Size Xingxiulong was a medium- to large-sized
sauropodomorph. Adults of
X. chengi are estimated at long and tall at the hip. The two larger specimens, LFGT-D0002 and LFGT-D0003, are adults judging by the complete fusion in their skull; the third specimen, LFGT-D0001, is 14% smaller and probably represents a subadult judging by the incomplete fusion in the vertebrae. The holotype of
X. yueorum is larger than adult specimens of
X. chengi and is estimated to have been long in life; the longest femur of
X. chengi is about long, while the femur of
X. yueorum is long.
Xingxiulong does not have a ridge on the side of its
maxilla. Eleven tooth sockets are preserved along the length of the maxilla. Further back, in front of the eye socket, the
lacrimal bears a prominent projection near the top of its front end, which is also seen in
Lufengosaurus, and
Riojasaurus, but not
Yunnanosaurus,
Jingshanosaurus, or subsequent sauropodiforms. The contact surface between the
jugal bone and
postorbital bone is fairly long, like
Lufengosaurus but not
Yunnanosaurus. Among the three branches of the jugal, the backwards-directed branch forms an angle of 80° with the upwards-projecting branch, which is similar to
Plateosaurus and
Thecodontosaurus but much larger than other
sauropodomorphs. At the base of the skull, the
quadratojugal bears two branches, one pointing forwards and one upwards; they are roughly perpendicular to each other, unlike
Lufengosaurus (angle of 45°),
Yunnanosaurus (angle of 60°), and
Jingshanosaurus (angle of 110°). Above the quadratojugal, the
quadrate has two
articulating condyles, a subtriangular one facing outward and a more rounded one facing inwards; the latter condyle is placed closer to the bottom, like
Lufengosaurus and
Yunnanosaurus but not
Plateosaurus. At the back of the skull, between the
parietals and
supraoccipitals, there is a prominently developed postparietal fenestra; the supraoccipital itself slopes forwards at its bottom end so as to round off the base of the skull. 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. The articular bears an inward-projecting and pyramidal process as an extension of the jaw joint; at its back end, it also possesses an upward-directed and tab-like process, which is also seen in
Coloradisaurus,
Jingshanosaurus, and an as-of-yet unnamed sauropodomorph. 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.
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. and
Lessemsaurus have similarly robust scapulae, but the top end is more expanded in these two taxa. As with
Jingshanosaurus, the maximum width of the robust shaft of the scapula is 19-20% the length of the overall bone;
Antetonitrus although
Antetonitrus may have a similarly expanded metatarsal. Below the metatarsals, the five digits have a
phalangeal formula of 2-3-4-5-1. ==Classification==