New Spicomellus fossils from Middle Jurassic of Morocco reveal bizarre oldest ankylosaur

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper:

Susannah C. R. Maidment, Driss Ouarhache, Kawtar Ech-charay, Ahmed Oussou, Khadija Boumir, Abdessalam El Khanchoufi, Alison Park, Luke E. Meade, D. Cary Woodruff, Simon Wills, Mike Smith, Paul M. Barrett & Richard J. Butler (2025)
Extreme armour in the world’s oldest ankylosaur
Nature (advance online publication)
doi: https://doi.org/10.1038/s41586-025-09453-6
https://www.nature.com/articles/s41586-025-09453-6


The armoured ankylosaurian dinosaurs are best known from Late Cretaceous Northern Hemisphere ecosystems, but their early evolution in the Early–Middle Jurassic is shrouded in mystery due to a poor fossil record. 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 Morocco. 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. The presence of ‘handle’ vertebrae in the tail of Spicomellus indicates that it possessed a tail weapon, overturning current understanding of tail club evolution in ankylosaurs, as these structures were previously thought to have evolved only in the Early Cretaceous. This ornate armour may have functioned for display as well as defence, and a later reduction to simpler armour with less extravagant osteoderms in Late Cretaceous taxa might indicate a shift towards a primarily defensive function, perhaps in response to increased predation pressures or a switch to combative courtship displays.

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A spiky armoured dinosaur from Africa causes a rethink of ankylosaur evolution
The body of Spicomellus, an armoured dinosaur (ankylosaur) from Morocco, was covered in extravagant spines, including spikes measuring nearly one metre in length that extended from a bony collar around the dinosaur’s neck. This elaborate armour might have been used for display, challenging the current theory of why ankylosaurs evolved their extensive body armour.

https://www.nature.com/articles/d41586-025-02690-9

*****

News:

“Bizarre” armoured dinosaur Spicomellus afer rewrites ankylosaur evolution

https://www.nhm.ac.uk/discover/news/2025/august/bizarre-armoured-dinosaur-spicomellus-afer-rewrites-ankylosaur-evolution.html

With video

https://www.birmingham.ac.uk/news/2025/bizarre-armoured-dinosaur-spicomellus-afer-had-spikes-sticking-out-from-its-neck-fossils-show

*****
https://phys.org/news/2025-08-bizarre-armored-dinosaur-spicomellus-afer.html

https://www.newscientist.com/article/2494030-armoured-dinosaurs-crazy-spikes-werent-just-for-defence/

https://www.sciencealert.com/this-incredible-dinosaur-sported-the-spikiest-armor-the-world-has-ever-seen

[Ben Creisler]

Note that Susie Maidment's Tweetisaurus on Bluesky has posted a read-only link. You can find it in the recent posts.

https://bsky.app/profile/tweetisaurus.bsky.social

On a personal note, I was contacted for help on naming the original fossil--a single rib with projecting spikes.  It reminded the authors of the collar on the bulldog Spike in old Tom and Jerry cartoons, who had a spiky collar in the earlier cartoons (with the points made blunt in later more "kid-friendly" episodes). I suggested a combination of Latin spica "spike" and mellum "dog collar (studded with nails)" (used in wolf hunting). They went with the spelling Spicomellus "spiky collar"--which turns out to be way more appropriate than originally imagined! The critter has huge spikes in a collar around its neck!

[Ben Creisler]

An additional video:

Spicomellus: 

New dinosaur is unlike anything we've ever found | Unique armoured dinosaur discovered in Morocco
Natural History Museum
9 min.

https://www.youtube.com/watch?v=TEeCFl0MJ0A

On Wed, Aug 27, 2025 at 10:09 AM Ben Creisler <bcre...@gmail.com> wrote:

[Gregory Paul]

Is there information anywhere on the level of the Morrison (lower, middle, upper) that the Cactus Park quarry is at? 

GSPaul

[Gunnar Bivens]

Foster (2003) reports it as being from Zone 4, so middle Morrison (it's similar in age to Dry Mesa Dinosaur Quarry).

https://drive.google.com/open?id=1d5efYKwgJiWM_K65iuW-Qtzz1WhIKJsa&usp=drive_fs

On Wed, Aug 27, 2025 at 5:42 PM 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

Is there information anywhere on the level of the Morrison (lower, middle, upper) that the Cactus Park quarry is at? 

GSPaul

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[Russell Engelman]

Wow, it looks like this is is that specimen that guy reported on Reddit a couple of years ago and forwarded to the authorities.

It would be nice if they had an actual skeletal in the paper rather than a life reconstruction. Reading it over it is very hard to visualize how much of the life reconstruction is based on found material and how much is interpolated.

Also, mark my words. Some company is going to make a toy of this thing in the next 5-10 years. Toy companies seem to love freaky new visually arresting dinosaurs (and dinosaur accessories) they can make models of. Looking at you, Bajadasaurus, Concavenator, Stegouros, and Lisowicia.

[Mickey Mortimer]

Very cool taxon. When Spicomellus was first described based on the holotype rib I was skeptical it was actually an ankylosaur because the spines fusing to the ribs in succession like that is so weird, but we have a partial skeleton here and yes it is.

In any case Maidment et al. say "Spicomellus was added to the thyreophoran phylogenetic matrix of ref. 1, along with Jakapil, Yuxisaurus, Stegouros, Patagopelta, Thyreosaurus, Yanbeilong, Bashanosaurus and Beiyinosaurus, which were all described after that work was completed. The scores for Antarctopelta were also updated based on ref. 9. These taxa were scored from the literature. One character was modified to better reflect morphological variation observed across the ingroup..."  You may remember reference 1 as Raven et al.'s 2023 analysis of ankylosaur phylogeny which I pretty harshly criticized (while also getting some things wrong!) here- https://theropoddatabase.blogspot.com/2023/05/raven-et-al-2023-on-ankylosaur.html . Well, how does this update involving two of the four 2023 coauthors hold up?

You gotta go to Figure S12 in the supp info to see the result, but the first thing I notice is that they deleted taxa a posteriori to reveal the underlying topology, which I said they should have done back in 2023 instead of just showing the numerous polytomies. So that's good! Also, while they never explicitly say so, they don't use Raven et al.'s invalid definition for Polacanthinae/-idae based on Gastonia instead of Polacanthus, because Gastonia isn't in their Polacanthinae, but Polacanthus is. So, also good! Similarly, instead of using a Panoplosauridae ("All ankylosaurs more closely related to Panoplosaurus than to Ankylosaurus, Struthiosaurus austriacus or Gastonia burgei") which includes Nodosaurus, they correctly use the older Nodosauridae. Methodological improvements all around.

How does Raven et al.'s main conclusion hold up, which from their abstract was "The traditional ankylosaurian dichotomy is not supported: instead, four distinct ankylosaur clades are identified, with the long-standing 'traditional' clade Nodosauridae rendered paraphyletic. Ankylosauridae, Panoplosauridae, Polacanthidae and Struthiosauridae have distinct morphotypes..."  Well, Polacanthus, Gastonia, Struthiosaurus and Panoplosaurus are all nodosaurids, so the traditional consensus wins. Indeed, in 2023 they said "Within Nodosauridae, there are three groupings of taxa: 'polacanthid' ankylosaurs, but excluding Polacanthus; a 'panoplosaurid' group typified by Edmontonia and Panoplosaurus; and a 'struthiosaurid' group typified by Struthiosaurus and Hungarosaurus." But the Polacanthinae in Figure S12 is not the group they recovered in 2023 including Sauropelta, which is instead that grade of nodosaurids from Zhejiangosaurus to Sauropelta, and in fact their Polacanthinae here is Raven et al.'s Struthiosauridae with Polacanthus at its base. And ankylosaurids sensu lato themselves are no longer necessarily monophyletic, with shamosaurines in a trichotomy with ankylosaurines/-ids and nodosaurids.

Speaking of which, Maidment et al. recover Spicomellus as a shamosaurine, but never use the term Shamosaurinae. Seems pretty unlikely to me when it's Bathonian but other shamosaurines are Barremian or later. It's based on two characters- "70 (0): Dorsoventral height of the pterygoid process of the quadrate greater than 0.5 times the height of the entire quadrate. Convergent in Ankylosaurus and Gastonia burgei. 190 (1): Coracoid glenoid length is 0.5 to 1 times as long as scapula glenoid length. Convergent in some polacanthines, Texastes, Scelidosaurus, Tuojiangosaurus and Stegosaurus stenops." Can't say I'm convinced. But then there's a lot of weird things in their tree, like Cedarpelta being outside Eurypoda, Yuxisaurus being a stegosaur but huayangosaurids are even further from Eurypoda than Cedarpelta, Middle Jurassic Chinese Tianchisaurus breaking up Late Cretaceous European Struthiosaurus and Middle Jurassic European Dracopelta breaking up Late Cretaceous North American Edmontonia. In an analysis meant for determining thyreophoran relationships, that seems off. Either something went wrong with those taxa or it should be big news.

Unfortunately, after the unweighted tree, we get the extended implied weights analysis, where they do things backward and exclude the taxa that were pruned from the unweighted tree, THEN ran the matrix under implied weighting (K= 3). But deletion of taxa with unique combinations of characters a priori is always bad, and who knows if those taxa would have made the same polytomies under implied weighting. The topology is so different that I doubt they all would have. It looks better in some ways, like Cedarpelta is an ankylosaur again and huayangosaurids are stegosaurs (although weirdly deeply nested so that e.g. Dacentrurus and Tuojiangosaurus are outside Huayangosaurinae plus Stegosaurinae), but now Mymoorapelta is outside Eurypoda (at least it's Jurassic) and Jakapil is sister to Hesperosaurus!? Dracopelta's in the same bad spot, but now Tianchisaurus is a deeply nested polacanthine. Spicomellus is still a shamosaurine, requiring even more (12+) ghost lineages since now nodosaurs are a paraphyletic grade leading to ankylosaurids. And we were so close to maintaining the correct nomenclature, but NOOO Figure S13 has Nodosaurus in Panoplosauridae. Sigh.

Mickey Mortimer

[Ben Creisler]

A free pdf is now available in ResearchGate:

https://www.researchgate.net/publication/395014628_Extreme_armour_in_the_world's_oldest_ankylosaur

On Wed, Aug 27, 2025 at 10:09 AM Ben Creisler <bcre...@gmail.com> wrote: