DEINOCHEIRUS (PNSO, 2022)

For almost forty years, Deinocheirus remained an enigma. In 1965 a Russian expedition at Altan Ula III unearthed the forelimbs of a theropod, complete with a pectoral girdle. Two and a half meters long, they were the largest discovered up to that time. No other fossils were found, save from part of the vertebrae and ribs, but they were enough to earn the creature that owned them the name Deinocheirus mirificus (“extraordinary, terrible hand”) that Polish paleontologists Osmólska and Roniewicz gave it in 1970. Popular reconstructions often represented it as an oversized “carnosaur”, but its resemblance to Ornithomimosauria was immediately seen. For forty years, therefore, the most plausible reconstruction of Deinocheirus was a giant ornithomimosaur, often a bigger version of Gallimimus (also from the Nemegt Formation).

In 2014, after a long story including the pursuit of some of the illegally excavated fossils around the world, two new specimens were finally published (Lee et al. 2014). Together, they allow us to get a pretty clear idea of the appearance of Deinocheirus. And what a bizarre appearance it was! Far from being just an enlarged Gallimimus, Deinocheirus turned out to be a strange crossbreed between a theropod, a duck, and a camel.

With such an unusual shape for a theropod, Deinocheirus immediately rose to fame and those big forelimbs, which had caused so much wonder in paleontologists, appear almost normal, as can be seen in the PNSO model: clutched to its chest, in profile the claws look almost hidden, but turn around the model and you’ll realize that – apart from Therizinosauridae – Deinocheirus remains one of the theropods with the largest claws known. The hindlimb ones, on the other hand, do not have much of terrible, small and blunt as they are. The claws of Deinocheirus’ foot were really like that, more similar to those of hadrosaurs than to other theropods. Note how the hindlimb has only three fingers, opposed to the classical theropod’s four: it’s not a mistake but a common feature to ornithomimosaurs, probably an adaptation to speed – fast animals tend to simplify the distalmost elements of the limb – even if Deinocheirus has taken a completely different path.

The flat head of the PNSO Deinocheirus towers above most theropods of the same brand. Despite being more or less as long as Acrocanthosaurus, the long neck and hump on its back make it appear distinctly larger. The skull of Deinocheirus is unique among theropods: in addition to being low and elongated, towards the tip it widens to a spatula-shape – or, if you like, a “duckbill” vaguely akin to that of some hadrosaurs. This feature is not so evident in the PNSO model, probably because the sculptor decided to cover the bones with a keratinous covering (in simpler terms, a beak like that of modern birds) that sightly alters its shape. For the same reason, the model has a downwardly curved rostrum while in the fossil it’s straight: a similar morphology is also found in hadrosaurs and some exceptionally well-preserved fossils (such as a mummy exhibited at the Natural History Museum in Los Angeles Country) show the bony core of the beak covered by a downturned keratinous beak, so it’s possible that it was the same for Deinocheirus. Another trait of this animal is very evident, instead: its mandible is higher than the rest of the skull, almost a Tyrannosaurus jaw than an Ornithomimus one. Although not very evident, as they are not emphasized by the color, near to the point of the beak, on the upper side, we find the nostrils, in the same pplace in which they’re on the fossil. The beak opens at a wide angle – and this is congruent with some features of the skull – and on the palate there are the choanal openings we expect from PNSO. The eyes are appropriately small: the skull is one-meter-long, but the sclerotic ring (a structure also present in present-day birds and which serves to support the eye and which is preserved in Deinocheirus) is only 8.5 cm wide – in modern reptiles, it fills about 3/4 of the eyeball (Carpenter, 2016).

The whole skull is covered with a glossy varnish that PNSO uses for keratin, while some roughness under the eyes and along the jaw suggests the transition to naked skin. Naked skin – and not scales, for the first time in a PNSO theropod – is also present on the neck, except for a small area around the top of the neural spines, on the lower side of the body below the flank and mid-thigh, and on the inner side of the forelimbs. The plumage distribution, predominantly on the dorsal side of the model, is based on an exceptionally well-preserved fossil of Ornithomimus (van der Reest et al. 2015), which features a similar covering. This fossil is also source of the skin fold that connects the hind limb to the body. The skin is rendered with extreme care: the folds follow the movement of the animal, becoming denser near the joints and where the neck curves, and together with the feathers details make the Deinocheirus one of the better sculpted PNSOs.

The rest of the Deinocheirus body is covered by a thick plumage, which seems to be composed of filamentous feathers (not true feathers, then), similar to the ones of the PNSO Yutyrannus. The plumage slightly alters the contours of the animal, but not enough not to notice that the Deinocheirus becomes thinner at the neural spines and wider on the chest: the “hump” of a chameleon, rather than that of a camel. What is truly impressive about feathering is how the feathers are not straight like a scale mail, but fall according to their weight, a detail particularly evident on the sides of the neural spines. Earlier I wrote that the plumage does not reach the underside, but this is a simplification: to be exact, the model features a feather ring around the base of the neck, which extends in two parallel rows of feathers (separated in the center and sides by naked skin) up to the hip bones. Certainly an original stylistic choice, even if without a scientific basis.

On the forelimbs, the hair-like feathers turn into real feathers, large enough to distinguish the rachis like that of the wing feathers of modern birds (or mesozoic paravians). Two Ornithomimus specimens show signs on the forelimbs that have been explained as the insertions of quills (Zelenitsky et al. 2012). However, other authors think there is not enough evidence that they were really quills and that restoring ornithomimosaurs with secondary feathers is probably overly speculative.

True feathers are present, again, at the tip of the tail, where they form a fan. Deinocheirus features a fusion of the two distalmost tail vertebrae, a condition reminiscent of the pygostyle of other dinosaurs and birds and which in many forms supports a feather fan. Fused vertebrae, tho, are found in animals which hadn’t have such fans (e.g. Beipiaosaurus, Liao et al 2021) and they might be pathological. Vice versa, a tail fan does not require a pygostyle (e.g. Microraptor). Therefore it’s safer to say that these tail feathers are speculative, too, like there is no evidence for the scutes covering the backs of the hands.

The paint application is certainly among the most complex – if not THE most complex – among the PNSO PVC models: just have a look at how the slate gray of the tail stirpes fades into the blue of the fan stripes, or how the main color of the body turns into stripes on the tail. The eye color is akin to that of some modern ground birds and adds even more realism to the model. All this comes with a cost: such a complex painting is extremely delicate, more than that of other PNSO models, so caution is suggested while handling it, as is suggested the use of the provided stand to prevent it from falling.

To sum it all up, the PNSO Deinocheirus is certainly one of the most interesting models of the Chinese brand, and a highlight for any collection.

Bibliography:

Carpenter, K. (2016) Acrocanthosaurus inside and out. University of Oklahoma Press, 137 pp

Lee Y.N., Barsbold R., Currie P., Kobayashi Y., Lee H.J., Godefroit P., Escuillié F, Chinzorig T. (2014) Resolving the long-standing enigmas of a giant ornithomimosaur Deinocheirus mirificus. Nature 515, 257–260 https://doi.org/10.1038/nature13874

Liao C.C., Zanno L.E., Wang S., Xu X. (2021) Postcranial osteology of Beipiaosaurus inexpectus (Theropoda: Therizinosauria). PLoS One. 2021 Sep 30;16(9):e0257913. doi: 10.1371/journal.pone.0257913.

Osmolska H., Roniewicz E. (1970) Deinocheiridae, a new family of theropod dinosaurs. Palaeontologica Polonica. 21, 5-19.

van der Reest A.J., Wolfe A.P., Currie P.J. (2015) A densely feathered ornithomimid (Dinosauria: Theropoda) from the Upper Cretaceous Dinosaur Park Formation, Alberta, Canada Cretaceous Research 58: 108–117.

Zelenitsky D.K., Therrien F., Erickson G.M., DeBuhr C.L., Kobayashi Y., Eberth D.A., Hadfield F. (2012) Feathered Non-Avian Dinosaurs from North America Provide Insight into Wing Origins. Science 338(6106): 510-514.

Thanks to Discord users Randomdinos, Justin, and SpinoInWonderland for their help in writing this article.