''Bactrosaurus'' (; meaning "Club lizard," "baktron" = club + ''sauros'' = lizard) is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

hadrosauroid 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''. Their remains have been recovered in Asia, Eu ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

that lived in

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

, about 96-85

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

. The position ''Bactrosaurus'' occupies in the Cretaceous makes it one of the earliest known

s, and although it is not known from a full skeleton, ''Bactrosaurus'' is one of the best known of these early hadrosauroids, making its discovery a significant finding.

Discovery

The first ''Bactrosaurus'' remains recovered from the

Iren Dabasu Formation The Iren Dabasu Formation (also known as Erlian Formation) is a Late Cretaceous geologic formation in the Iren Nor region of Inner Mongolia. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the fo ...

in the

Gobi Desert The Gobi Desert (Chinese: 戈壁 (沙漠), Mongolian: Говь (ᠭᠣᠪᠢ)) () is a large desert or brushland region in East Asia, and is the sixth largest desert in the world. Geography The Gobi measures from southwest to northeast an ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

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 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 N ...

, who named the new animal ''Bactrosaurus'', or "club lizard", in reference to the large club-shaped neural spines projecting from some of the vertebrae. The Iren Dabasu Formation has been dated to the

Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...

stage, around 95.8 ± 6.2

. 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)."Bactrosaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. ''The Age of Dinosaurs''. Publications International, LTD. p. 131. . "Bakesaurus" is an informal name based on a

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

from the

Majiacun Formation The Majiacun Formation is a Santonian to Coniacian geologic formation in China. * '' Zhanghenglong, Zhanghenglong yangchengensis''Xing et al., 2014 * Baryonychinae indet.? (possibly an indeterminate theropod due to no shared synapomorphies prese ...

of China assigned to ''Bactrosaurus'' in 2001. The ''nomen nudum'' was created and pictured in a Chinese-language book by Zhou (2005) and first surfaced on the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

during February 2006 when it was mentioned on the ''Dinosaur Mailing List'' by Jerry D. Harris.

Description

A typical ''Bactrosaurus'' would have been long and weighed . It was an early relative of ''

Lambeosaurus ''Lambeosaurus'' ( , meaning " Lambe's lizard") is a genus of hadrosaurid dinosaur that lived about 75 million years ago, in the Late Cretaceous period (Campanian stage) of North America. This bipedal/quadrupedal, herbivorous dinosaur is k ...

'' and shows a number of

iguanodont Iguanodontia (the iguanodonts) is a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include ''Camptosaurus'', ''Dryosaurus'', ''Iguanodon'', '' Tenontosaurus'', and the hadrosaurids or "duck-bil ...

-like features, including three stacked teeth for each visible tooth, small

ry teeth, and an unusually powerful build for a hadrosaur. It shows features intermediate between those of the two main hadrosaurid groups. Its femur measured long. ''Bactrosaurus'' was originally thought to be a

lambeosaurine Lambeosaurinae is a group of crested hadrosaurid dinosaurs. Classification Lambeosaurines have been traditionally split into the tribes or clades Parasaurolophini ('' Parasaurolophus'', ''Charonosaurus'', others (?).) and Lambeosaurini (''Cor ...

hadrosaurid, supposedly the oldest and most primitive known, and its crestless head was seen as an anomaly. A 1990 popular book suggested that it had an incompletely preserved crest, but recent studies place ''Bactrosaurus'' as a more basal

hadrosauromorph Hadrosauromorpha is a clade 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 a ...

. Basal members do not preserve hollow crests, so ''Bactrosaurus'' itself is likely to be crestless.

Paleobiology

In 2003, evidence of

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

s, including

hemangioma A hemangioma or haemangioma is a usually benign vascular tumor derived from blood vessel cell types. The most common form, seen in infants, is an infantile hemangioma, known colloquially as a "strawberry mark", most commonly presenting on the ski ...

desmoplastic fibroma In medicine, a desmoplastic fibroma is a benign, but locally aggressive, fibrous and rare tumor of the bone, affecting children and young adults, potentially resulting in cortical bone destruction. It usually affects craniofacial bones, mandible mo ...

metastatic cancer Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, the ...

, and

osteoblastoma Osteoblastoma is an uncommon osteoid tissue-forming primary neoplasm of the bone. It has clinical and histologic manifestations similar to those of osteoid osteoma; therefore, some consider the two tumors to be variants of the same disease, wit ...

was discovered in fossilized ''Bactrosaurus'' skeletons. Rothschild ''et al.'' tested dinosaur vertebrae for tumors using computerized tomography and

fluoroscope Fluoroscopy () is an imaging technique that uses X-rays to obtain real-time moving images of the interior of an object. In its primary application of medical imaging, a fluoroscope () allows a physician to see the internal structure and function ...

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.

References

{{Taxonbar, from=Q131247 Hadrosaurs Turonian life Late Cretaceous dinosaurs of Asia Fossils of Uzbekistan Bissekty Formation Fossil taxa described in 1933 Taxa named by Charles W. Gilmore Ornithischian genera

Discovery

Description

Paleobiology

See also

References