Hirostenot (Greek).: Χιροστενοτεσ; lat.: Chirostenotes) is a genus of dinosaurs of the Upper Cretaceous period, a representative of the Theropods group (lat.: Theropoda), who lived in what is now North America. This genus belongs to the family Caenagnathida (lat.: Caenagnathidae) within the infraorder Oviraptosaurs (Oviraptorosauria).
Fossils of the type species Chirostenotes pergracillis, dating from the late Campanian and early Maastrichtian, have been found in the Dinosaur Park Formation.: Dinosaur Park Formation) in Alberta.
Along with Chirostenotes pergracillis, the species Chirostenotes elegans is also distinguished, which, however, may be a representative of another genus Elmisaurus (lat.: Elmisaurus), which was closely related to Chirostenote.
A large skeleton from the Horseshoe Canyon Formation was also assigned to the type species.: Horseshoe Canyon Formation), but in 2014 the dinosaur to which these bones belonged was separated into a separate genus Anzu (lat.: Anzu).
History of discovery and name
Back in 1924, fragmentary remains of a pair of forelimb hands of an unknown dinosaur were discovered, which the American paleontologist Charles Whitney Gilmore (eng.: Charles Whitney Gilmore) described by the Greek name Chirostenotes (“having narrow brushes”, or “thin-armed”).
In 1932, the foot bones of a dinosaur described by fossil collector Charles Mortram Sternberg were found.: Charles Mortram Sternberg) as Macrophalangia (lat.: Macrophalangia; “having big feet”).
Although later it was possible to prove that both of these finds had theropod characters, it was not clear whether they belonged to the same or two different species.
In 1936, the jaw of an unknown animal was found, which Sternberg described in 1940 and called caenagnath (lat.: Caenagnathus; “New Jaw”), and at first it was believed that the found jaw belonged to the bird. The family of priceprize, to which the chirostenot belongs, owes its name to the family of price.
In 1988, a skeleton found in 1923 was discovered and investigated in the collection of one museum. This skeleton indicates that all finds belong to the same genus of dinosaurs. Since then, all these different fossils appear under the single name “chirostenot”, since it was given to this genus earlier than others (the principle of priority of more old names in the biological nomenclature).
Previously, a pair of low jaws found with powerful teeth were also attributed to the chirostenot, but at present these bones are classified as belonging to the genus of Ricardeustaia (latch.: Ricardoestesia).
Anatomical features and type of power
Chirostenot was a bipedal theropod with a body length of about 2.9 meters. He, like some more primitive oviraptosaurs such as Caudipteryx (lat.: Caudipteryx) and Protarchaeopteryx (Protarchaeopteryx), theoretically could also be covered with feathers.
The long, narrow jaws of Chirostenoth have no teeth. Like some other representatives of the infraorder Oviraptosaurus, the skull of the Chirostenoth is characterized by the presence of a large ridge on it, resembling a horny outgrowth on the skull of a modern bird, the helmeted cassowary (lat.: Casuarius casuarius).
The metatarsus of this dinosaur is characterized by the so-called arctometatarsality, which occurs in various groups of “higher” theropods, in which the second and fourth metatarsal bones “compress” the upper end of the third (t.e. middle) metatarsal bone, resulting in only the lower end of the middle metatarsal bone being part of the dorsum of the foot. The metatarsus of the chirostenoth accounted for 22% of the length of its hind limb (without toes).
Little is known about the diet of this dinosaur: it may have been an omnivore or herbivore.
The classification of the genus Hirostenot was very confusing, primarily due to the fact that scientists initially attributed certain parts of the dinosaur body to different taxa. So, in 1924, Gilmore ranked him in the Celuridae family (lat.: Coeluridae).
Charles Sternberg believed that the genus Macrophalangia belonged to the Ornithomimidae family (lat.: Ornithomimidae), and later Chirostenot was assigned to the same family, although the American paleontologist John Harold Ostrom (eng.: John Harold Ostrom) considered him a member of the Dromaeosaurid family (lat.: Dromaeosauridae).
As for the tsenagnath described by Charles Sternberg, it was originally recognized as a bird. Even when it became clear in the 1970s that this was a representative of the infraorder Oviraptosaurs, the exact hierarchical position of this genus within the infraorder and the name “cenagnathus” remained controversial.
So, some paleontologists ranked this dinosaur among the elmisaurids (lat.: Elmisauridae) and oviraptorids (Oviraptoridae). However, since the late 1980s, most researchers have attributed it to a separate family of Caenagnathidae, and in some cases, to the subfamily of Caenagnathina (lat.: Caenagnathinae).