''Anshunsaurus'' 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 ...

thalattosaur Thalattosauria (Greek for "sea lizards") is an extinct order of prehistoric marine reptiles that lived in the middle to late Triassic period. Thalattosaurs were diverse in size and shape, and are divided into two superfamilies: Askeptosauroidea a ...

s within the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Askeptosauridae Askeptosauridae is a family of thalattosaurs within the superfamily Askeptosauroidea. Fossils have been found from Italy, Switzerland, and China. Askeptosaurids are distinguished from other thalattosaurs by their long necks and narrow skulls. ...

. Fossils have been found from

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...

deposits in

Guizhou Guizhou (; formerly Kweichow) is a landlocked province in the southwest region of the People's Republic of China. Its capital and largest city is Guiyang, in the center of the province. Guizhou borders the autonomous region of Guangxi to t ...

, China. Three species are known: the

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 specimen ...

''A. huangguoshuensis'' (named in 1999), the slightly older species ''A. wushaensis'' (named in 2006), and the species ''A. huangnihensis'' (named in 2007).

Description and species

''Anshunsaurus'' was a marine reptile with a long neck, slender skull, and long, paddle-like tail. In comparison to its long trunk, the limbs are very small. ''Anshunsaurus'' is characterized by a long

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 ...

bone in the skull, fused

postorbital 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 ve ...

and

postfrontal The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

bones around the eyes, 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 ...

that forms part of the margin of the

eye socket In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is , of ...

, a

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

with large crests, and a large

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...

. The type species of ''Anshunsaurus'', ''A. huangguoshuensis'', was named in 1999 from the

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). ...

Carnian The Carnian (less commonly, Karnian) is the lowermost stage of the Upper Triassic Series (or earliest age of the Late Triassic Epoch). It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by t ...

age

Falang Formation Farang ( fa, فرنگ) is a Persian (and Southeast Asian) word that originally referred to the Franks (the major Germanic tribe) and later came to refer to White Europeans in general. The word "Farang" is a cognate and originates from Old F ...

Guanling County Guanling Buyei and Miao Autonomous County (; Bouyei: ) is an autonomous county in Anshun City, in the southwest of Guizhou Province, China. Area: Population: 334,900 in 2008. Postal Code: 561300. Telephone Area Code: 0853 The county governme ...

. Although several complete skeletons are known, most specimens are crushed in either dorsal (top) or ventral (bottom) view. 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 several ...

of ''A. huangguoshuensis'',

IVPP The Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; ) of China is a research institution and collections repository for fossils, including many dinosaur and pterosaur specimens (many from the Yixian Formation). As its name suggest ...

V11835, is preserved in dorsal view while a second specimen, IVPP V11834, is preserved in ventral view. Based on these specimens, ''A. huangguoshuensis'' grew to about in length. Although the tip is not preserved in any specimen, the tail made up at least half of the animal's length. A juvenile specimen of ''A. huangguoshuensis'' was described in 2015. A second species, ''A. wushaensis'', was named in 2006 from Xingyi. ''A. wushaensis'' is slightly smaller than ''A. huangguoshuensis'' and has a smaller head relative to its body length. It also has shorter

neural spine The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

s with ridges on their upper surface, a shorter fourth digit on the hand, a well-developed entepicondyle on the humerus, and a shorter jugal bone. A juvenile specimen of ''A. wushaensis'' was described in 2007, making ''Anshunsaurus'' the only thalattosaur with a known growth series other than ''

Xinpusaurus ''Xinpusaurus'' is an extinct genus of thalattosaur from the Late Triassic of Guanling in Guizhou, China. Several species have been named since 2000: the type species ''X. suni'' along with the species ''X. bamaolinensis'' and ''X. kohi''. A 201 ...

''. The

pectoral Pectoral may refer to: * The chest region and anything relating to it. * Pectoral cross, a cross worn on the chest * a decorative, usually jeweled version of a gorget * Pectoral (Ancient Egypt), a type of jewelry worn in ancient Egypt * Pectoralis ...

and

pelvic girdle The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The p ...

s are asymmetrical in this specimen, suggesting that the bones on the left and right sides of the animal did not

ossify Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in th ...

at the same rate while it was growing. In 2007 a third species of ''Anshunsaurus'', ''A. huangnihensis'', was described from Xingyi. It is distinguished from the other two species on the basis of the shape of its

coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) 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 prese ...

, a bone of the pectoral girdle.

Classification

When it was first described in 1999, ''Anshunsaurus'' was thought to be a

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

. In 2000, ''Anshunsaurus'' was reidentified as a thalattosaur and has remained in this group ever since. It was placed in the family

along with the genus ''

Askeptosaurus ''Askeptosaurus'' is an extinct genus of askeptosauroid, a marine reptile from the extinct order Thalattosauria. ''Askeptosaurus'' is known from several well-preserved fossils found in Middle Triassic marine strata in what is now Italy and ...

'' from

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

. Both thalattosaurs belong to

Askeptosauroidea Askeptosauroidea is a superfamily of thalattosaurs, a Triassic group of marine reptiles. Askeptosauroidea is one of two major subgroups of Thalattosauria, the other being Thalattosauroidea. It includes the family Askeptosauridae and a more basal ...

, a group characterized by their long necks and narrow skulls. Of the three species of ''Anshunsaurus'', ''A. huangnihensis'' shares more features with other thalattosaurs such as ''Askeptosaurus'' and ''Endennasaurus''. These features suggest that ''A. huangnihensis'' is a transitional form between earlier thalattosaurs and the later species of ''Anshunsaurus''.

References

{{Taxonbar, from=Q3618359 Triassic diapsids Middle Triassic reptiles of Asia Prehistoric reptile genera