Amurosaurus (/əˌmʊəroʊˈsɔːrəs/; "Amur lizard") is a genus of lambeosaurine hadrosaurid dinosaur found in the latest Cretaceous period (66 million years ago) of eastern Asia. Like most lambeosaurs, it would have been a primarily bipedal herbivore with a "duckbill" shaped snout and a hollow crest on top of its head, although such a crest has not been found. Fossil bones of adults are rare, but an adult would most likely have been at least 6 metres (20 ft) long. According to Gregory S. Paul, it was about 8 metres (26 ft) long and weighed about 3,000 kilograms (6,600 lb).
|Replica skeleton, Brussels|
Bolotsky & Kurzanov, 1991
Bolotsky & Kurzanov, 1991
Russian paleontologists Yuri Bolotsky and Sergei Kurzanov first described and named this dinosaur in 1991. The generic name is derived from the Amur River and the Greek word sauros ("lizard"). The Amur (called Heilongjiang or "Black Dragon River" in Chinese) forms the border of Russia and China, and is near where this dinosaur's remains were found. There is one known species (A. riabinini), named in honor of the late Russian paleontologist Anatoly Riabinin, who conducted the first Russian expeditions to recover dinosaur remains in the Amur region in 1916 and 1917.
All fossils of Amurosaurus have been recovered from a single bonebed locality, discovered in 1984 within the city limits of Blagoveschensk in the Amur Oblast of far eastern Russia. This bonebed is found in the Udurchukan Formation, the oldest geologic formation in the Tsagayan Group of far eastern Russia and northeastern China. This formation is thought to belong to the Maastrichtian stage of the Late Cretaceous Period, and was deposited about 68 million years ago, or just prior to the Lancian faunal stage of North America. The sediments were laid down in the floodplain of a river, which transported the fossils, but only a short distance, judging by the randomly assorted, disarticulated, but well-preserved bones within the bonebed, including fragile skull elements. Only a small section of the bonebed has been uncovered, but 90% of the remains found so far belong to lambeosaurines like Amurosaurus, mostly juveniles, with the rest belonging to other taxa, such as the hadrosaurine Kerberosaurus. Theropod teeth are also abundant, and there are many toothmarks on the bones, made by predators or scavengers.
The holotype, or original specimen, consists of only a maxilla (upper jaw bone), and a dentary (lower jaw bone), both from the left side of the same individual. However, most of the other bones of the skull and skeleton have also been preserved in the bonebed, albeit of many different individuals. This other material was described more recently, making Amurosaurus the most abundant and completely known Russian dinosaur.
Amurosaurus is characterized by many autapomorphies, or unique features, of the skull, as well as the sigmoidal shape of the ulna (a lower arm bone) when viewed from the front or side. Most other known lambeosaurines have hollow crests on the top of their skulls, and although the bones that would make up such a crest are unknown in this dinosaur, the bones of the roof of the skull are modified to support one, so it can be assumed that Amurosaurus was crested as well.
As most of its features were described recently, as of early 2006, Amurosaurus has only been subjected to one cladistic analysis, which placed it as a basal member of the lambeosaurine subfamily of hadrosaurs, but more derived than either Tsintaosaurus or Jaxartosaurus.
All known basal lambeosaurines come from Asia, which has led to the hypothesis that lambeosaurines originated there and then later dispersed across the Bering Strait to North America. Two derived groups, the parasaurolophins (Parasaurolophus, Charonosaurus) and lambeosaurins (Corythosaurus, Nipponosaurus, Lambeosaurus, etc.) evolved later. As members of both groups are found in North America and Asia (And one from Europe, which one is not solidly known.), there must have been further dispersal after their evolution, although in which direction that dispersal occurred is still unclear.
The position of Amurosaurus in the evolutionary tree according to a 2013 study by Prieto-Márquez e.a. is indicated by this cladogram:
Anatoliy Riabinin was a Russian geologist and vertebrate paleontologist.
In the 1910s, Riabinin led the first paleontological expeditions to the Amur (in 1914 and 1916–17). The hadrosaurid Amurosaurus Riabinini is named for him. In 1925, he described the first dinosaur from China (though excavated in 1914). It initially bore the name Trachodon Amurense, though he renamed it Mandschurosaurus in 1930. He also conducted studies on fossilised turtles. In 1945, the genus now known as Riabininohadros was named for him.
His death date is sometimes given as 1942, though he was still active in the late 1940s (publications appeared in 1945 and 1946). He also described Batrachognathus in 1948.Ankylopollexia
Ankylopollexia is an extinct clade of ornithischian dinosaurs that lived from the Late Jurassic to the Late Cretaceous. It is a derived clade of iguanodontian ornithopods and contains the subgroup Styracosterna.
The name stems from the Greek word, “ankylos”, mistakenly taken to mean stiff, fused (in fact the adjective means bent or curved; used of fingers, it can mean hooked), and the Latin word, “pollex”, meaning thumb. Originally described in 1986 by Sereno, this most likely synapomorphic feature of a conical thumb spine defines the clade.First appearing around 156 million years ago, in the Jurassic, Ankylopollexia became an extremely successful and widespread clade during the Cretaceous, and were found around the world. The group died out at the end of the Maastrichtian. Even though they grew to be quite large, comparable to some carnivorous dinosaurs, they were universally herbivorous. Most ankylopollexians were bipedal.Aralosaurini
Aralosaurini is a tribe of basal lambeosaurine hadrosaurs endemic to Eurasia. It currently contains Aralosaurus (from the Aral sea of Kazakhstan) and Canardia (from Toulouse, Southern France).Arkharavia
Arkharavia is a dubious genus of somphospondylan sauropod, but at least some of the remains probably belong to a hadrosaurid. It lived in what is now Russia, during the Late Cretaceous. It was described in 2010 by Alifanov and Bolotsky. The type species is A. heterocoelica.Blasisaurus
Blasisaurus is a genus of lambeosaurine hadrosaurid dinosaur from the Late Cretaceous. It is known from a partial skull and skeleton found in late Maastrichtian-age rocks of Spain. The type species is Blasisaurus canudoi, described in 2010 by Penélope Cruzado-Caballero, Xabier Pereda-Suberbiola and José Ignacio Ruiz-Omeñaca, a group of researchers from Spain.Canardia
Canardia is an extinct genus of aralosaurin lambeosaurine dinosaur known from the Late Cretaceous Marnes d’Auzas Formation (late Maastrichtian stage) of Toulouse, Haute-Garonne Department, southern France. The type species Canardia garonnensis was first described and named by Albert Prieto-Márquez, Fabio M. Dalla Vecchia, Rodrigo Gaete and Àngel Galobart in 2013.Elasmaria
Elasmaria is a clade of iguanodont ornithopods known from Cretaceous deposits in South America, Antarctica, and Australia.Jaxartosaurus
Jaxartosaurus is a genus of hadrosaurid dinosaur similar to Corythosaurus which lived during the Late Cretaceous. Its fossils were found in Kazakhstan.Kazaklambia
Kazaklambia is an extinct genus of herbivorous lambeosaurine dinosaur known from the Late Cretaceous Dabrazinskaya Svita (Santonian stage) of southern Kazakhstan. It contains a single species, Kazaklambia convincens.Kazaklambia was first described in 1968 as a species of Procheneosaurus by Anatoly Konstantinovich Rozhdestvensky: Procheneosaurus convincens. The specific name refers to the fact that the specimen, the most complete dinosaur fossil ever discovered on Soviet territory, convincingly proved that dinosaurs could be found above the so-called "dinosaur horizon". After having for a time been referred to as Corythosaurus convincens, it was given its own genus in 2013 by Phil R. Bell and Kirstin S. Brink.Kazaklambia is known from a nearly complete skeleton of a juvenile missing only the snout, the front of the lower jaws, some dorsal vertebrae and end of the tail, holotype PIN 2230, found by G.A. Belenkiy in 1961. Although some studies considered it to be possibly synonymous with Jaxartosaurus aralensis, others found the species to be valid.Bell & Brink suggested that Kazaklambia is morphologically distinct from other Eurasian taxa and known juvenile lambeosaurines at a similar ontogenetic stage in having a prefrontal process of the postorbital with a thickened dome lateral to the frontal dome, doming of the nasal above and in front of the orbit, and a frontal length/width ratio of less than one.
Bell and Brink (2013) assigned Kazaklambia to the Lambeosaurinae, in a basal position. Morphometrics and morphological information suggest that Kazaklambia might be closely related to the basal lambeosaurines from Asia Amurosaurus and Tsintaosaurus, which was seen as proving an Asian origin of the Lambeosaurinae.Kerberosaurus
Kerberosaurus (meaning "Kerberos lizard") was a genus of saurolophine duckbill dinosaur from the late Maastrichtian-age Upper Cretaceous Tsagayan Formation of Blagoveshchensk, Amur Region, Russia (dated to 66 million years ago). It is based on bonebed material including skull remains indicating that it was related to Saurolophus and Prosaurolophus.Koshisaurus
Koshisaurus is a monospecific genus of basal hadrosauroid from the Kitadani Formation in Japan. The discovery of the genus suggests that hadrosauroids had higher diversity along the eastern margin of Asia in the Early Cretaceous. "Koshi" means an old Japanese regional name including Fukui prefecture where fossils of the genus were discovered.Kundurosaurus
Kundurosaurus is an extinct genus of saurolophine hadrosaurid dinosaur known from the Latest Cretaceous (probably Late Maastrichtian stage) of Amur Region, Far Eastern Russia. It contains a single species, Kundurosaurus nagornyi.Lambeosaurinae
Lambeosaurinae is a group of crested hadrosaurid dinosaurs.Lambeosaurini
Lambeosaurini, previously known as Corythosaurini, is one of four tribes of hadrosaurid ornithopods from the family Lambeosaurinae. It is defined as all lambeosaurines closer to Lambeosaurus lambei than to Parasaurolophus walkeri, Tsintaosaurus spinorhinus, or Aralosaurus tuberiferus, which define the other three tribes. Members of this tribe possess a distinctive protruding cranial crest. Lambeosaurins walked the earth for a period of around 12 million years in the Late Cretaceous, though they were confined to regions of modern day North America and Asia.Lapampasaurus
Lapampasaurus is an extinct genus of hadrosaurid known from the Late Cretaceous Allen Formation (late Campanian or early Maastrichtian stage) of La Pampa Province, Argentina. It contains a single species, Lapampasaurus cholinoi.The generic name refers to the Argentine province of La Pampa. The specific name honours the late collector José Cholino. The material includes cervical, dorsal, sacral and caudal vertebrae, the forelimb girdle, and the partial hindlimb.Magnapaulia
Magnapaulia is a genus of herbivorous lambeosaurine hadrosaurid dinosaurs known from the Latest Cretaceous Baja California, of northwestern Mexico. It contains a single species, Magnapaulia laticaudus. Magnapaulia was first described in 1981 as a possible species of Lambeosaurus by William J. Morris, and was given its own genus in 2012 by Prieto-Márquez and colleagues.Olorotitan
Olorotitan was a genus of lambeosaurine duckbilled dinosaur from the middle or latest Maastrichtian-age Late Cretaceous, whose remains were found in the Udurchukan Formation beds of Kundur, Amur Region, Far Eastern Russia. The type, and only species is Olorotitan arharensis.Plesiohadros
Plesiohadros is an extinct genus of hadrosauroid dinosaur. It is known from a partial skeleton including the skull collected at Alag Teg locality, from the Campanian Djadochta Formation of southern Mongolia. The type species is Plesiohadros djadokhtaensis.Xuwulong
Xuwulong is a genus of hadrosauroid dinosaur from the Early Cretaceous period. It lived during the early Cretaceous period (Aptian-Albian age) in what is now Yujingzi Basin in the Jiuquan area, Gansu Province of northwestern China. It is known from the holotype – GSGM F00001, an articulated specimen including a complete cranium, almost complete axial skeleton, and complete left pelvic girdle from Xinminpu Group. Xuwulong was named by You Hailu, Li Daqing and Liu Weichang in 2011 and the type species is Xuwulong yueluni.