Pachyrhinosaurus (PNSO, 2020)

Pachyrhinosaurus is a North American centrosaur ceratopsid that has received an impressive surge in popularity in recent years. As a rather obscure dinosaur to the public, he appeared in the Disney film Dinosaur (2000) and is the protagonist of Walking With Dinosaurs 3D (2013), as well as having appeared in documentaries such as March of the Dinosaurs (2011). It was even supposed to appear in Jurassic World: Fallen Kingdom, before being traded at the last minute with Sinoceratops. It is therefore no surprise that from 2000 onwards the models of Pachyrhinosaurus began to flock: Safari, Papo, Battat and Vivid Toys all have their own version of this genre, the Beast of the Mesozoic is on the way, and several of these sculptures they are excellent, so – in front of the PNSO offer – one might wonder if there was really a need for another Pachyrhinosaurus. The answer could be yes.

Pachyrhinosaurus is a genus established in 1950 by Sternberg, who established the P. canadensis species. For half a century this animal has been an oddity among the centrosaurinae due to the absence of a nasal horn – it has also been speculated that the bone bulge actually supported a keratin horn – but between the end of the last century and the early 2000s they started other similar ceratopsids have been described: first, in 1994, Achelousaurus horneri, then a second species of Pachyrhinosaurus in 2003: Pachyrhinosaurus lakustai. It is precisely from this second species that the PNSO model is inspired – as, among other things, all Papo, Safari, Battat, etcetera: it seems that, with the horn rising from the center of the bony collar, P. lakustai is destined to attract more attention. It is not the only difference with the other species of Pachyrhinosaurus (in 2012 a third one, P. perotorum, was described): the nasal lump has smaller dimensions and is clearly distinct from the supraorbital ones. These bone bulges are none other than the nasal and supraorbital horns of the other centrosaurins, which are still seen in the young Pachyrhinosaurus, but which during ontogenesis are transformed into thick and robust bone masses. In addition to the absence of horns, the genus Pachyrhinosaurus can be distinguished from the other centrosaurins by shorter cranial bones, which suggest greater power.

Why is the PNSO model special in the midst of the offering of other Pachyrhinosaurus lakustai? Mainly, because – instead of presenting a generalized reconstruction – it is partly based on a very specific example: TMP 86.55.258. Initially, many turned up their noses in front of this model, because it did not represent the “classic” aspect with which the nasal draft of P.lakustai is represented: instead of a swelling on the muzzle, the structure appears compressed and flattened. Yet this is precisely the aspect it has in TMP 86.55.258, which is – by the way – the holotype, that is the specimen to which the name “Pachyrhinosaurus lakustai” is anchored and to which the new fossils are compared if you want. refer them to this species.

Why is it written above that the model is only partially based on TMP 86.55.258? Because this specimen features a single horn in the center of the bony collar, while the three horns showing the PNSO (and, incidentally, the Safari, Battat, etc.) appear to be based on TMP 1988.55.187. We now come to the epioccipitals, that is the protrusions present along the collar of the ceratopsids and often real horns in the centrosaurins. A condition similar to that of the PNSO model, with P2 crossing, appears to be present in TMP 1989.55.1241. So we can say that this reconstruction combines the muzzle of TMP 86.55.258, the central part of the bone collar of TMP 1988.55.187 and the upper part of TMP 1989.55.1241. Another characteristic of P.lakustai is the so-called “rostral comb”, two or three hook-shaped structures located just above the rostral bone (which forms the beak). The PNSO model features three.

The quirks of Pachyrhinosaurus end there, because – otherwise – its anatomy is pretty standard for a centrosaur. This does not mean that the rendering of the PNSO model is less accurate in this: first of all you can admire how the beak and the horns are pointed: it is certainly not a safe toy for children. The nostrils are huge, just as they should have been: some paleontologists, not explaining their function, hypothesized that the ceratopsids had nasal sacs that they were able to inflate like a balloon. The sculptor has chosen a more conservative approach here and similar structures are absent. The auditory openings are in the correct position.

The neck of the Pachyrhinosaurus PNSO is stocky and robust, as wide as the head: the sculptor decided to emphasize the muscular masses that must have been necessary to move such a heavy skull. The body is equally massive and clearly a well-fed animal: no trace of Paul shrinkwrapping here. The tail is longer than that of animals such as Triceratops, and it is pleasing to see that the differences in proportions between the various clades of ceratopsids have been taken into account. The hand has five fingers, of which only three have claws, while there are only four on the foot. The number of fingers, as well as the shape of the extremities, is correct, with the forelimbs slightly flexed.

The body is covered with scales larger than those depicted on the head, more or less regularly interspersed with large circular shields. We do not possess any imprints of the skin of Pachyrhinosaurus, so the sculptor was inspired by other centrosaurines such as Centrosaurus, which instead preserve the integument.

Comparison with Pachyrhinosaurus lakustai Battat (2014)

If we compare the dimensions of the model’s skull with those of P. lakustai, it results in a drop of about 1:25. It is not unusual to read seven, eight meters long for Pachyrhinosaurus on the internet, but similar measurements are based on P. canadensis and specifically on the non-cataloged specimen called “Drumheller specimen”. P. lakustai and P. perotorum were both smaller.

Ultimately, the Pachyrhinosaurus PNSO is for anyone looking for a realistic model of this animal, with a great deal of attention to fossil remains and – why not? – also a captivating color, thanks to the red that highlights the nasal draft and which contrasts with the sienna of the body and the ice blue of the eyes.

Bibliography:

Currie P.J.; Langston W.; Tanke D.H. (2008) A new species of Pachyrhinosaurus (Dinosauria, Ceratopsidae) from the Upper Cretaceous of Alberta, Canada. (pp. 1-108) in: Currie, P.J.; Langston, W.; Tanke, D.H. (2008) A New Horned Dinosaur from an Upper Cretaceous Bone Bed in Alberta. NRC Research Press, Ottawa, Ontario, Canada. (144 pp)

blogs.scientificamerican.com/tetrapod-zoology/the-ridiculous-nasal-anatomy-of-giant-horned-dinosaurs/

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