Nanshiungosaurus brevispinus, Dong, Zhiming, 1979

Dong, Zhiming, 1979, Dinosaurs from the Cretaceous of South China, Mesozoic and Cenozoic Red Beds of South China: Selected Papers from the " Cretaceous-Tertiary Workshop ", Institute of Vertebrate Paleontology and Paleoanthropology & Nanjing Institute of Paleontology, Nanxiong, China: Science Press, pp. 342-350 : 2-5

Nanshiungosaurus brevispinus sp. nov.

(Plate II, Figure 1)

Diagnosis: A short neck with platycoelous anterior cervicals and opisthocoelous posterior cervicals, pleurocoels are undeveloped, neural spines are low, and the posterior series is not distinctly bifid. Cervical count is 12 and centra length is 2.5 times that of the dorsal centra. Dorsal count is 10 with platycoelous centra of equivalent height and length that have shallow pleurocoels. Neural spines are low and transversely broadened with a broad apex. Five well-fused sacral centra are present that have short unified neural spines with inflated apices and saddle-shaped depressions. The ilium is low with an extremely well-developed narrow and elongated preacetabular process, and the pubic peduncle is straight and robust. Pubis is linear with a thick lateral margin and closed obturator foramen. The ischium is thinly plate-shaped with expansive and fused distal ends. The acetabulum is large and circular.

Material: A string of articulated cervical, dorsal, and sacral vertebrae. Pelvic girdle is basically complete with the exception of the right ilium and pubis ( V4731 ).

Locality and stratigraphic position: Upper Cretaceous Nanxiong Fm. at the village of Dapingcun, Shuikou Commune (Loc. 74015).

Description: The vertebral count may be accurately determined as: cervicals 11, dorsals 10, and sacrals 5. A single caudal is articulated with the sacral series. The atlas has been lost, but the axis is complete, represented by a platycoelous centrum that is 13.5 cm in length, medially constricted, has a relatiively circular posterior end, and pleurocoels that are shallow and located anteriorly, dorsal to the parapophyses. The odontoid process is firmly fused to the anterior centrum and has a semicircular depression ventrally to facilitate the atlas centrum. The neural arch is relatively low, with circular facets that articulate with the atlantal postzygapophyses. The neural spine ascends posteriorly. The axis centrum morphology resembles that of Apatosaurus .

Posterior to the axis, the cervical vertebrae gradually increase in length, the longest being Cv7-8 with a centrum length of 18 cm. Posterior to this point the centra again reduce in length. The anterior cervicals are platycoelus with shallow pleurocoels, but there is also an additional small ridge or angle. The ventral centrum is flat, slightly medially constricted, and there are two longitudinal crests on the margins causing the centrum to be nearly rectangular. The thick but flattened anterior parapophyses extend ventrolaterally to fuse tightly with the capitulum on the ribs. The neural arches are low, the prezygapophyses extend anteriorly, and the anterior lobes of the diapophyses extend ventrally and also obliquely laterally to form a plate for articulation with the tuberculum. This morphology is frequently noted in the Sauropoda . The postzygapophyses are short, the neural spines are low and thin, and the most posterior centra are opisthocoelous, although the posterior sulcus is extremely shallow. The neural spines are transversely broadened and are not distinctly bifid.

Ten relatively well-preserved dorsal vertebrae are present, with the exception of the eighth through tenth which have damaged centra. The centra are short, platycoelous, 7 cm in length, and have shallow pleurocoels, but the several most posterior pleurocoels have been lost. The parapophyses have been lost, and replaced only by vestigial circular facets on the anterior centrum. The neural spines extend high, the pre- and postzygapophyses are within the bounds of the centrum, the neural spines are particularly low, transversely broadened, and thick; and the apices have a thick tuberosity. The morphology and configuration of all the processes conform to the general condition of the Sauropoda . A ventral keel is present that becomes more prominent posteriorly. The several most posterior dorsal vertebrae are platycoelous, approaching the sacral morphology. The centra (including the neural arch) are well pneumatized, such that in crosssection they are honeycombed and infilled with matrix, which is another generalized sauropod character.

Five solidly fused sacral vertebrae are present that are longer than the dorsals, ventrally inflated, and have low, transversely broadened neural spines with thick apices bearing a depression. All five neural spines are fused in into a single longitudinal plate.

There is only a single gently amphicoelous caudal preserved which lacks its neural spine. Its height and length are equivalent.

Of the pelvic girdle, the right ilium and pubis are lost, and although the remaining is completely preserved, compressional distortion has caused lateral curvature of the left ilium. The ilium is long and low with an extremely well-developed preacetabular process that resembles the condition of the Stegosauria. The pubic peduncle is well developed, being broad and straight. The pubis is linear with a thick lateral margin, and the ischial plate is relatively thin, expanded, and fused distally. The pubis and ischium are well fused, become compressed, and then extend posteriorly. The acetabulum is large and circular.

Comparison and discussion: The Nanxiong specimen is diagnosed as a member of the Sauropoda based upon the triradiate pelvic girdle, honeycombed internal structure of the vertebral centra, long cervical series with parapophyses ventrolaterally extended and strongly fused to the cervical ribs, and the neural spine height and foliate morphology. However, it also expresses some extremely autapomorphic characters, including the platycoelous centra, undeveloped pleurocoels, low and transversely expanded neural spines, and low ilium with an extremely well-developed preacetabular process. The undeveloped pleurocoel condition occurs in the subfamily Titanosaurinae , which is also characterized by rather short centra, low cervical neural spines that are bifid posteriorly, extremely small pleurocoels on the dorsal vertebrae, relatively broad and inflated dorsal neural spines, the presence of up to six sacral vertebrae, and a platycoelous first caudal. Forelimb-hind limb ratio is 3/4 and the limbs are straight and robust. This subfamily includes several Late Cretaceous genera that are rather rare and fragmentarily known in addition to being extremely autapomorphic, and consequently direct comparisons are difficult. Three genera are documented in Asia: Titanosaurus, Antarctosaurus , and Nemegtosaurus . The former two are from the Lameta beds of India and the latter from the Nemegt sediments of Mongolia, all of which are late Late Cretaceous.

The authors who erected the genus Nemegtosaurus state that a complete skeleton is at hand, but because the details are still unpublished, further comparisons cannot be made here.

The two Indian genera are also documented from General Roca, Argentina, but detailed descriptions are also not available at this time, and abstracts state that the specimens are extremely depauperate, consisting principally of vertebral centra and several limb bones. A single titanosaur centrum is also recorded from southern France.

The genus Titanosaurus is rather close to the Nanxiong specimens. The description of this Indian genus was conducted rather long ago upon restricted specimens and the descriptions are brief. Regardless, the posterior cervical neural spines are bifid, the first caudal is amphicoelous, and the Type is larger than the Nanxiong specimen. The two are so distinct that it is obvious the Nanxiong specimen belongs to a new clade. However, due to the current lack of cranial and diagnostic apendicular material, the Nanxiong specimens are provisionally recognized in the subfamily Titanosaurinae , and erected as Nanshiungosaurus brevispinus gen. et sp. nov.

Appended description. Within the collections made previously is a massive humerus which is typically sauropod in morphology. Young, (1965) described a pedicellate tooth that undoubtedly belongs to a sauropod, or the superfamily Homalosauropodidae, with a morphology approaching the teeth of Nemegtosaurus . Thus, it may be determined that the Nanxiong Fm. produces a sauropod that has phylogenetic relationships with the Indian Titanosaurus and Nemegtosaurus from Mongolia and the Xinjiang Autonomous region.