Huashanosaurus, new eusauropod from Jurassic of China (free pdf)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper. (The pdf download is not working well for me right now, though)

Free pdf:

Huashanosaurus qini gen. et sp. nov.
 
MO Jinyou, ZHOU Xiuzhen, FU Qiongyao, XIONG Duo, HU Minhang & XU Xing (2025)
A New Eusauropod Dinosaur from the Lower and Middle Jurassic Wangmen Formation of Ningming County, Guangxi, South China
ACTA GEOLOGICA SINICA (English edition) 99(4): 909-924
DOI:10.1111/1755-6724.15331
https://www.geojournals.cn/dzxbcn/dzxbcn/article/abstract/2025endzxb04001

We report a new eusauropod dinosaur, Huashanosaurus qini gen. et sp. nov., based on a partial skeleton recovered from a bed in the Lower to Middle Jurassic Wangmen Formation (Fm.) from Huqiu Quarry near Mingjiang River, Ningming County, Guangxi Zhuang Autonomous Region, southern China. The new taxon can be diagnosed by the following autapomorphies: posterior process of the ulna hook-shaped; the cross-section of the proximal part of the ulna crescent-shaped; groove structure present at the posterodistal surface of the fibula. Phylogenetic analysis reveals that H. qini is later-diverging than the Middle Jurassic Shunosaurus. Previous work showed that the Wangmen Fm. is early Early Jurassic in age whereas the new eusauropod discovery indicates that the Wangmen Fm. is probably somewhat younger Early–Middle Jurassic in age. The find increases the diversity of Jurassic eusauropods in China.

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[Mickey Mortimer]

Yeah, it took me two tries to get the pdf to download fully. 

The specimen is REALLY fragmentary. When they say "one incomplete dorsal centrum", it's maybe two-thirds of the articular surface of 40% of a centrum, or "distal part of the left humerus" is just the mediodistal corner. The only complete elements are the "Possible right manual phalanx" and "possible right pedal phalanx", which aren't exactly the most diagnostic elements in sauropods. Based on their phylogenetic analysis it's Omeisaurus-grade, but their only noted differences from Omeisaurus are in the humeral fragment "In distal view, the medioposterior surface is round-shaped, ... rather than subtriangular present in Omeisaurus tianfuensis" and "The distal [actually proximal as stated in other places of the paper] end of the metatarsal V in Huashanosaurus qini is subtriangular in outline, different from ... Omeisaurus tianfuensis ... [where] the proximal ends of the metatarsals V are strongly expanded mediolaterally and compressed dorsoventrally." The round vs. subtriangular difference is also the only one noted for Omeisaurus-grade Anhuilong, then there's like nine other Omeisaurus species that are never mentioned. I'm no sauropod expert, but I can easily see this taxon being trashed the next time somebody reviews it.

That being said, the "dorsal surface of anteromedial process of ulna strongly concave, with distal end of anteromedial process level with olecranon; posterior process of ulna hook-shaped" is clearly different from O. tianfuensis T5704 (He et al., 1988: Fig. 46A), though who can tell the shaft's sectional shape in the latter from the paper. But O. tianfuensis T5701 DOES seem to have supposed Huashanosaurus autapomorphy "groove structure present at posterodistal surface of fibula" (He et al., 1988: Fig. 53C; note the left side has the groove because it is the opposite fibula than preserved in Huashanosaurus).

Omeisaurus luoquanensis can't be evaluated for any of Huashanosaurus' autapomorphies (no ulna or distal fibula), or the humeral and metatarsal V differences (no metatarsals or distal humerus). O. changshouensis doesn't have the fibular groove but can't be evaluated for anything else. In the type species O. junghsiensis only the fibula could possibly be compared but appears incomplete distally to me. O. puxiani lacks the hook-shaped posterior ulnar process and could probably be scored for its anteromedial process morphology if the overlying radius was removed. O. jiaoi is too briefly described to score for most of the autapomorphies, but does seem to have the fibular groove if I'm interpreting the lateral fibular edge correctly (Jiang et al., 2011: Fig. 6B). Interestingly, in O. maoianus the left humerus has Huashanosaurus' shape but the right one has O. tianfuensis' shape (Feng et al., 2001: Fig. 24D, 25D), suggesting substantial variation in this surface largely covered by cartilage in life, which makes me doubt its importance taxonomically. It lacks the anteromedial and posterior process shape characters of Huashanosaurus but the distal end of the anteromedial process is level with olecranon. Again the section at that point is not given. The fibular groove should be scorable, but both illustrations and plates only show it in lateral views which would not expose the groove. Metatarsals V are both preserved, 45% and 56% as broad as deep, compared to 74% in Huashanosaurus and 47% and 52% in Omeisaurus tianfuensis, so Huashanosaurus is indeed the outlier there. Omeisaurus fuxiensis cannot be compared at all (only cranial and cervical material). 

Finally, Anhuilong has Huashanosaurus' autapomorphy "dorsal surface of anteromedial process of ulna strongly concave, with distal end of anteromedial process level with olecranon", and the posterior process is even somewhat hook-like though not to the same degree (compare Ren et al., 2020: Fig. 3C). Ren et al. say of the ulna, "The ‘L’ shape of the proximal surface is transformed into an elliptical cross section at mid-shaft", suggesting a crescent-shape could be possible between those points, but don't tell us for certain. It doesn't preserve the hindlimb so can't be compared further to supposed autapomorphies, but "nearly perpendicular orientation of proximal end of ulna relative to long axis of ulnar shaft" is the one autapomorphy of Anhuilong that can be compared in Huashanosaurus, and they share it.

All of this certainly would have been interesting to read in Mo et al.'s paper. My provisional conclusion is the fibular groove is not an autapomorphy, being found in O. tianfuensis and possibly O. jiaoi, and that the ulnar characters are basically shared with Anhuilong, also from the Mid Jurassic of China and in the same phylogenetic position. It's not exactly the same shape, with Huashanosaurus' being more extreme, but I am a lumper. Maybe the deep proximal metatarsal V should be another autapomorphy, but I'm not sure what it's distribution is outside what I looked at here and apparently Mamenchisaurus hochuanensis (like Omeisaurus according to Mo et al.).

Mickey Mortimer