Dilong (dinosaur)

Dilong (dinosaur)

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Dilong is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of small tyrannosauroid
Tyrannosauroidea
Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period...

 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...

. The only species is Dilong paradoxus. It is from the Lower
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

 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...

 Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...

 near Lujiatun, Beipiao, in the western Liaoning
Liaoning
' is a province of the People's Republic of China, located in the northeast of the country. Its one-character abbreviation is "辽" , a name taken from the Liao River that flows through the province. "Níng" means "peace"...

 province of China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

. It lived about 130 million years ago. It was described by Xu Xing and colleagues in 2004.

The name is derived from the Chinese
Chinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...

 帝 meaning 'emperor' and 龙/龍 lóng meaning 'dragon'. "Di", "emperor", refers to the relationship of this animal to Tyrannosaurus rex
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...

, the "king" tyrannosaurid. "Long" is used to name Chinese dinosaurs in much the same way that the Latin -saur(us) is in the West. The specific name, paradoxus, is a Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

isation of the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 παράδοξον meaning 'against received wisdom'.

Description


The type specimen is IVPP 14243 (Institute of Vertebrate Paleontology and Paleoanthropology
Institute of Vertebrate Paleontology and Paleoanthropology
The Institute of Vertebrate Paleontology and Paleoanthropology of China is a prominent research institution and collections repository for fossils, including many dinosaur and pterosaurand cat poo specimens...

 in 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...

), a nearly complete, semi-articulated, skull and skeleton. Referred material includes IVPP 1242, a nearly complete skull and presacral vertebrae, TNP01109 (Tianjin Museum of Natural History), a partial skull, and IVPP V11579, another skull which may belong to D. paradoxus or may be a related species. The type specimen of Dilong was about 1.6 m in length, but it is thought to be a juvenile and may have been over 2 meters long when grown.

Feathers


See also Feathered dinosaurs
Feathered dinosaurs
The realization that dinosaurs are closely related to birds raised the obvious possibility of feathered dinosaurs. Fossils of Archaeopteryx include well-preserved feathers, but it was not until the early 1990s that clearly non-avialan dinosaur fossils were discovered with preserved feathers...


Dilong paradoxus had a covering of simple feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...

s or protofeathers. The feathers were seen in fossilized skin impressions from near the jaw
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...

 and tail. They are not identical to modern bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

 feathers, lacking a central shaft and most likely used for warmth, since they could not have enabled flight. Adult tyrannosaurs, found in Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...

 and Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...

 have skin impressions which appear to show the pebbly scales typical of other dinosaurs. Xu et al. (2004) speculated that the tyrannosauroids may have had different skin coverings on different parts of their bodies - perhaps mixing scales and feathers. They also speculated that feathers may correlate negatively with body size - that juveniles may have been feathered, then shed the feathers and expressed only scales as the animal became larger and no longer needed insulation to stay warm.

Classification


When Dilong was first described, it was considered one of the earliest and most primitive members of Tyrannosauroidea
Tyrannosauroidea
Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period...

, the group that includes the later, larger tyrannosaurids
Tyrannosauridae
Tyrannosauridae is a family of coelurosaurian theropod dinosaurs which comprises two subfamilies containing up to six genera, including the eponymous Tyrannosaurus. The exact number of genera is controversial, with some experts recognizing as few as three...

 such as Tyrannosaurus rex. At least one later study, by Turner and colleagues in 2007, reanalyzed the relationships of coelurosaurian dinosaurs, including Dilong, and found that it was not a tyrannosauroid. Rather, they placed Dilong two steps above the tyrannosauroids in their phylogeny; more advanced than Coelurus
Coelurus
Coelurus is a genus of coelurosaur dinosaur from the Late Jurassic period . The name means "hollow tail", referring to its hollow tail vertebrae...

, but more primitive than the Compsognathidae
Compsognathidae
Compsognathidae is a family of small carnivorous dinosaurs, generally conservative in form, from the Jurassic and Cretaceous Periods. Compsognathids lie at or near the origin of feathers—skin impressions are known from four genera, Compsognathus, Sinosauropteryx, Sinocalliopteryx, and Juravenator...

. However, other studies continued to find Dilong as a tyrannosauroid, and some (such as Carr & Williamson 2010) found Dilong to fall within Tyrannosauroidea, not among the more advanced coelurosaurs.

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