Anshunsaurus
Encyclopedia
Anshunsaurus is a genus
of thalattosaur
s within the family
Askeptosauridae
. Fossils have been found from Middle Triassic
deposits in Guizhou
, China
. Three species are known: the type species
A. huangguoshuensis (named in 1999), the slightly older species A. wushaensis (named in 2006), and the species A. huangnihensis (named in 2007).
bone in the skull, fused postorbital
and postfrontal bones around the eyes, a maxilla
that forms part of the margin of the eye socket
, a humerus
with large crests, and a large fibula. The type species of Ansunsaurus, A. huangguoshuensis, was named in 1999 from the Ladinian
or Carnian
age Falang Formation in Guanling County
. Although several complete skeletons are known, most specimens are crushed in either dorsal (top) or ventral (bottom) view. The holotype
of A. huangguoshuensis, IVPP 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 3.5 metres (11.5 ft) in length. Although the tip is not preserved in any specimen, the tail made up at least half of the animal's length.
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 spines 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. The pectoral and pelvic girdles are asymmetrical in this specimen, suggesting that the bones on the left and right sides of the animal did not ossify 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 bone of the pectoral girdle.
along with the genus Askeptosaurus
from Europe
. Both thalattosaurs belong to Askeptosauroidea
, 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.
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 thalattosaur
Thalattosaur
Thalattosaurs are a group of prehistoric marine reptiles which lived during the mid-late Triassic Period. Some species of thalattosaur grew to over 4 meters in length, including a long, flattened tail used in underwater propulsion...
s within the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Askeptosauridae
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.-Classification:...
. Fossils have been found from Middle Triassic
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. It spans the time between 245 ± 1.5 Ma and 228 ± 2 Ma...
deposits in Guizhou
Guizhou
' is a province of the People's Republic of China located in the southwestern part of the country. Its provincial capital city is Guiyang.- History :...
, 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...
. Three species are known: 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...
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 jugalJugal
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....
bone in the skull, fused postorbital
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 vertebrates, the postorbital is fused with the postfrontal...
and postfrontal bones around the eyes, a maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
that forms part of the margin of the eye socket
Orbit (anatomy)
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...
, a humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
with large crests, and a large fibula. The type species of Ansunsaurus, A. huangguoshuensis, was named in 1999 from the Ladinian
Ladinian
The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between 237 ± 2 Ma and 228 ± 2 Ma...
or Carnian
Carnian
The Carnian is the lowermost stage of the Upper Triassic series . It lasted from about 228.7 till 216.5 million years ago . The Carnian is preceded by the Ladinian and is followed by the Norian...
age Falang Formation in Guanling County
Guanling Buyei and Miao Autonomous County
Guanling Buyei and Miao Autonomous County is an autonomous county in Anshun Prefecture, Guizhou Province of China.Area: 1466 km2.Population: 334,900 in 2008.Postal Code: 561300.Telephone Area Code: 0853...
. Although several complete skeletons are known, most specimens are crushed in either dorsal (top) or ventral (bottom) view. 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...
of A. huangguoshuensis, IVPP 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 3.5 metres (11.5 ft) in length. Although the tip is not preserved in any specimen, the tail made up at least half of the animal's length.
A second species, A. wushaensis, was named in 2006 from Xingyi
Xingyi, Guizhou
Xingyi is a county level city in Guizhou in southern China. It has an area of 2911 square kilometers and a population of 740,700 as the end of 2003.-History:-External links:*...
. A. wushaensis is slightly smaller than A. huangguoshuensis and has a smaller head relative to its body length. It also has shorter neural spines 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
Ontogeny
Ontogeny is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan...
other than Xinpusaurus. The pectoral and pelvic girdles are asymmetrical in this specimen, suggesting that the bones on the left and right sides of the animal did not ossify 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 bone of the pectoral girdle.
Classification
When it was first described in 1999, Anshunsaurus was thought to be a sauropterygian. In 2000, Anshunsaurus was identified as a thalattosaur and has remained in this group ever since. It was placed in the family AskeptosauridaeAskeptosauridae
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.-Classification:...
along with the genus Askeptosaurus
Askeptosaurus
Askeptosaurus is an extinct genus of aquatic reptile related to the thalattosaurian group. Their remains have been found in Italy and Switzerland.Askeptosaurus was a very thin, elongated creature, that probably swam like an eel...
from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. Both thalattosaurs belong to Askeptosauroidea
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...
, 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.