''Qianxisaurus'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

pachypleurosaur Pachypleurosauria is an extinct clade of primitive sauropterygian reptiles from the Triassic period. Pachypleurosaurs vaguely resembled aquatic lizards, with elongate forms ranging in size from , with small heads, long necks, paddle-like limbs, a ...

or alternatively a basal

eosauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic diapsid reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosau ...

n known from the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

(

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...

age) of

Guizhou Province ) , image_skyline = , image_caption = , image_map = Guizhou in China (+all claims hatched).svg , mapsize = 275px , map_alt = Map showing the location of Guizhou Province , map_caption = Map s ...

, southwestern

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. It contains a single species, ''Qianxisaurus chajiangensis''.

Discovery

''Qianxisaurus'' is known solely from the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

NMNS-KIKO-F044630, a nearly complete and articulated

skeleton A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fra ...

missing only the tip of the tail and the right

hindlimb A hindlimb or back limb is one of the paired articulated appendages ( limbs) attached on the caudal ( posterior) end of a terrestrial tetrapod vertebrate's torso.http://www.merriam-webster.com/medical/hind%20limb, Merriam Webster Dictionary-H ...

, housed at the

National Museum of Natural Science The National Museum of Natural Science () is a national museum in North District, Taichung, Taiwan. Overview The museum covers and is a six-venue complex housing: the Space Theater, Science Center, Life Science Hall, Human Cultures Hall, Gl ...

Taichung Taichung (, Wade–Giles: '), officially Taichung City, is a special municipality (Taiwan), special municipality in central Taiwan. Taichung is Taiwan's second-largest city, with more than 2.85 million residents, making it the largest city in Ce ...

, Taiwan. The holotype is exposed mostly in a view from above, with the tail gradually turning to left side view. The skull measures at in length, and the total length of the individual is estimated to have been over . Only the first 31 tail vertebrae are preserved, out of at least 42-48 vertebrae that are expected to comprise the tail based on other closely related

s, which implies a total body length longer than 80 cm for this individual. NMNS-KIKO-F044630 was discovered in 2006 near the Huangnihe River at Chajiang of Xingyi, southwesternmost

. It was most probably collected from the Zhuganpo Member of the Falang Formation based on field expeditions to the area in 2006, somewhere between the Geju railway station and Chajiang railway station along the east side of the river which is the provincial boundary between Guizhou and Yunnan, thus dating to the

stage of the late

, about 238

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

Etymology

''Qianxisaurus'' was first described and named by Yen-Nien Cheng, Xiao-Chun Wu, Tamaki Sato and Hsi-Yin Shan in

2012 2012 was designated as: *International Year of Cooperatives *International Year of Sustainable Energy for All Events January *January 4 – The Cicada 3301 internet hunt begins. * January 12 – Peaceful protests begin in the R ...

and the

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

is ''Qianxisaurus chajiangensis''. The generic name is derived from ''Qianxi'', which refers to the western part of

where the holotype was found, a spelling based on the Chinese

Pinyin Hanyu Pinyin, or simply pinyin, officially the Chinese Phonetic Alphabet, is the most common romanization system for Standard Chinese. ''Hanyu'' () literally means 'Han Chinese, Han language'—that is, the Chinese language—while ''pinyin' ...

, and from

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''saûros'' (σαῦρος), Latinized as ''saurus'', meaning "lizard", a common suffix for genus names of extinct reptiles. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

is derived from ''Chajiang'', a town near which the specimen was collected, with the edition of the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

suffix ''-ensis'', meaning "from".

Description

''Qianxisaurus'' is a basal eosauropterygian, potentially related to Nothosauroidea, with an estimated total body length of at least . Originally considered to be a juvenile of the

nothosaurid Nothosauridae are an extinct family of carnivorous aquatic sauropterygian reptiles from the Triassic time period of China, France, Germany, Israel, Italy, Netherlands, Russia, Switzerland, and northern Africa. Phylogeny The cladogram shown bel ...

Lariosaurus ''Lariosaurus'' is an extinct genus of nothosaurid from the Middle Triassic (late Anisian to late Ladinian stage) of central and western Europe and China. With a complete specimen of ''L. xingyiensis'' measuring long and ''L. hongguoensis'' poss ...

'' due to the presence of four

sacral vertebrae The sacrum (: sacra or sacrums), in human anatomy, is a triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part of the pelvic cavity, ...

, further preparation revealed its unique

skull roof The skull roof or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes, including land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In com ...

and

dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiology ...

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

. ''Qianxisaurus'' bears a

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

with eight teeth, contributing a small portion to the elongated oval external

naris A nostril (or naris , : nares ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates, ...

, teeth with a slightly constricted peduncle and a short conical crown, and a very small supra

temporal fenestra Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly (al ...

, only slightly larger than the

foramen In anatomy and osteology, a foramen (; : foramina, or foramens ; ) is an opening or enclosed gap within the dense connective tissue (bones and deep fasciae) of extant and extinct amniote animals, typically to allow passage of nerves, artery, ...

of the

parietal bone The parietal bones ( ) are two bones in the skull which, when joined at a fibrous joint known as a cranial suture, form the sides and roof of the neurocranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four bord ...

. These autapomorphic traits are unique to ''Qianxisaurus'' among all known eosauropterygians. Other unusual traits include a snout longer than the rest of

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

, an irregular shape of

postorbital bone The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some ...

with a truncated projection of the top surface and a forked projection of the back surface, short and stout retroarticular process that is not concave but truncated in its back portion, a relatively long body with 28

back vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae of intermediate size between the cervical and lumbar ve ...

, the presence of four sacral vertebrae, ribs which are not pachyostotic, and a

coracoid A coracoid is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is present as part of the scapula, but this is n ...

with a narrow, column-shaped side portion and a widened, foot-shaped mid portion. ''Qianxisaurus'' shares the presence of a longitudinal groove on upper-back-facing surface of dorsal ribs exclusively with the potential basal

pistosauroid Pistosauroidea is a group of marine reptiles within the superorder Sauropterygia that first appeared in the latter part of the Early Triassic and were the ancestors of plesiosaurs. Pistosauroids are rare in Triassic marine assemblages, and are re ...

s ''

Corosaurus ''Corosaurus'' is an extinct genus of pistosauroid known from Wyoming of the United States. The holotype measured about long, while larger specimens would have belonged to individuals measuring more than long. History of discovery ''Corosauru ...

'', '' Sanchiaosaurus'', ''

Kwangsisaurus ''Kwangsisaurus'' is an extinct genus of a basal pistosauroid known from the Early or Middle Triassic (Olenekian or Anisian age) of Guangxi, southern China. It contains a single species, ''Kwangsisaurus orientalis''. Discovery ''Kwangsisaur ...

'' and ''

Chinchenia ''Chinchenia'' is an extinct genus of a basal pistosauroid known from the Middle Triassic (possibly Ladinian age) of Guizhou Province, southwestern China. It contains a single species, ''Chinchenia sungi''. Discovery ''Chinchenia'' is know ...

''.

References

{{Taxonbar, from=Q7267653 Fossil taxa described in 2012 Pachypleurosauria Triassic sauropterygians Middle Triassic reptiles of Asia Sauropterygian genera