Xingxiulong (meaning "Xingxiu Bridge dragon") is a genus of bipedal massopodan sauropodomorph from the Early Jurassic of China.

A second species, X. yueorum, was described by Chen et al. in 2025 based on a partial articulated postcranial skeleton of an adult individual larger than X. chengi.

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.

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.

The rocks that these specimens were preserved in, consisting of purple silty mudstone, belong to the Early Jurassic Shawan Member of the Lufeng Formation, which has been tentatively dated to being Hettangian in age.

The generic name (literally meaning "constellation") refers to the Xingxiu Bridge (星宿), which was constructed during the Ming Dynasty of China.

Meanwhile, the specific name chengi honours Professor Zheng-Wu Cheng, who made major contributions to the biostratigraphy of China, including that of the Lufeng area, and died in 2015.

The specific name honors the siblings of Shu-Yong Yue for their work in collecting and preparing Lufeng dinosaur fossils, including the X.

The basipterygoid processes are long, slender, and project downwards and outwards like Plateosaurus and unlike Lufengosaurus and Jingshanosaurus, forming an angle of 80° with each other.

[1] Compared to Lufengosaurus, Yunnanosaurus, and Jingshanosaurus, the angular and surangular extend much further in front of the mandibular fenestra in Xingxiulong, which is closer to Adeopapposaurus and Plateosaurus.

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.

[1] The tuberosity on the inner surface of the top end of the humerus is rather poorly-developed in Xingxiulong, in contrast to the majority of basal sauropodomorphs (including Lufengosaurus and Yunnanosaurus).

The outer face of the pubic apron is somewhat concave, and the bottom end is expanded forwards and backwards to about 16% the length of the entire bone.

Viewed from the front, the trochanter is close to the midline of the bone, like other basal sauropodomorphs except for Antetonitrus and Melanorosaurus (in which it is closer to the outer edge).

Traits that are shared by Xingxiulong and Jingshanosaurus include the infratemporal fenestra being placed entirely behind the eye socket; the scapula being at least 20% as wide as it is long; the pubic apron, or the bottom of the pubis, having a concave outer face; the expansion at the bottom of the apron being at least 15% the length of the entire bone; and the angle between the femoral head and the cross-sectional axis of the femoral shaft being about 30°.

[1] Riojasaurus Eucnemesaurus Massospondylidae Yunnanosaurus Jingshanosaurus Xingxiulong Anchisaurus Mussaurus Aardonyx Melanorosaurus Lessemsaurus Antetonitrus Leonerasaurus Sauropoda Various alternative phylogenetic placements of Xingxiulong were tested; out of these, the most plausible alternative involves it being placed as a basal member of the Massopoda, outside of either Massospondylidae or Sauropodiformes, which only requires two additional evolutionary steps.

This is probably due to the curved top margin of the postorbital and the presence of a process behind the jaw joint on the articular, which are traits that, compared to either Massospondylidae or Sauropodiformes, can be regarded as relatively primitive.

These include the four-vertebra sacrum (which Mussaurus also convergently acquired);[7][12][17] the long pubic plate, or top portion of the pubis, which occupies 40% of the length of the bone (this figure is 25% in most other basal sauropodomorphs,[9] 33% in most sauropods,[18] and 45-50% in the Camarasauromorpha[19]); and the relative robustness of the femoral shaft,[12] first metatarsal,[20] top end of the fifth metatarsal, and scapula.

The large and robust scapulae of Xingxiulong, Jingshanosaurus, and Yunnanosaurus may have increased the mobility of the forelimb during bipedal browsing, but this trait was later adopted as an adaptation to quadrupedality in sauropods.

[21] Many sauropodomorphs aside from Xingxiulong are known from the Lufeng Formation, including Lufengosaurus huenei, L. magnus, Yunnanosaurus huangi, "Gyposaurus" sinensis, Jingshanosaurus xinwaensis, Chuxiongosaurus lufengensis,[1] Xixiposaurus suni, Yizhousaurus sunae,[22] and Pachysuchus imperfectus.

Also present are the theropods Sinosaurus triassicus, Lukousaurus yini,[21] Shidaisaurus jinae,[22][23] and Eshanosaurus deguchiianus;[24] the ornithischians Tatisaurus oehleri[21] and Bienosaurus lufengensis; the crocodylomorphs Dibothrosuchus elaphros, Platyognathus hsui, Microchampsa scutata, and Dianosuchus changchiawaensis, and Dianchungosaurus lufengensis; the indeterminate archosaur Strigosuchus licinus; the sphenodontians Clevosaurus petilus, C. wangi, and C. mcgilli; the tritylodontid cynodonts Bienotherium yunnanense, B. minor, B. magnum, Lufengia deltcata, Yunnanodon brevirostre, and Dianzhongia longirostrata; the mammals Sinoconodon rigneyi, Morganucodon oehleri, M. heikoupengensis, and Kunminia minima; proganochelyid turtles; and a "labyrinthodont" amphibian.