I think that I've had my fair share of cryptozoology and anecdotal evidence. Things don't have to be gigantic or monstrous or poorly supported to be interesting. Being incredibly unusual helps though. I remember reading Walker's Mammals of the World a while back and coming across a strange account of a species of shrew able to withstand a man standing on it with no ill effects. An accompanying picture showed an absolutely bizarre spinal column with "armor" mostly on the thoracic vertebrae. With the magical power (to me) of access to journals both home and abroad, I've been able to track down the supremely named Hero shrew, Scutisorex somereni Thomas 1910.
Despite being so strange, the unique spinal morphology wasn't recognized until 7 years after the shrew was described and little information was learned for the next 80 years (Cullinane et al., 1998). There seems to be a long history of interesting things being found in Museums, of all places. Scutisorex was hypothesized to be related to the genus Sylvisorex judging by dental characteristics, although molecular evidence suggested that it diverged from Sylvisorex cf. konganensis and S. ollula in the mid-late Miocene (Querouil et al., 2001). The paper notes that the morphology of shrews is difficult to interpret clade-wise, so a polyphyletic genus is not a surprise - the possibility that the hero shrew is not even a distinct genus is shocking. The spinal column is remarked upon as being the most modified among vertebrates (Cullinane & Aleper, 1998); that evolving within a genus would be astounding. More molecular studies will probably clarify the position of the hero shrew, but regardless it seems that the unique spine evolved very suddenly. Something definitely punctuated the equilibrium here.
So what exactly is so unique about the hero shrew's anatomy anyways? Wikipedia's image demonstrates that this armored shrew is completely unremarkable looking externally and looks roughly similar to anythi
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipiehkjgOg-_0JDUi7T0cNLMZy3ZElbkFvs5EGGSaGZhq5OXUfUqfHoR9K3oGd74g-rL8-2NuCeNX9Kre498EFIUj1l-ja9uznMiM_tp0XjFLUb1a8lTw-_XVWseWc-3YPQR2k5XbCwM0d/s400/S.somereni.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgU3DDr4Jc1mBLGt3AMDWS7jTTGky9hhdeCB-n57JkzeAwFDoAqk6EWZcgQXRuUaGReOkg1E0Uq_LYBfeZ4LycXCF36n6wz6rwR0kp2nl7XqQGjpBHQTqE47JoCvkpQq0l6tcUfauS6k53a/s400/heroshrew.jpg)
Why this species has such a modified spine is a mystery. The species is only present in the Eastern Democratic Republic of Congo and neighboring Rwanda, Burundi and Uganda where it is not common (and rather elusive) (Churchill et al., 2007). Churchill et alii's study attempted to determine the spinal modifications by determining its diet and thus determining its habitat. This large shrew species was found to be opportunistic but focused on earthworms, a rare trait for an African shrew but common in large temperate species. With its unspecialized limbs and diet, it was determined to be a partially subterranean (not fossorial) feeder, like many other shrews. The only possible specialization for this way of life was an unusually long digestive tract (possibly to digest worms), although the spine/rib modifications were not explainable.
Cullinane & Bertram wondered that if there were no known behavioral or ecological correlation to this structure, which there don't seem to be, then "perhaps complex morphologies can evolve without selection driving their adaptive trajectory." This is a rather astounding idea, what if the cause of the bizarre spine morphology is nothing more than a few simple mutations? Does it give any benefits to this species? Since it is noted as being uncommon, perhaps it doesn't...or perhaps it is recent enough that benefits are not entirely apparent. Maybe if given enough time this could evolve into a distinct group of mammals - Cullinane et al. 1998 conjecture that "this species may represent a breakthrough in the morphology of the tightly constrained structure that is the mammalian spine". That is an awfully exciting idea, a future radiation of mammals started by the Hero Shrew! Or not, it could always be an evolutionary dead end, a bizarre evolutionary "experiment" of sorts. If this truly did evolve within a genus, or at least very closely related to species, then it may represent an absolutely fascinating case study in punctuated equilibrium.
I can tell that something is up with me that I'm more far excited by this shrew than the notion of a super-gigantic-snake-mimicking-Amazon-archeocetes or whatever. What have I become...
References:
Churchill, S. 2007. Feeding ecology of the armored shrew, from the north-eastern Democratic Republic of Congo. Journal of Zoology 273, 40–45. Available: Here
Cullinane, Dennis M. et al. 1998. The functional and biomechanical modifications of the spine of Scutisorex somereni, the hero shrew: skeletal scaling relationships. J. Zool., Lond. 244, 447 -452. Available: Here
Cullinane, D. M. & Aleper, D. 1998. The functional and biomechanical modifications of the spine of Scutisorex somereni, the hero shrew: spinal musculature. J. Zool., Lond. 244, 453-458. Available: Here
Cullinane, Dennis M. & Bertram, John E. A. 2000. The mechanical behaviour of a novel mammalian intervertebral joint. J. Anat. 197, pp. 627-634. Available: Here
Querouil, Sophie et al. 2001. Phylogeny and Evolution of African Shrews (Mammalia: Soricidae) Inferred from 16s rRNA Sequences. Molecular Phylogenetics and Evolution. Vol. 20, No. 2, pp. 185–195. Available: Here
Cullinane, D. M. & Aleper, D. 1998. The functional and biomechanical modifications of the spine of Scutisorex somereni, the hero shrew: spinal musculature. J. Zool., Lond. 244, 453-458. Available: Here
Cullinane, Dennis M. & Bertram, John E. A. 2000. The mechanical behaviour of a novel mammalian intervertebral joint. J. Anat. 197, pp. 627-634. Available: Here
Querouil, Sophie et al. 2001. Phylogeny and Evolution of African Shrews (Mammalia: Soricidae) Inferred from 16s rRNA Sequences. Molecular Phylogenetics and Evolution. Vol. 20, No. 2, pp. 185–195. Available: Here
13 comments:
How did people first discover that you could stand on the shrew without hurting it? Is that one of the checkpoints they have now?
Anyways, I think that those shrews are going to be the building blocks of the future, future floors that is.
I also assume that being called a hero will force the shrew to wear a cape at all time, except for when it's doing some new paper reporting, then it has to put on some glasses....
Anyway, this was a very interesting blog, without having anything gigantic, scary, or nonexistent, excellent job.
Speculation has it that the spine structure represents an adaptive response to the perils of foraging beneath particularly heavy rocks and logs.
Yeah, I was just going to say what byssus already did. Hero shrews can withstand taking a lot of weight on the back - not much good if a big rock falls on you, as you're still trapped, but it might prove useful in levering up stones when foraging. And some literature says that they do lots of foraging in streams where such a trick might be useful (I mentioned this in an article on amphibious murids: here).
There are wonderful Drawings in vol 1 (I think-- I'm not going into the freezing library!) of Jonathan Kingdon's African Mammals.
Just found this blog. Very cool articles you've written, and I'll be checking back again! Keep it up.
Hi, they have found another shrew called "Thor's Hero Shrew" - apparently it is another amazingly strong-spined creature. Named for Thor the God because of its strength and for a scientist with the nickname of Thor. For more look it up on Wikipedia.
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