Spicomellus: extreme armor in a Middle Jurassic ankylosaur
Maidment et al 2025 reported,
“Spicomellus afer was suggested to be the world’s oldest ankylosaur and the first from Africa, but was based on only a single partial rib from the Middle Jurassic of Morrocco” (Madiment et al 2021.
‘Here we describe a new, much more complete specimen that confirms the ankylosaurian affinities of Spicomellus, and demonstrates that it has uniquely elaborate dermal armour unlike that of any other vertebrate, extant or extinct.”
Figure 1. Spicomellus restoration from publicity and video attending the publication.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/spicomellus588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/spicomellus588.jpg?w=584″ class=”size-full wp-image-94347″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/spicomellus588.jpg” alt=”Figure 1. Spicomellus restoration from publicity and video attending the publication.” width=”584″ height=”414″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/spicomellus588.jpg?w=584&h=414 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/spicomellus588.jpg?w=150&h=106 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/spicomellus588.jpg?w=300&h=213 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/spicomellus588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 1. Spicomellus restoration from publicity and video attending the publication.
This specimen is a topsy-turvy example of typical fossil preservation
in that very little of the skeleton is known. Instead, extradermal material is better preserved.
Figure 2. Scelidosaurus is from the Early Jurassic (190 mya) 30 million years prior to Spicomellus.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/08/jakapil-scelidosaurus2scale588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/08/jakapil-scelidosaurus2scale588.jpg?w=584″ class=”size-full wp-image-70876″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/08/jakapil-scelidosaurus2scale588.jpg” alt=”Figure 2. Scelidosaurus is from the Early Jurassic (190 mya) 30 million years prior to Spicomellus. ” width=”584″ height=”543″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/08/jakapil-scelidosaurus2scale588.jpg?w=584&h=543 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/08/jakapil-scelidosaurus2scale588.jpg?w=150&h=140 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/08/jakapil-scelidosaurus2scale588.jpg?w=300&h=279 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/08/jakapil-scelidosaurus2scale588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 2. Scelidosaurus is from the Early Jurassic (190 mya) 30 million years prior to Spicomellus.
Here
in the large reptile tree (LRT, 2336 taxa) Early Jurassic Scelidosaurus (Figs 2, 3) is the oldest tested ankylosaur and basal to that clade at 30 million years older than Spicomellus.
That makes sense in that extensive armor is a derived trait. One would expect ancestors to have less armor and less extreme armor.
The Wikipedia page on Spicomellus does not mention Scelidosaurus.
Maidment et al reported,
“Other compound osteoderms comprising two small spikes are known in the early-diverging thyreophorans Scelidosaurus and Yuxisaurus”.
In the LRT the traditional clade Thyreophora is not recovered. Yuxisaurus (Fig 3) lived in Early Jurassic China coeval with Scelidosaurus from England, where the authors live and work. So they had access.
Figure 3. Partly restored skull cast of Scelidosaurus to scale with the twice as large maxillary area of Yuxisaurus.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/scelidosaurus-skull-cast588.jpg?w=205″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/scelidosaurus-skull-cast588.jpg?w=584″ class=”size-full wp-image-94350″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/scelidosaurus-skull-cast588.jpg” alt=”Figure 3. Partly restored skull cast of Scelidosaurus to scale with the twice as large maxillary area of Yuxisaurus.” width=”584″ height=”854″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/scelidosaurus-skull-cast588.jpg?w=584&h=854 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/scelidosaurus-skull-cast588.jpg?w=103&h=150 103w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/scelidosaurus-skull-cast588.jpg?w=205&h=300 205w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/scelidosaurus-skull-cast588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 3. Partly restored skull cast of Scelidosaurus to scale with the twice as large maxillary area of Yuxisaurus.
According to Wikipedia – Yuxisaurus
“The holotype of the taxon, CVEB 21701, represents a partial skeleton including parts of the skull, several vertebrae, elements of the limbs, and at least 120 osteoderms.”
The Maidment et al cladogram
(their figure 3) did not include the taxon, Scelidosaurus, known from a nearly complete skeleton (Fig 2), but their cladogram did include the poorly preserved Yuxisaurus. Likewise, the authors did not include Minimi
This strikes me as odd. I hate to think their motivation for almost omitting Scelidosaurus was to create their own headline announcing ‘the world’s oldest ankylosaur’.
To alleviate any doubt, it would have been better to add Scelidosaurus (and perhaps Liaoningsaurus, Minmi and Emausaurus) to the published cladogram. Unfortunately, the LRT cannot yet handle Spicomellus because too few subdermal bones are known.
References
Maidment SCR et al (12 co-authors) 2025. Extreme armour in the world’s oldest ankylosaur. Nature (2025). https://doi.org/10.1038/s41586-025-09453-6
wiki/Spicomellus
wiki/Scelidosaurus
wiki/Yuxisaurus
Source: https://pterosaurheresies.wordpress.com/2025/09/01/spicomellus-extreme-armor-in-a-middle-jurassic-ankylosaur/
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