Bactrosaurus (/ˌbæktroʊˈsɔːrəs/; meaning "Club lizard," "baktron" = club + sauros = lizard) is a genus of herbivorous dinosaur that lived in east China during the late Cretaceous, about 70 mya, though some Bactrosaurus fossils have been dated back to 90 mya. The position Bactrosaurus occupies in the Cretaceous makes it one of the earliest known hadrosauroids, and although it is not known from a full skeleton, Bactrosaurus is one of the best known of these forms of hadrosaurs predecessors.
|Partial B. johnsoni skeleton|
A typical Bactrosaurus would have been 6 metres (20 ft) long and 2 metres (6.6 ft) high when standing on all fours, and weighed 1.1 to 1.5 tonnes (2,400 to 3,300 lb), with an 80 centimetres (2.6 ft) femur.
It was an early relative of Lambeosaurus, perhaps a predecessor, as it shows a number of iguanodont-like features, including three stacked teeth for each visible tooth, small maxillary teeth, and an unusually powerful build for a hadrosaur. It shows features intermediate between those of the two main hadrosaurid groups, and may represent an ancestral form that evolved from an earlier iguanodontid dinosaur.
Bactrosaurus was originally described as lacking a crest, which would be typical for an iguanodont, but anomalously primitive for a lambeosaurine like itself. However subsequent study of Bactrosaurus remains uncovered pieces of what appear to be the base of an incompletely preserved crest.
In 2003, evidence of tumors, including hemangiomas, desmoplastic fibroma, metastatic cancer, and osteoblastoma was discovered in fossilized Bactrosaurus skeletons. Rothschild et al. tested dinosaur vertebrae for tumors using computerized tomography and fluoroscope screening. Several other hadrosaurids, including Brachylophosaurus, Gilmoreosaurus, and Edmontosaurus, also tested positive. Although more than 10,000 fossils were examined in this manner, the tumors were limited to Bactrosaurus and closely related genera. The tumors may have been caused by environmental factors or genetic propensity.
The first Bactrosaurus remains recovered from the Iren Dabasu Formation in the Gobi Desert of China were composed of partial skeletons of six individual B. johnsoni. The specimens collected appear to come from a variety of age groups, from individuals that may be hatchlings to full-sized adults. The fossils were described in 1933 by Charles W. Gilmore, who named the new animal Bactrosaurus, or "club lizard", in reference to the large club-shaped neural spines projecting from some of the vertebrae.
No complete remains have yet to be uncovered, but Bactrosaurus is still better known than most of the early hadrosaurs. Known parts of the anatomy of Bactrosaurus include the limbs, pelvis, and most of the skull (although the crest is notably absent).
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).Charles W. Gilmore
Charles Whitney Gilmore (March 11, 1874 – September 27, 1945) was an American paleontologist who gained renown in the early 20th century for his work on vertebrate fossils during his career at the United States National Museum (now the National Museum of Natural History). Gilmore named many dinosaurs in North America and Mongolia, including the Cretaceous sauropod Alamosaurus, Alectrosaurus, Archaeornithomimus, Bactrosaurus, Brachyceratops, Chirostenotes, Mongolosaurus, Parrosaurus, Pinacosaurus, Styracosaurus ovatus (now Rubeosaurus) and Thescelosaurus.Cionodon
Cionodon (meaning 'column tooth') was a dubious genus of dinosaur from the Late Cretaceous Period (Maastrichtian stage). The type species, Cionodon arctatus lived in what is now Colorado. It is classified as a hadrosaur, and was formally described by Edward Drinker Cope in 1874. It is a nomen dubium because it is based on very fragmentary remains. Two other species were described: Cionodon kysylkumensis from central Asia, and Cionodon stenopsis from what is now western Canada. Both are probably hadrosaurs, but are also fragmentary. Cionodon kysylkumensis has since been reclassified as Bactrosaurus kysylkumensis.Coniacian
The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded by the Turonian and followed by the Santonian.Dabrazhin Formation
The Dabrazhin Formation preserves dinosaur fossils in Kazakhstan. There are indeterminate remains of sauropods, nodosaurs, ornithomimosaurs, and other reptiles.
Gilmoreosaurus is the name given to a genus of dinosaur from the Cretaceous of Asia. The type species is Gilmoreosaurus mongoliensis. It is believed to be a hadrosaur or iguanodont from the Iren Dabasu Formation of Mongolia, dating to 70 Ma ago. Additional specimens have been described as distinct species, including G. atavus from the Khodzhakul Formation of Uzbekistan (120 Ma ago) and G. arkhangelskyi from the Bissekty Formation (89 Ma ago). However, these are based on very fragmentary remains, and their classification is dubious. An additional species, G. kysylkumensis (also from the Bissekty Formation) is sometimes included, though it has also been referred to the related genus Bactrosaurus.
The first Gilmoreosaurus fossil remains were collected by George Olsen in 1923 and consisted of disarticulated bones from several individuals at different localities. They were originally assigned to the genus Mandschurosaurus but later given the separate genus Gilmoreosaurus, which was characterized by its combination of basal iguanodontian and hadrosaurid traits. Although a consensus on the exact taxonomic placement of this genus remains unreached, a 2010 study by Prieto-Márquez and Norell places the animal in a closely related outgroup to Hadrosauridae, based on a reassessment of its taxonomic status using a large-sample phylogenic analysis.In 2003, evidence of tumors, including hemangiomas, desmoplastic fibroma, metastatic cancer, and osteoblastoma was discovered in fossilized Gilmoreosaurus skeletons. Rothschild et al. tested dinosaur vertebrae for tumors using computerized tomography and fluoroscope screening. Several other hadrosaurids, including Brachylophosaurus, Edmontosaurus, and Bactrosaurus, also tested positive. Although more than 10,000 fossils were examined in this manner, the tumors were limited to Gilmoreosaurus and closely related genera. The tumors may have been caused by environmental factors or genetic propensity.Glishades
Glishades is a genus of hadrosauroid dinosaur that lived in the Late Cretaceous in North America. It is based on AMNH 27414, two partial premaxillae discovered in the Upper Cretaceous rocks of the upper Two Medicine Formation in Montana, dated to about 74.5 million years ago. Cladistic analysis conducted by Prieto-Márquez suggests that Glishades is a non-hadrosaurid hadrosauroid, probably a sister taxon to Bactrosaurus johnsoni. The type species is Glishades ericksoni.According to Campione et al. (2012) the holotype specimen of Glishades ericksoni might actually be an indeterminate juvenile saurolophine hadrosaurid; these authors consider G. ericksoni to be a nomen dubium.Gobihadros
Gobihadros is a genus of basal hadrosauroid dinosaur from the Late Cretaceous of Mongolia. It contains one species, Gobihadros mongoliensis. The holotype specimen was recovered from the Bayan Shireh Formation (Cenomanian-Santonian). Its length was estimated at just under 3 meters (10 feet) long.Hadrosauroidea
Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or hadrosaurids, and all dinosaurs more closely related to them than to Iguanodon.They are from Asia, Europe and Africa. Many primitive hadrosauroids, such as the Asian Probactrosaurus and Altirhinus, have traditionally been included in a paraphyletic (unnatural grouping) "Iguanodontidae". With cladistic analysis, the traditional Iguanodontidae has been largely disbanded, and probably includes only Iguanodon and perhaps its closest relatives.Hadrosauromorpha
Hadrosauromorpha is a cohort of iguanodontian ornithopods, defined in 2014 by David B. Norman to divide Hadrosauroidea into the basal taxa with compressed manual bones and a pollex, and the derived taxa that lack them. The clade is defined as all the taxa closer to Edmontosaurus regalis than Probactrosaurus gobiensis. This results in different taxon inclusion depending on the analysis.Huehuecanauhtlus
Huehuecanauhtlus is an extinct genus of hadrosauroid dinosaur known from the Late Cretaceous (Santonian stage) of Michoacán, western Mexico. It contains a single species, Huehuecanauhtlus tiquichensis.Jeyawati
Jeyawati is a genus of hadrosauroid dinosaur which lived during the Turonian stage of the Late Cretaceous. The type species, J. rugoculus, was described in 2010, based on fossils recovered in the U.S. state of New Mexico.The holotype, MSM P4166, was discovered in the Moreno Hill Formation. A cladistic analysis indicates that Jeyawati was more plesiomorphic (ancestral) than Shuangmiaosaurus, Telmatosaurus, and Bactrosaurus, but more derived (less like the common ancestor) than Eolambia, Probactrosaurus, and Protohadros.Lambeosaurinae
Lambeosaurinae is a group of crested hadrosaurid dinosaurs.Levnesovia
Levnesovia is a genus of hadrosauroid dinosaur from the Late Cretaceous Bissekty Formation of Uzbekistan. It was related to Bactrosaurus. The type species is L. transoxiana. The genus name honours the late Russian paleontologist Lev Nesov, and the specific name refers to the ancient region Transoxiana. It is known from the minority of the skull and would have reached around two meters in length.Probactrosaurus
Probactrosaurus (meaning "before Bactrosaurus") is an early herbivorous hadrosauroid iguanodont dinosaur. It lived in Mongolia and China during the Late Cretaceous period.Tanius
Tanius (meaning "of Tan") is a genus of hadrosauroid dinosaur. It lived in the Late Cretaceous of China. The type species, named and described in 1929 by Carl Wiman, is Tanius sinensis. The generic name honours the Chinese paleontologist Tan Xichou ("H.C. Tan"). The specific epithet refers to China. In 2010 Gregory S. Paul estimated the length of Tanius at seven metres and the weight at two tonnes.Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by the Cenomanian stage and underlies the Coniacian stage.At the beginning of the Turonian an anoxic event took place which is called the Cenomanian-Turonian boundary event or the "Bonarelli Event".Yunganglong
Yunganglong is an extinct genus of basal hadrosauroid dinosaur known from the early Late Cretaceous lower Zhumapu Formation of Zuoyun County, Shanxi Province of northeastern China. It contains a single species, Yunganglong datongensis.Zhanghenglong
Zhanghenglong is an extinct genus of herbivorous hadrosauroid iguanodont dinosaur known from the Late Cretaceous (middle Santonian stage) Majiacun Formation in Xixia County of Henan Province, China. It contains a single species, Zhanghenglong yangchengensis, represented by a disarticulated and partial cranium and postcranial skeleton.