Re: [DMG] Digest for dinosaurmailinggroup@googlegroups.com - 3 updates in 2 topics

[Paul Penkalski]

Mickey Mortimer makes some good points about these recent phylogenetic analyses. Spicomellus certainly isn't sister to Shamosaurus (much less Chuanqilong or Ahshislepelta, if the latter is even valid). The cervical half-rings, among other things, are very different. Erratic relationships like that result from incompleteness, i.e. too few scoreable chars.

As for Ankylosauridae being a trichotomy (did I misread that?), not likely. Ankylosauridae is monophyletic and ankylosaurids are easily discriminated from nodosaurids (provided you have a skull)--see my latest paper:

https://ui.adsabs.harvard.edu/abs/2025CrRes.16606020P/abstract

Ankylosaurids have several neomorphic skull elements that are utterly absent in nodosaurids and polacanthids. Super easy. Hopefully my revision will be out next year.

   Paul P.


On Thursday, August 28, 2025, <dinosaurma...@googlegroups.com> wrote:
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> New Spicomellus fossils from Middle Jurassic of Morocco reveal bizarre oldest ankylosaur - 2 Updates
> Unenlagiidae phylogenetic relationships among Paraves (free pdf) - 1 Update
>
> New Spicomellus fossils from Middle Jurassic of Morocco reveal bizarre oldest ankylosaur
> Russell Engelman <neovena...@gmail.com>: Aug 28 05:49AM -0700
>
> 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.
> On Wednesday, August 27, 2025 at 6:15:02 PM UTC-4 Ben Creisler wrote:
>  
> Mickey Mortimer <therizino...@gmail.com>: Aug 28 05:11PM -0700
>
> 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
>  
> On Thursday, August 28, 2025 at 5:49:30 AM UTC-7 Russell Engelman wrote:
>  
> Back to top
> Unenlagiidae phylogenetic relationships among Paraves (free pdf)
> Ben Creisler <bcre...@gmail.com>: Aug 28 09:28AM -0700
>
> The pdf is now free:
>  
> Free pdf:
>  
> Matías J. Motta, Federico L. Agnolín, Federico Brissón Egli, Sebastián
> Rozadilla & Fernando E. Novas (2025)
> Phylogenetic relationships of Unenlagiidae among Paraves (Dinosauria)
> Journal of Systematic Palaeontology 23(1): 2529608
> doi: https://doi.org/10.1080/14772019.2025.2529608
> https://www.tandfonline.com/doi/full/10.1080/14772019.2025.2529608
>  
> Free pdf:
> https://www.tandfonline.com/doi/epdf/10.1080/14772019.2025.2529608
>  
> Back to top
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[Mickey Mortimer]

Thanks! 

"As for Ankylosauridae being a trichotomy (did I misread that?)"

I meant Ankylosaurinae, Shamosaurinae and Nodosauridae are an unresolved trichotomy in their unweighted tree. Technically that makes Ankylosaurinae become Ankylosauridae because of how phylogenetic nomenclature works, but yeah...

Mickey Mortimer