| Gongxianosaurus | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Genus: | †Gongxianosaurus |
| Species: | †G. shibeiensis |
| Binomial name | |
| †Gongxianosaurus shibeiensis Heet al., 1998 | |
| Synonyms | |
| |
Gongxianosaurus is a genus of basalsauropoddinosaur from the earlyJurassic Period (Sinemurian-Pliensbachianstage[1]). The only species isGongxianosaurus shibeiensis. Based on four fragmentary to complete specimens found in theZiliujing Formation,China (Sichuan Province), it is one of the most completely known early sauropods. The skeleton is known in large part, missing both the hand and the majority of the skull.[2]Gongxianosaurus was firstly named and described in a short note published in 1998;[3] however, a comprehensive description has yet to be published.[4]Gongxianosaurus shibeiensis was named for the place it was found, near the village Shibei inGong County (珙县;Pinyin: Gǒng Xiàn).[2]
Gongxianosaurus may have reached 14 metres (46 ft) in length.[2] Like other sauropods, it movedquadrupedally (on four legs), as indicated by the elongated fore limbs that reached 70 to 75% of hind limb length.[2] Thepedal phalanges were short and robust, as typical for sauropods. The pedalphalangeal formula, counting the number of phalanges for each digit starting from the innermost, was 2-3-4-5-1. All but the outermost digit ended in claws.[2] Unlike in other sauropods,pleurocoels (deep lateral excavations of the vertebrae) were absent;[2] thus, the vertebrae would have been quite massive. Thesacrum was made of three fused sacral vertebrae, fewer than in later sauropods.[2][5] Thechevrons were unbifurcated.[2]
An important characteristic of sauropod limbs is their reducedossification – the tendency to replace bone bycartilage.Gongxianosaurus is the only known sauropod with ossified distaltarsals. Thus, eitherGongxianosaurus was one of the basalmost sauropods, or ossified distal tarsals were present in other early sauropods but are simply not preserved due to the fragmentation of the specimens.[5]
Because the fossils are not fully described yet, available character information that can be used incladistic analyses is limited. Thus, only few cladistical analyses have incorporatedGongxianosaurus. A recent analysis by Apaldetti et al. (2011) suggests thatGongxianosaurus was more basal thanVulcanodon,Tazoudasaurus andIsanosaurus, but more derived than the early sauropodsAntetonitrus,Lessemsaurus,Blikanasaurus,Camelotia andMelanorosaurus.[6]
Gongxianosaurus fossils were found near the village of Shibei (Sichuan province) in purplemudstones pertaining to theZiliujing Formation (Dongyuemiao Member).[3] These rocks were considered to beToarcian in age (182.7 to 174.1mya), but then the Sinemurian-Pliensbachian boundary event (192.9 Ma) was recorded on the top, while lower parts of this member are of Earliest Sinemurian age (around 199 Ma).[1][7] Thus,Gongxianosaurus, unlike it was previously thought, is geologically coeval with the "prosauropod"Lufengosaurus but older than the basal sauropodShunosaurus.[3]
Basal Sauropod phylogeny simplified after Apaldetti et al. (2011).[6] |
The fossils were found in May 1997 during a geological exploration. Excavation started in the same month and led to the recovery of a wealth of fossils in an area of approximately 200 square meters. While most fossils pertain to a new sauropod genus, remains oftheropods have also been found.[3] The sauropod material includes four fragmentary to complete individuals similar in size, together encompassing most of the skeleton, though hand and skull bones were not found except apremaxilla and teeth. In 1998, the sauropod material was briefly described as a new genus and species,Gongxianosaurus shibeiensis, in a preliminary note by palaeontologists led byHe Xinlu.[3] A more detailed description was announced, noting that excavation was still in progress while the paper was published.[3] In 2000, a second short description was published by Luo Yaonan and Wang Changsheng, also presentingGongxianosaurus as a new sauropod and without mentioning the first description that was published two years before.[2][8] Also, much of the information published by Luo and Wang was already published by He and colleagues.[8]
Luo and Wang suggest that several bones may not pertain to thetype speciesGongxianosaurus shibeiensis but to a second species ofGongxianosaurus.[2] Those remains were informally placed within the separate genus and species "Yibinosaurus zhoui" in 2001 and 2003 respectively byOuyang Hui.[9][10]
The holotype ofGongxianosaurus was keptin situ and a protective exhibition hall was built over it. The exhibition hall subsequently collapsed, and the specimen was most likely destroyed.[11]
