Creek Formation, dated to the very end of the Mesozoic era, making Dakotaraptor one of the last surviving dromaeosaurids. The remains of D. steini were discovered in a multi-species bonebed. Elements of the holotype and referred specimens were later found to belong to trionychid turtles and further analysis of potential non-dromaeosaurid affinities of the holotype and referred material have not yet been conducted. Phylogenetic analyses of D. steini place it in a variety of positions within Dromaeosauridae.
The year 2018 in non-avian dinosaur paleontology was eventful. Archosaurs include the only living dinosaur group — birds — and the reptile crocodilians, plus all extinct dinosaurs, extinct crocodilian relatives, and pterosaurs. Archosaur palaeontology is the scientific study of those animals, especially as they existed before the Holocene Epoch began about 11,700 years ago. This article records new taxa of fossil archosaurs of the non-avian variety that have been described during the year 2018, as well as other significant discoveries and events related to paleontology of archosaurs that occurred in the year 2018.