''Tsaagan'' (meaning "white") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

dromaeosaurid Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

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 ...

from the

Djadokhta Formation The Djadochta Formation (sometimes transcribed and also known as Djadokhta, Djadokata, or Dzhadokhtskaya) is a highly fossiliferous geological formation situated in Central Asia, Gobi Desert, dating from the Late Cretaceous period, about 75 mill ...

of 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'', ...

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million ...

Discovery and naming

The holotype of ''Tsaagan'' was discovered in 1996 and first identified as a specimen of ''

Velociraptor ''Velociraptor'' (; ) is a genus of small dromaeosaurid dinosaur that lived in Asia during the Late Cretaceous epoch, about 75 million to 71 million years ago. Two species are currently recognized, although others have been assigned in th ...

''. After a CAT-scan in May 1998 it was concluded that it represented a new genus. In December 2006 its

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specim ...

was named and described by Mark Norell, James Clark, Alan Turner, Peter Makovicky,

Rinchen Barsbold , Rinchyengiin Barsbold, born December 21, 1935 in Ulaanbaatar) is a Mongolian paleontologist and geologist. He works with the Institute of Geology, at Ulaanbaatar, Mongolia. He is an expert in vertebrate paleontology and Mesozoic stratigraphy. Bar ...

and Timothy Rowe. The

species name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

, ''Tsaagan mangas'', should be read as a whole with the generic name qualifying the

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bo ...

, and is derived from the Mongolian words for "white monster" (), although with an accidental misspelling of the word Tsagaan. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

specimen, IGM 100/1015, was found near Xanadu in

Ömnögovi Province Ömnögovi ( mn, Өмнөговь ''Ömnögovǐ'', ''South Gobi'') is an aimag (province) of Mongolia, located in the south of the country, in the Gobi Desert. Ömnögovi is Mongolia's largest aimag. The capital is Dalanzadgad. The province is ...

in layers of the Djadokhta Formation dating to the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

, about 75 million years ago. It consists of a well-preserved skull and series of ten neck vertebrae as well as a damaged left shoulder girdle. It is the only specimen found of ''Tsaagan'' and belonged to an adult individual.

Description

''Tsaagan'' was a medium-sized dromaeosaurid. In 2010 Gregory S. Paul estimated its length at , its weight at . The skull in general appearance resembles that of ''Velociraptor'' but differs from it in many details. It is more robust and smooth on top; unique derived traits,

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

, include long paroccipital processes and basipterygoids at the back of the skull and a

jugal The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anatomy ...

touching the

squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...

Classification

''Tsaagan'' is a member of the group

Dromaeosauridae Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

. A

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

analysis by Norell ''et al.'' originally indicated it was more precisely a member of the

Velociraptorinae Velociraptorinae is a subfamily of the theropod group Dromaeosauridae. The earliest velociraptorines are probably ''Nuthetes'' from the United Kingdom, and possibly '' Deinonychus'' from North America. However, several indeterminate velociraptor ...

. In 2010 an analysis showed it was closely related to ''

Linheraptor ''Linheraptor'' is a genus of dromaeosaurid dinosaur which lived in what is now China in the Late Cretaceous. It was named by Xu Xing and colleagues in 2010, and contains the species ''Linheraptor exquisitus''. This bird-like dinosaur was less t ...

''; subsequently Senter (2011) and Turner, Makovicky and Norell (2012) argued that ''Linheraptor exquisitus'' is in fact a junior synonym of ''Tsaagan mangas''. Xu, Pittman ''et al''. (2015) reject this synonymy by responding to the counterarguments proposed using new and existing details of ''Linheraptors anatomy. Below are the results for the Eudromaeosauria

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological s ...

based on the

phylogenetic analysis In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

performed by Currie and Evans in 2019:

Paleoenvironment

''Tsaagan'' represents the only dromaeosaurid remains (other than isolated teeth) known from the Ukhaa Tolgod region, though another dromaeosaurid, ''Velociraptor'', is known from the same

. Animals that may have shared the same habitat with ''Tsaagan'' include '' Protoceratops'', '' Shuvuuia'', the small

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

Zalambdalestes ''Zalambdalestes'' (meaning ''much-like-lambda robber'') was a eutherian mammal, most likely not a placental due to the presence of an epipubic bone, living during the Upper Cretaceous in Mongolia. ''Zalambdalestes'' was a hopping animal wi ...

'', the

multituberculate Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct order of rodent-like mammals with a fossil record spanning over 130 million years. They first appeared in the Middle Jurassic, a ...

mammal ''

Kryptobaatar ''Kryptobaatar''and also known as ''Gobibaatar'' or ''Tugrigbaatar'' is an extinct mammalian genus dating from the Upper Cretaceous Period and identified in Central Asia. This animal was a member of the extinct order of Multituberculata within ...

'', as well as several lizards and two yet-undescribed species of

troodontid Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil disco ...

and dromaeosaurid.

References

{{Taxonbar, from=Q133110 Late Cretaceous dinosaurs of Asia Djadochta fauna Eudromaeosaurs Fossil taxa described in 2006 Taxa named by Xu Xing Taxa named by Mark Norell Taxa named by James M. Clark

Discovery and naming

Description

Classification

Paleoenvironment

See also

References