Yangchuanosaurus may be considered a sort of flagship animal for PNSO. Except for the ever-present Tyrannosaurus, it’s the dinosaur of which more versions have been made: the “Dayong the Yangchuanosaurus and Xiaobei the Chungkingosaurus” set in the Dinosaur Museum Series (you can read our review here), the Desktop Series faux bronze bust, a miniature in the “Seven Little Dinosaurs” set in partnership with the chinese postal service (this model was lately released as stand-alone, with a different paintjob) and last but not least the two figures featured in this review, “Dayong the Yangchuanosaurus shangyouensis” and “Dapeng the Yangchuanosaurus magnus”. Them being released barely one month apart each other is one of the reasons (not the only one) why we decided to cover them both in a single review.
The fossil – not complete, but well preserved – of Yangchuanosaurus shangyouensis (CV 00215) was unearthed in 1976 and described in 1978 by Dong, Zhang, Li and Zhou, while the more fragmentary remains of Yangchuanosaurus magnus (CV 00216) were discovered in 1973 but described only ten years after by Dong, Zhou and Zhang. The authors separated it from the type species on the basis of its size (Y.shangyouensis is 7 – 8 meters long, Y.magnus is more or less 10 meters long), of an additional fenestra inside the anteordbital fossa in Y.magnus while Y.shangyouensis has just a fossa and some other traits, but other researchers (Carrano et al, 2012) criticized this distinction saying that some of the traits (i.e. Y.shangyouensis having a foramen on the back of the mandible and Y.magnus having it not) may vary during the development (ontogeny) of theropods, among one specimen and the other and even between left and right side of the same specimen, or they might have been misinterpreted. Thus making Yangchuanosaurus magnus just a more mature specimen Yangchuanosaurus shangyouensis. Considering PNSO’s tendency at splitting (which is, separating species instead of lumping them) it’s no surprise they kept this distinction. It’s worth noting that there are no such visual differences between the two models to say that they belong to two different species. Instead, the paintjob and the crests and spikes are quite similar and they can be considered two specimens of the same species, one older and the other younger. PNSO did the ame thing with its Nanotyrannus in respect to Tyrannosaurus, while Torosaurus and Triceratops – that in PNSO’s opinion are two different genera – are cleary different in both colour and ornaments.
Dayong was noted, at its release, because it’s the first PNSO theropod in three years to feature extraoral tissues covering the teeth (the so-called “lips”, basically). Some of the first PNSO models in the Dinosaur Museum Series (Yangchuanosaurus and Giganotosaurus) had their teeth hidden when their mouth was closed. Since then, perhaps under the influece of Carr et al.‘s 2017 paper, all PNSO theropods featured a toothy smile, with Zhao Chuang explaining the reasons why in his videos. Then in march 2023 a paper by Cullen et al. brought evidence supporting theropods having the so-called lips. PNSO’s 2023 lineup till Dayong was all theropods, and all of them had exposed teeth, so everybody thought that PNSO wasn’t covinced of the lips evidencies. But Yangchuanosaurus, just like the Dinosaur Museum Series one, has labbra. PNSO giustified its choice saying that, when Yangchuanosaurus closes its mouth, the upper jaw is almost straight while the lower jaw curves upward (like a bowl), leaving a space between upper and lower teeth more akin to a lizard than other theropods. It sounds convincing, but why didn’t they do the same with last year “Sinraptor hepigensis“, being closely related animals with a close morphology?. Besides, PNSO’s next theropod is the Allosauroid Saurophaganax… whose skull there is very little of. No reasons, then, to model it differently than their 2020 Allosaurus if not a desire not to make their previous figures look surpassed. Perhaps not the most accuracy-friendly choice, but an understandable one.
The jaw articulation works well with lips: teeth are partially hidden by gums and when the mouth is closed there’s just a millimeter between upper and lower jaw. Probably a technical limitation which is far less noticeable in-hand than it’s in my photos. The skull of CV 00215 is almost complete; more difficult, as Zhao Chuang himself admits in a video, is to understand at what level it’s deformed, so PNSO decided to restore it 1:1 with the fossil. The skull of CV 00216, instead, was left exposed to the weather and the upper and posteriormost part is lost. It’s restored using CV 00215 as base, but with bigger lacrimal and nasal crests, supporting the idea that Dapeng is the fully mature form of Dayong. The crests coul’ve been even bigger, tho, since Dong et al., 1983 says how the rugosities of the bones indicate extensive keratinous ridges.
Looking at the side view of the two figures, we see the back lowering just before the hip (it’s less noticeable in Dapeng due to its upright pose). This is due to a progressive shortening of the dorsal vertebrae of more or less ten centimeters: not much, and other artists restore Yangchuanosaurus with a straighter profile, saying that it wouldn’t be noticeable once soft tissues are added. This feature is only hypothetical in Yangchuanosaurus magnus, since there are just six dorsal vertebrae preserved vs the more complete presacral (before the hip) skeleton of Yangchuanosaurus shangyouensis.
One of the differences between the two figures is the profile of the hip: in Dapeng, the hip area transitions to the tail without much change in height, while in Dayong there’s a sort of hump at the tail base. This because of the the different height of the neural spines of sacral and caudal vertabrae, which is higher (both in relative and absolute terms) in Yangchuanosaurus shangyuensis ( the spine of the fist caudal is 18 cm taller than the last sacral, while in Y. magnus it’s only 5 cm taller). Also contributing is the morphological difference between the ileum of CV 00215 and that of CV 00216, which was considered by Dong et al, 1983 a trait to separate the two species: in Yangchuanosaurus shangyouensis the ilium is lower, flatter and tapers towards the tail, while in Yangchuanosaurus magnus is taller, reaching the height of the sacrals and thus making the transition smoother.
There are only Metriacanthosauridae with a mostly complete forelimb, and those are ZDM 9011 and CV 00214. Funnily, they were both classified in the Szechuanosaurus genus (which is based on some teeth…), but Carrano et al (2012) found CV 00214 being another specimen of Yangchuanosaurus shanyouensis (smaller than both CV 00215 and CV 00216), while ZDM 9011 is from more ancient strata and it’s classified as another species of Yangchuanosaurus, Y.zigongensis. But other papers found it being far removed from Yangchuanosaurus, at the base of the Tetanurae tree (Dal Sasso et al. 2018). Dong et al. 1983 has some low quality photos of the forelimbs of CV 00214, but the hand claws are described as “extremely laterally compressed” e “large”, all of which is well represented in the PNSO figures. Y.zigongensis features a fourth metacarpal (an hand bone, in your palm there is one for each finger), a trait which disappeared in later tetanurans: it may have not represented in the PNSO figures due to the uncertainties about the placement of Y.zigongensis, or it might be encased in the hand flesh and thus not visible. A possible vestigial, reduced fourth metacarpal is als reported for Sinraptor dongi (Currie & Zhao, 1993).
The different pose of the two models makes harder to see it but, despite all the size advantage Dapeng has over Dayong, the femur of Yangchuanosaurus magnus it’s only 10 cm longer than that of Y.shangyuensis. The lower leg of CV 00216 is not preserved but – if the ratio between limb elements is the same as CV 00215 – then the proportions of Yangchuanosaurus weren’t the same when this animal grew: from a slender, small-headed and long-legged theropods it turned into a stockier, bulkier dinosaur with a bigger skull and shorter legs (something like that happens in other theropods, too, expecially in Tyrannosauridae). Or it might be further proof that Yangchuanosaurus shangyuensis and Y.magnus are two separate species. We wrote extensively about the reasons why Metriacanthosaurid tails are restored the way they are in the“Sinraptor” hepingensis review, so head there if you’re interested in the matter.
The two Yangchuanosaurus figures are a great addition to the the growing collection of Shangshaximiao dinosaurs by PNSO, catching the eye when exposed side by side, be them a younger and an older animal or two species of the same genus.
BIBLIOGRAPHY
Carr T.D.; Varricchio D.J.; Sedlmayr J.C.; Roberts E.M.; Moore J.R. (2017). A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system. Scientific Reports. 7: 44942
Carrano M. T.; Benson R. B.; Sampson S. D. (2012) The phylogeny of Tetanurae (Dinosauria: Theropoda). Journal of Systematic Palaeontology 10, 211–300
Cullen T.M.: Larson D.W.; Witton M.P.; Scott D.; Maho T.; Brink K.S.; Evans D.C.; Reisz R.; (2023) Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology. Science. 379(6639):1348-1352.
Currie P.J.; Zhao X.J, (1994) A new carnosaur (Dinosauria, Theropoda) from the Jurassic of Xinjiang, People’s Republic of China. Canadian Journal of Earth Sciences. 30(10), 2037-2081
Dal Sasso C.; Maganuco S.; Cau A. (2018). The oldest ceratosaurian (Dinosauria: Theropoda), from the Lower Jurassic of Italy, sheds light on the evolution of the three-fingered hand of birds. PeerJ. 1 (1): e5976
Dong Z.; Zhang Y.; Li X.; Zhou S. (1978) A new carnivorous dinosaur of Yongchuan, Sichuan. Chinese Science Bulletin 23, 302–304
Dong Z.; Zhou S.; Zhang Y. (1983). Dinosaurs from the Jurassic of Sichuan. Palaeontologica Sinica, New Series C 162(23): 1-136
Gao Y. (1992) Yangchuanosaurus hepingensis – a new species of carnosaur from Zigong, Sichuan. Vertebrata PalAsiatica. 30 (4): 313–324
Gao Y. (1993) A new species of Middle Jurassic Carnosauria from Dashanpu, Zigong, Sichaun Province, Szechuanosaurus zigongensis sp. nov. Vertebrata PalAsiatica 31(4):308-314
The author thanks Ivan Iofrida Paleoart and users from the Jagged Fang Designs KoFi Discord server for their help in writing this review.