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Re: Dinosaurs vs. mammals: a hypothetical scenario



2011/4/8 Raptorial Talon <raptorialtalon@gmail.com>:
>
> True, though again, the predators large enough to threaten
> non-nestling dinosaurs are the ones most in question; viverrids and
> mustelids in the Miocene would have been pertinent to very small
> dinosaurs, but for the larger dinosaurian herbivores, it would be
> felids, barbourofelids, amphicyonids, hemicyonids, borophagines, and
> hyaenids that would have be the major causes for concern.

Most of the modern fastest mammalian predators, canids and felids, are
relatively small in size (fox-wild cat-sized) to harm non-avian
dinosaurs which were not quite small, and mostly do not go after
ungulates in their size range, but after rodents. This suggests to me
that predator velocity may not be so closely related to coevolution
with fast running prey.

Many of the Miocene large carnivores likely were not mostly cursorial,
according to one
thesis(http://biblioteca.universia.net/html_bura/ficha/params/title/aspects-of-locomotor-evolution-in-the-carnivora-mammalia/id/50826002.html).
Thus, they may have attacked youngs which were not so much fast, as
bears do with fawns. So, it seems to me that the velocity of a fast
prey may not imply an increase of velocity in the predators, and thus,
not necessarily in herbivorous competitors. Thus, for example, in
Africa not all the mammalian prey is fast, even if some prey is very
fast.
>
> Sure, but if cursoriality is itself a proxy for competitive
> superiority in the Miocene (regardless of the specific biomechanical
> factors), then only relative degrees of such adaptation in dinosaurs
> vs comparably-sized mammals need be compared for our purposes here.
>
"If". Formerly I mentioned some problem regarding the possibility of a
need of velocity. Second, we agree cursorial limb elongation may also
represent an advantage in foraging by saving energy. But some long
limbed animals are not good runners, for example the maned wolf, the
seriema, humans (relative to other catarrhines), elephants (relative
to other large mammals) and old world camels, yet they have a relative
advantage in energy-saving while foraging, so both things do not need
to be equated. And we can say that if the energy saving factor plays a
significative part, dinosaur bipeds can have compensation relative to
quadrupeds with longer limbs by moving just two limbs.