''Ruixinia'' is an extinct genus of somphospondylan

titanosauriform Macronaria is a clade of sauropod dinosaurs. Macronarians are named after the large diameter of the nasal opening of their skull, known as the external naris, which exceeded the size of the orbit, the skull opening where the eye is located (henc ...

dinosaur from the

Early Cretaceous The Early Cretaceous (geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pr ...

(

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma ( million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is pre ...

)

Yixian Formation The Yixian Formation (; formerly transcribed as Yihsien Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the late Barremian and early Aptian stages of the Early Cretaceous. It is known for its ...

of China. The genus contains a single species, ''Ruixinia zhangi''. The ''Ruixinia'' holotype is a partial articulated skeleton with the most complete series of caudal vertebrae known from any Asian titanosauriform.

Discovery and naming

The ''Ruixinia''

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, ELDM EL-J009, was found in sediments of the

Beipiao Beipiao () is a city in Chaoyang prefecture, Liaoning province, in Northeast China. It has a population of 202,807. The main industry in the area is coal mining. With vertical shafts of almost 1000m, these are some of the deepest coal mines in ...

Liaoning Province Liaoning () is a coastal province in Northeast China that is the smallest, southernmost, and most populous province in the region. With its capital at Shenyang, it is located on the northern shore of the Yellow Sea, and is the northernmost ...

, northeastern China. This locality is dated to the

age of the

period. The fossil material consists of a partial articulated skeleton including

cervical In anatomy, cervical is an adjective that has two meanings: # of or pertaining to any neck. # of or pertaining to the female cervix: i.e., the ''neck'' of the uterus. *Commonly used medical phrases involving the neck are **cervical collar **cervic ...

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal co ...

, and sacral vertebrae,

caudal vertebrae 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 ...

and associated chevrons, dorsal

ribs The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a semi ...

, and a left

ilium Ilium or Ileum may refer to: Places and jurisdictions * Ilion (Asia Minor), former name of Troy * Ilium (Epirus), an ancient city in Epirus, Greece * Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece * Ilium Building, a ...

, pubis,

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to te ...

metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the med ...

V, and possible pedal

phalanx The phalanx ( grc, φάλαγξ; plural phalanxes or phalanges, , ) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons. The term is particular ...

. At the time of its description, the fossil material was still partially embedded in

matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** '' The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...

, with only the left side of the bones prepared. In 2022, ''Ruixinia zhangi'' was described as a new genus and species of titanosauriform dinosaurs by Jinyou Mo, Feimin Ma, Yilun Yu, and Xing Xu. The binomial honors Ruixin Zhang, a contributor to the Erlianhaote Dinosaur Museum.

Description

''Ruixinia'' was a mid-sized sauropod, with an estimated length of approximately 12 meters. The neck of ''Ruixinia'' was over 4 meters long and consisted of at least 15 cervical vertebrae. Such a high number of cervical vertebrae is similar to '' Dongbeititan'', ''

Euhelopus ''Euhelopus'' is a genus of sauropod dinosaur that lived between 145 and 133 million years ago during the Berriasian and Valanginian stages of the Early Cretaceous in what is now Shandong Province in China. It was a large quadrupedal herbivore. ...

'', and ''

Mamenchisaurus ''Mamenchisaurus'' (or spelling pronunciation ) is a genus of sauropod dinosaur known for their remarkably long necks which made up nearly half the total body length. Numerous species have been assigned to the genus; however, many of these might ...

''. The tail of ''Ruixinia'' contained at least 52 vertebrae. The last few vertebrae were fused together, an unusual trait in sauropods otherwise only known to occur in some Jurassic Asian sauropods such as ''Shunosaurus'' and ''Mamenchisaurus''. However, the structure of the fused vertebrae differs between the three taxa. In ''Ruxinia'', the fused vertebrae form a rodlike structure. The chevrons are distinctive, particularly that of the 20th caudal vertebra, which has a pentagonal shape.

Classification

Mo ''et al''. (2022) recovered ''Ruxinia'' to be a basal

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still th ...

, placed as the sister taxon of a clade containing '' Daxiatitan'' and '' Xianshanosaurus''. However, both ''Daxiatitan'' and ''Xianshanosaurus'' have also been suggested to have affinities with mamenchisaurids, and Mo et al. noted several similarities between ''Ruixinia'' and ''Mamenchisaurus''. ''Ruixinia'' was not found to be closely related to either of its contemporaries, ''Dongbeititan'' or '' Liaoningotitan''. The

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

below displays the results of the phylogenetic analyses of Mo ''et al''. (2022).

Paleoecology

''Ruixinia'' is a member of the

Jehol Biota The Jehol Biota includes all the living organisms – the ecosystem – of northeastern China between 133 and 120 million years ago. This is the Lower Cretaceous ecosystem which left fossils in the Yixian Formation and Jiufotang Formation. These ...

. Two other sauropod genera, ''Dongbeititan'' and ''Liaoningotitan'', are also known from the Jehol Biota.

References

{{Portal bar, Dinosaurs, China Macronarians Barremian life Early Cretaceous dinosaurs of Asia Cretaceous China Fossil taxa described in 2022 Taxa named by Xu Xing