Amazing Convergence: Crustacean vs. Aetosaur

Wow! Check out this blog post at Amphidrome on an amazing (I think) extant gammaroid crustacean from Siberia. I will be damned if the anterior portion of the carapace on Acanthogammarus is not a dead ringer for the cervical armor of the Triassic aetosaur Desmatosuchus spurensis (see Parker, 2008)! Especially check out the last photo on the post (and reproduced below) and compare to the postcard photo of the Petrified Forest mount. Note that the proposed purpose for these structures in the crustacean is defensive, whereas I have argued recently that such spines in aetosaurs may also be used for species recognition and display (Parker, 2007).

Very cool crustacean. Where can I get one? ;)

top photo is from here.


Parker, W.G. 2007. Reassessment of the aetosaur ‘Desmatosuchuschamaensis with a reanalysis of the phylogeny of the Aetosauria (Archosauria: Pseudosuchua). Journal of Systematic Palaeontology 5: 41-68. doi:10.1017/S1477201906001994

Parker, W.G. 2008. Description of new material of the aetosaur Desmatosuchus spurensis (Archosauria: Suchia) from the Chinle Formation of Arizona and a revision of the genus Desmatosuchus. PaleoBios 28:1–40.


  1. Why wouldn't it be defense for the aetosaur? Ridiculously cool convergence, though!

  2. That's pretty remarkable. If there were definitive evidence that the spines serve a particular function in the gammaroids, would it be reasonable to infer a similar function in Desmatosuchus? Too speculative?

    At any rate, I think both of them would make awesome Kaiju.

  3. Steve,

    That would be my guess now as well. Obviously aetosaur armor provided a degree of protection however in modern crocodiles the armor also provides support for the vertebral column during locomotion. When I reconstructed Rioarribasuchus in 2007 I determined that the spines were at the base of the tail and curved forwards, thus were of little use defensively. This suggested some other use, which I extrapolated to Desmatosuchus as well. However, if an extant organism with a similar structure uses it for defense then it would be plausible to extend this to Desmatosuchus.


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