Re: Stegosaurs: why did most of the species die out before the end?

["T. Michael Keesey" <mightyodinn@yahoo.com>]

--- frogfoot <frogfoot@ntlworld.com> wrote:
> 
> This question has been bugging me for a long time actually.  The first few
> dinosaur books I ever got were still of the days when Stegosaurs had these
> plates for armor protection.  I guess that its well established that they
> used them for regulating body temperature now, or differentiating between
> species?

We don't really KNOW what they were used for. Protection, thermoregulation, and
display (intra- and/or interspecific) are all still possibilities. Might even
have been used for all of these purposes. Granted, stegosaurian plates/spikes
aren't as effective at protection as ankylosaurian armor, but they still look
like they would have protected the vertebral column pretty dang well.

OOC, are there any studies comparing plate shape to size? It seems like smaller
might mean spikier and bigger might mean flatter, which could lend credence to
the thermoregulation idea.
 
> The only Stegosaur I know that was around til the end of the Cretaceous is
> Dravidosaurus.  Only a handful of others made it into that same era.  So what
> happened to them, climatic change, different predators/food?

_Dravidosaurus_ is now known to be a plesiosaur - one of the stranger
misidentifications among fossil tetrapods. _Wuerhosaurus_ (Early Cretaceous) is
now the latest known stegosaur, IIRC.

I don't think it's known exactly why they died off during the Cretaceous.
Perhaps competition from other ornithischians better equipped to deal with 
angiosperms.

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