| Qiaowanlong | |
|---|---|
 | |
| Restored skeleton | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Family: | †Euhelopodidae |
| Genus: | †Qiaowanlong You & Li, 2009 |
| Type species | |
| †Qiaowanlong kangxii You & Li, 2009 | |
Qiaowanlong (meaning "Qiaowan dragon") is anextinctgenus ofsauropoddinosaur.Fossils belonging to the genus were found in theYujinzi Basin of what is todayGansu Province,China.[1] The remains come from a geological formation called theXiagou Formation in theXinminpu Group, dating to the lateAptian Stage of theEarly Cretaceous.[2]
Theholotype ofQiaowanlong, given the designation FRDC GJ 07-14, was discovered in 2007 by a field expedition of the Fossil Research Development Center (FRDC), who were working on behalf of the provincial government ofGansu. One of the vertebrae of the specimen was broken during transport, but the specimen was excavated and moved to the Gansu Provincial Bureau of Geo-exploration and Mineral Development where they were prepared over the course of the next two years. The description was finally published in 2009 in theProceedings of the Royal Society B by the Chinese scientists Hai-Lu You and Da-Qing Li.[1]
The name of thegenus,Qiaowanlong is a reference to an important cultural site (Qiaowan) which is located near to where the fossils ofQiaowanlong were discovered. The name of the place itself is derived from theMandarin Chinese word"qiao" — which means "bridge" — and"wan" — which means "bend in a stream". The suffix of the genus name is"long", which means "dragon" and is a rough equivalent to theAncient Greek suffix,"saurus" (meaning "lizard"), and this is a common suffix in the naming conventions of dinosaurs and other reptiles found in China. Thespecies epithet,Q. kangxii, is in honor of theKangxi Emperor, who was said to have had dreams of the Qiaowan area.[1]
In their description ofQiaowanlong, You and Li remark that it is relatively small compared to some of its close relatives. They do not provide a full size estimate, but they do note that the seventh cervical vertebra (the longest of the known vertebrae) is 45 cm (18 in) in length. While large in absolute terms, this is only half the size of the same vertebra inGiraffatitan, and only about one-third of the size of the same vertebra inSauroposeidon. In spite of this relatively small size, the complete fusion of theneural arches to thecentra indicates that the holotype individual was a fully-grown adult when it died.[1] Later authors would publish estimates of the full size ofQiaowanlong.Gregory S. Paul suggested a length of about 12 m (39 ft) long and a weight of 6 tons[3] Rubén Molina-Pérez and Asier Larramendi suggested a much larger estimate of 20.7 m (68 ft) long, 4.3 m (14 ft) tall at the shoulder, and 13 tons in weight.[4]
Theholotype, and only specimen ofQiaowanlong consists of a series of eight vertebrae from the middle of the neck (probably C4-C11), the complete right half of the pelvis, and several bone fragments that the authors were not able to identify. From these remains, they were able to identify the followingautapomorphies, distinguishingQiaowanlong from all othersauropods: a relatively low elongation index of the vertebrae, deeply bifurcated neural spines, threefossae on the lateral sides of the cervical centra, a relatively shortenedischium, and a long pubic process of the ischium.[1]
When it was originally described,Qiaowanlong was believed to be member ofBrachiosauridae and to be a close relative ofSauroposeidon (which itself was also believed to be a brachiosaurid at the time).[1] Subsequent analyses have found a close relationship betweenQiaowanlong and the other AsiansauropodsEuhelopus andErketu, which would place it withinEuhelopodidae and therefore imply a closer affinity withtitanosaurs than with brachiosaurids.[5] Subsequent analyses have corroborated this finding. Below is an abbreviated cladogram recovered by Philip Mannion and colleagues.[6]
The Xiagou Formation is the second-youngest formation of the Xinminbu Group, and is stratigraphically positioned between the older Chinjinpu Formation and the younger Zhonggou Formation, all of which are located in the Yujingzi Basin of westernGansu. Today, this region is part of theGobi Desert, but during theEarly Cretaceous, it was a much less arid environment, and it was probably on or near the coast of theTethys Sea.[7]
The sediments of the formation consists of gray tomudstones andsiltstones interbedded withsandstones andconglomerates.[8] The composition of the Xiagou Formation indicates that there were likelylowlands surrounded by narrow hills, allowing dinosaurfaunas to travel across areas without geographical barriers. Some fossilized waterbirds have been preserved with the soft-tissues of theirwebbed feet and feathers still preserved, which has led authors to conclude that lakes withanoxic lake beds were also present.[7]
The fauna present in theXinminbao Group are hypothesized to be the ecological successors to the much more famousJehol biota, which existed inChina during theBarremian and the earlyAptian. This fauna, called the "Mazongshan fauna" by some authors, consists of mostlydinosaurs, because the rocks of theXiagou Formation mostly preserve large vertebrates.[9] There is a major exception to this trend, which are birds. There are numerous well-preserved bird fossils in the Mazongshan biota, most of which areenantiornithines, with relatively fewornithuromorphs. There are also some fish and arthropod fossils preserved in the region.[10][11]
The most numerous remains found in the region are non-avian dinosaurs. Of these, smallceratopsians were the most abundant, and account for the greatest number of fossils. There are also basalhadrosauroids,titanosauriformsauropods, and large herbivorousornithomimosaurs andtherizinosaurs. Other fragmentary remains have been attributed tooviraptorosaurs, but these have been called into question by some authors.[9]
Qiaowanlong is the only fossil so far known from the Qiaowan locality.[12] Other animals known from the Xiagou Formation, which may have directly coexisted withQiaowanlong, included theornithopods,Xuwulong andJintasaurus, thetyrannosauroid,Xiongguanlong, and the therizinosaur,Suzhousaurus. The smallneoceratopsianArchaeoceratops is also present in the area.[9] Enantiornithine birds were abundant and included genera such asAvimaia,Feitianius, and several unnamed forms, and they were accompanied by earlyeuornithean birds such as the duck-likeGansus and the unusual toothedBrevidentavis.[11] Several turtle skeletons have also been found.[9]
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