Did theropods dream of armoured sheep?

Sophie the Stegosaurs, mounted in the NHM and floodlit with silver light.  There is a person in the background to give scale to her.

I had a 'free' afternoon, having a morning in the office that day and an evening meeting in London.  I cleared it with my Team Leader that I'd take the afternoon out  and I made my way to the Natural History Museum to look at the fossil marine reptiles.  After I'd spent quite some profitable time perusing those, I made sure I had a good look at Sophie, the most complete Stegosaurus ever found and the only one on display in Europe. Steggies are my favourite dinosaurs (yes, I'm a grown-up with a favourite dinosaur. I'd bet you a tube of fruit pastilles that I'm not the only one!) so visiting her was a must.

After you have been awed by her size and her plates, the one thing you do notice is that she has a tiny 30cm-ish (about 1 foot in British terms), narrow, head in relation to her size. The species name, S. stenops, actually highlights this.  On a balcony overlooking the skeleton, the NHM have a clear Perspex model of a Stegosaurus' skull, and this has a coloured model of the brain inside it.  The brain is about the size of a plum.

I remember reading, far longer ago than I would like to admit, that steggies had two brains - one tiny one in their heads and another one near their pelvises.  Current thought is that the 'second brain' was more probably a glycogen body, so their tiny brains, at well under 100g each, were all they had by way of grey (and while) matter. 

Yes, they were predated by theropods (hunter-killer dinos), and yes, they defended themselves with their tail spikes (known as thagomisers, but that's another story).  There is fossil evidence of an injury to an Allosaurus caused by a steggie using its tail spikes in self-defence, but their anatomy does also suggest that they were no Einsteins.  They were dim, they probably roamed in herds and they grazed.  A bit like armoured sheep in a way.  Now, I like sheep and I see many more sheep and cattle than I do people most weeks, but it does have to be said that they're not the brightest animals on the planet.  Sheep brains weigh in at about a comparatively large 140g, by the way.

Again, yes, Sophie is an amazing specimen; when I look at this photo, I still feel the awe I felt when I was standing in front of her.  Allosaurus were probably not so impressed, but I bet that they dreamed of hunting Sophie and her kin.

Yes, if you followed my earlier blog on this site, you will have read about this photo before.  Sorry (not sorry) 😊 - it bears another look.

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