Wuerhosaurus

Wuerhosaurus was a stegosaur dinosaur which lived in China during the early and middle Cretaceous Period. It was one of the last stegosaurs to have existed, as they had largely been replaced elsewhere in the world by the ankylosaurians by that time.

Wuerhosaurus is known from two partial skeletons belonging to two different species of that genus. Based upon their size, the animal is estimated to have reached somewhere between 15 to 25 feet long, making it almost as big or perhaps just as big as Stegosaurus. However, unlike Stegosaurus with its tall diamond-shaped plates, Wuerhosaurus‘ plates were short and stumpy.

There are two species of Wuerhsaurus which are currently recognized by science: W. homheni (1973) and W. ordosensis (1993). The fossils of Wuerhosaurus homheni were found near Wuerho, Xinjiang Province, China within the rocks of the Lianmuqin Formation, which dates from 140 to 115 million years ago. The specific rock layer that the fossils of W. homheni were found in date to 130 MYA during the earliest part of the Hauterivian Stage of the early Cretaceous Period.

The fossils of Wuerhosaurus ordosensis were found in 1988 within the Ordos Basis, which lies within the “Inner Mongolia Autonomous Region” in northern China. The rocks there are from the Ejinhoro Formation and date to the boundary between the Aptian and Albian Stages of the middle Cretaceous Period, about 113 million years ago. The animal was named in 1993. Wuerhosaurus ordosensis is believed to have been slightly smaller compared to W. homheni.

A third species of Wuerhosaurus was named in 2014, called Wuerhosaurus mongoliensis. However, on further examination, it was determined that it was an entirely new genus, and so it was renamed Mongolostegus exspectabilis in 2018.

Although two partial skeletons have been found, there is still a lot that we don’t know about Wuerhosaurus‘ appearance. No skull was found with either specimen, and we don’t know how many back plates or tail spikes it would have had. Phylogeny suggests that it was an advanced stegosaur closely related to Stegosaurus itself, so it probably had a very similar appearance. This means that it likely had four tail spikes, no shoulder spikes as is seen in creatures like Kentrosaurus and Lexovisaurus, and it might have had pebbly dermal armor protecting the underside of its throat. One can only hope that more skeletons are found in the future.

In 2008, Susannah Maidment and her colleagues stated that Wuerhosaurus and Stegosaurus were so closely related that Wuerhosaurus should really be re-classified as a Chinese species of Stegosaurus. However, nobody seems to have taken any notice of that and practically everybody still refers to it as Wuerhosaurus (1).

There has also been a certain degree of talk concerning Wuerhosaurus‘ back plates. A total of three dorsal plates are known from Wuerhosaurus: two from W. homheni and one from W. ordosensis. The two plates from W. homheni are grouped together with the rest of the skeleton under the collection ID code “IVPP V4006”. The dorsal plate from W. ordosensis has been designated with the collection ID code “IVPP V6878” (2).

Susannah Maidment claimed that the short rectangular plates which Wuerhosaurus is depicted as having are actually a mistake. Her article claims that the plates were broken off horizontally, giving the illusion that they had a different shape, when in actuality they were probably very Stegosaurus-esque in their appearance (3). In 2010, the British paleontologist David Hone examined one of the two dorsal plates from “IVPP V4006”, and he also remarked that the dorsal edge of the plate looked broken rather than having a natural edge (4). Yet, remember that three plates were found belonging to two skeletons, and I find it hard to believe that all three plates could be broken in the exact same way – that would be a truly remarkable coincidence. Not impossible, but indeed very unlikely.

Below is a drawing which I made of the species Wuerhosaurus homheni, made with No.2 and No.3 pencil. The drawing measures 12 inches long from nose to tail, not including the tail spikes, which would make the drawing 1/20 scale if the creature measured 20 feet long, as I suspect it did. NOTE: I wasn’t satisfied with the original drawing which was posted here in late July, so I replaced it with the drawing that you see below.

Wuerhosaurus homheni. © Jason R. Abdale (August 11, 2022).

Keep your pencils sharp, people.

Source citations:

  1. Maidment, Susannah C.R.; Norman, David B.; Barrett, Paul M.; Upchurch, Paul (2008). “Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia)”. Journal of Systematic Palaeontology, volume 6, issue 4 (November 24, 2008). Pages 368, 379-380, 384.
  2. Maidment, Susannah C.R.; Norman, David B.; Barrett, Paul M.; Upchurch, Paul (2008). “Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia)”. Journal of Systematic Palaeontology, volume 6, issue 4 (November 24, 2008). Pages 379-380, 384.
  3. Comment #47, in Science Blogs. “Stegosaur Wars: the SJG stegosaur special, part I”, by tetrapodzoology (December 29, 2010). https://scienceblogs.com/tetrapodzoology/2010/12/29/stegosaur-wars. Accessed on July 29, 2022.
  4. Archosaur Musings. “Not Wuerhosaurus homheni”, by David Hone (January 5, 2010). https://archosaurmusings.wordpress.com/2010/01/05/not-wuerhosaurus-homheni/. Accessed on July 29, 2022

Bibliography

Maidment, Susannah C.R.; Norman, David B.; Barrett, Paul M.; Upchurch, Paul (2008). “Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia)”. Journal of Systematic Palaeontology, volume 6, issue 4 (November 24, 2008). Pages 367-407.
https://www.researchgate.net/publication/230854863_Systematics_and_phylogeny_of_Stegosauria_Dinosauria_Ornithischia.

Archosaur Musings. “Not Wuerhosaurus homheni”, by David Hone (January 5, 2010). https://archosaurmusings.wordpress.com/2010/01/05/not-wuerhosaurus-homheni/. Accessed on July 29, 2022.

Science Blogs. “Stegosaur Wars: the SJG stegosaur special, part I”, by tetrapodzoology (December 29, 2010). https://scienceblogs.com/tetrapodzoology/2010/12/29/stegosaur-wars. Accessed on July 29, 2022.



Categories: Paleontology, Uncategorized

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1 reply

  1. A most excellent post on Wuerhosaurus. It’s a classic example of “we need more fossils” to help settle the debate on the plates, but I think you make a fair point for why the unusual shape could be how they appeared.

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