page_title: Xingxiulong
section_title: Vertebrae
hierarchical_section_title: Xingxiulong / Description / Vertebrae
caption_attribution_description: English: Xingxiulong fossil sacral vertebrae and pubic bone
context_page_description: Xingxiulong is a genus of bipedal sauropodiform from the Early Jurassic of China. It contains a single species, X. chengi, described by Wang et al. in 2017 from three specimens, two adults and an immature individual, that collectively constitute a mostly complete skeleton. Adults of the genus measured 4–5 metres long and 1–1.5 metres tall. Phylogenetic analysis suggests that Xingxiulong is most closely related to its contemporary Jingshanosaurus, although an alternative position outside of both the Sauropodiformes and Massospondylidae is also plausible.
  Despite their close relationship, Xingxiulong prominently differs from Jingshanosaurus - and from most basal sauropodomorphs - in having a number of sauropod-like traits. These include a sacrum containing four vertebrae; a pubis with an exceptionally long top portion; and the femur, the first and fifth metatarsals on the foot, and the scapula being wide and robust. These probably represent adaptations to supporting high body weight, in particular a large gut. Unlike sauropods, however, Xingxiulong would still have been bipedal.
context_section_description: There are ten cervical vertebrae in the neck of Xingxiulong. The proatlas, an atrophied vertebra positioned in front of the atlas, is bounded in front by top sides of the foramen magnum. While it is difficult to say much about the atlas itself due to damage, the immediately following axis has a relatively short centrum, which is slightly compressed on its sides and bottom. Overall, the remainder of the cervical vertebrae are relatively short, being only 2.5 to 3 times as long as they are tall; they become increasingly shorter towards the back of the neck, like Lufengosaurus. Other basal sauropodomorphs, including Jingshanosaurus, have cervical vertebrae that are generally 3 to 4 times as long as they are tall. On the bottom of the centra of cervical vertebrae 4-9, there is a prominent keel as in Lufengosaurus, Jingshanosaurus, and other basal sauropodomorphs. Near the back of the neck, the neural spines become somewhat table-like.
  The fourteen dorsal vertebrae are weakly amphicoelous, or concave on both ends, typical of basal sauropodomorphs. Also typical is the presence of blade-like keels on the undersides of the first to third dorsal vertebrae, which are not seen elsewhere; additionally, the dorsal vertebrae near the front have the typical low, short, and somewhat plate-like neural spines. Unusually, however, the same kinds of neural spines are also seen in the last three dorsal vertebrae, which is only otherwise seen in basal saurischians like Herrerasaurus and Eoraptor. In the middle and back dorsal vertebrae, the top back corner of the neural spines project outward to produce a concave back edge, which is seen in some other basal sauropodomorphs but not Lufengosaurus, Jingshanosaurus, Yunnanosaurus, and Riojasaurus.
  Unusually among basal sauropodomorphs, Xingxiulong has four sacral vertebrae. This is a trait typically seen in more derived sauropodomorphs, like Melanorosaurus, Leonerasaurus, Barapasaurus, and Shunosaurus. The first of these sacral vertebrae, the dorsosacral, is not very well-fused to the next sacral vertebra; neither is it entirely fused to the corresponding sacral rib on the transverse processes. Collectively, the dorsosacral and first pair of sacral ribs extend forward to contact the ilium. The second and third sacral vertebrae, the two primordial sacrals, are about the same length, and are well-fused to each other. Like other basal sauropodomorphs, the transverse processes of the third sacral vertebra project backwards and outwards. The same is true of the transverse process and sacral ribs for the fourth sacral vertebra, which contact the ilium again at the back. All of the neural spines are plate-like, like the last few dorsal vertebrae.
  It is probable that Xingxiulong would have had more than the 35 preserved caudal vertebrae in the tail. These vertebrae are overall tall and very robust, and have concave sides like other basal sauropodomorphs. They also all appear to be amphicoelous. The transverse processes of the first several caudal vertebrae are wide and flat, and directed upwards and outwards; the transverse processes of caudal vertebrae further back in the tail are more slender and horizontal. As for the neural spines, they are tall and thin, and are directed somewhat backwards.
caption: Sacral vertebrae (a-d) and pubis (e-h) of Xingxiulong
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