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Re: Dinosaurs vs. mammals: a hypothetical scenario



2011/4/8 Raptorial Talon <raptorialtalon@gmail.com>:
>>As far as I know, most dinosaur bipeds had cursorial proportions for
> their size.
>
> I was a bit ambiguous there. I meant *in cases* where cursorial
> adaptations are clearly lacking in one and present in the other. What
> I had in mind, in the context of that paragraph, was things like
> pachycephalosaurs, small ceratopsians, and perhaps some of the
> stumpier small ornithopods. Those critters weren't lumbering tortoises
> by any means, but compared with a *Miohippus,* gazelle-camel, or
> dromomerycid, those sorts of dinosaurs don't seem notably well-adapted
> for sustained fast running in open terrain.

Ok., but then we may say that the less cursorial bipedal dinos would
not be more outcompeted than the less cursorial mammalian quadrupeds
of the same size (because also in the Cenozoic you have non-cursorial
quadrupeds living along with cursorial quadrupeds). We should compare
the most cursorial quadrupedal mammals with the most cursorial bipedal
dinosaurs.

> Especially since
> quadrupedal running is generally more energy-efficient than bipedal
> running due largely to superior stride length, if I'm not mistaken
> (although at the opposite end of the spectrum, bipedality is more
> energy-efficient for walking because fewer limbs are expending
> energy).
>
Is there a source stating this? Because I would rather think stride
lenght to be variable among both bipeds and quadrupeds, and can mind
long-legged bipeds having a stride advantage over many quadrupeds with
proportionally shorter legs. In addition, moving two legs instead of
four while running looks to me like more energy-efficient also in
running (because of the same reason you mention, expending energy in
moving two extremities instead of four).