Probactrosaurus
Encyclopedia
Bactrosaurus
Bactrosaurus is a genus of herbivorous dinosaur that lived in east China during the late Cretaceous, about 70 mya. The position Bactrosaurus occupies in the Cretaceous makes it one of the earliest known hadrosaurs, and although it is not known from a full skeleton, Bactrosaurus is one of the best...
") is an early herbivorous hadrosauroid iguanodont
Iguanodont
Iguanodonts were herbivorous dinosaurs that lived from the mid-Jurassic to Late Cretaceous. Some members include Camptosaurus, Callovosaurus, Iguanodon, Ouranosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodonts were one of the first groups of dinosaurs to be found...
dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
. It lived in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
during the Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
period.
In 1959 and 1960 a Soviet-Chinese expedition uncovered the remains of a euornithopod in Inner-Mongolia near Moartu. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is Probactrosaurus gobiensis, described and named by A. K. Rozhdestvensky
Anatoly Konstantinovich Rozhdestvensky
Anatoly Konstantinovich Rozhdestvensky was a Russian paleontologist responsible for naming many dinosaurs, including Aralosaurus and Probactrosaurus....
in 1966
1966 in paleontology
-Newly named mesosaurs:-Newly named dinosaurs:Data courtesy of George Olshevsky's dinosaur genera list and Dr. Jeremy Montague's dinosaur genus database.-Non-mammalian:...
. The generic name refers to Rozhdestvensky's hypothesis that Probactrosaurus would be the direct ancestor of Bactrosaurus, a notion today discarded. The specific name refers to the Gobi desert
Gobi Desert
The Gobi is a large desert region in Asia. It covers parts of northern and northwestern China, and of southern Mongolia. The desert basins of the Gobi are bounded by the Altai Mountains and the grasslands and steppes of Mongolia on the north, by the Hexi Corridor and Tibetan Plateau to the...
. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen, PIN 2232/1, a partial skeleton with skull, was found in layers of the Dashuigou Formation
Dashuigou Formation
The Dashuigou Formation is a geological formation in Inner Mongolia, north China, whose strata date back to the Early Cretaceous period.Dinosaur remains are among the fossils that have been recovered from the formation.-Vertebrate paleofauna:...
. Another partial skeleton was found, PIN 2232-10, along with numerous other fragments.
In 1966 Rozhdestvensky also named a second species, Probactrosaurus alashanicus, based on fragmentary material. Its specific name refers to the Alxa League
Alxa League
Alxa League is one of 12 prefecture level divisions and three extant leagues of Inner Mongolia. The league borders Mongolia to the north, Bayan Nur to the northeast, Wuhai and Ordos to the east, Ningxia to the southeast, and Gansu to the south and west. The capital is Bayan Hot in the aimag's...
. In 2002 David Bruce Norman
David B. Norman
David Bruce Norman is a British paleontologist, currently Director of the Sedgwick Museum, Cambridge University. He is a fellow at Christ's College, Cambridge where he teaches geology in the Natural Sciences tripos. He is a member of the Palaeontological Association. He has studied Iguanodon...
published a revision of the genus, in which he reported the holotype specimen of P. alshanicus, the back of a skull, had been lost after being dispatched from Moscow
Moscow
Moscow is the capital, the most populous city, and the most populous federal subject of Russia. The city is a major political, economic, cultural, scientific, religious, financial, educational, and transportation centre of Russia and the continent...
to Beijing
Beijing
Beijing , also known as Peking , is the capital of the People's Republic of China and one of the most populous cities in the world, with a population of 19,612,368 as of 2010. The city is the country's political, cultural, and educational center, and home to the headquarters for most of China's...
. He concluded that the species was a synonym of P. gobiensis.
In 1997 Lü Junchang named a third species, Probactrosaurus mazongshanensis, based on holotype IVPP V.11333 found in 1992. The specific name refers to the Mazong Shan
Mazong Shan
The Mazong Shan is a minor mountain range of northern Gansu, between the Altay range to the north and the Qilian range to the south. The Mazong Shan peak rises to 2584 m....
region. Today, this form is seen as more closely related to Equijubus
Equijubus
Equijubus, meaning "horse mane" after the area in which it was found, is a genus of herbivorous hadrosauroid dinosaur from the Early Cretaceous of northwestern China.-Discovery and naming:...
and Altirhinus
Altirhinus
Altirhinus is a genus of iguanodontian ornithopod dinosaur from the Early Cretaceous Period of Mongolia.-Description:Altirhinus was herbivorous and bipedal when walking or running, but probably became quadrupedal when feeding from the ground. According to the original description, the entire body...
rather than to P. gobiensis and is therefore commonly referred to as "Probactrosaurus" mazongshanensis.
Probactrosaurus was a herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
dinosaur. In 2010 Gregory S. Paul
Gregory S. Paul
Gregory Scott Paul is a freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod dinosaurs and his detailed illustrations, both live and skeletal...
estimated the length at 5.5 metres (18 feet), the weight at one tonne. It was lightly built, with relatively long and slender arms and hands and only a small thumb spike. It had a narrow snout, an elongated lower jaw and tooth batteries, each consisting of a superimposed double row of flattened cheek teeth; a third row of replacement teeth was incipient. Probably predominantly quadrupedal, it shared some common features with the later duck-billed dinosaurs.
Probactrosaurus was originally assigned by Rozhdestvenky to the Iguanodontidae. Today it is seen as a basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
member of the Hadrosauroidea
Hadrosauroidea
Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or hadrosaurids, and their close relatives. Many primitive hadrosauroids, such as the sail-backed Ouranosaurus, have traditionally been included in a paraphyletic "Iguanodontidae"...
, relatively closely related to the Hadrosauridae.