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As an alternative to an arboreal origin, I think there is
none equal to it. [Which isn;t saying much].
> Can you suggest any other evolutionary advantage other than insect
> capture which would lead to the evolution of flight feathers in a
> cursorial biped?
Not that I find at all reasonable.
Note, body feathers are a very different thing than flight feathers,
and they most probably evolved as insulation in support of endothermy.
> I don't find this convincing evidence for a cursorial hypothesis.
> thing, bipedalism and occupying the same niches could lead to
> forms in the hindlimbs of birds and late Cretaceous theropods.
Actually, origin from a cursorial biped by way of an arboreal
biped would also account for it. Bats and the like originated
from arboreal *quadrupeds* (this is probably even true of
pterosaurs, via things like Sharovipteryx).
That is an arboreal form that is derived from a bipedal ancestor
would likely retain the fundamental bipedal posture in the trees.
Thus, I currently favor an arboreal origin of flight from
aroboreal, bipedal theropods.
> >It's good to know that Alan knows the whole of dinosaurian
> >those of us who work on them still find strange new morphotypes
> >years :-)
> I think Alan's point here is that there are no documented arboreal
> characters in theropods in the fossil record (other than possibly
> of Archaeopteryx if you call it a theropod).
Strictly speaking this is true, though arboreality doesn't always
have clear anatomical indicators. Tree squirrels are little
different than ground squirrels, for instance.
Also, there is no question but that the fossil record of small
theropods is abysmally incomplete - almost as incomplete as our
record of fossil birds. [For instance, most fossil birds are
aquatic forms, often rather specialized aquatic forms, and in
most cases the nearest ancestral forms are not known at all]
Thus, it is rash, at this time, to make *any* definate statements
about the diversity of small theropods. We keep finding unexpected
new forms of small theropods, often quite different than any known
before. Until the rate of discovery of major new variants slows
down, we need to be careful in saying something doesn't exist.
[Note, for instance, that most new discoveries of larger dinosaurs
fall into one of the known anatomical groupings - even if it is a
> Aren't dromaeosaurids physically larger than Archie?
This is highly variable - the smaller troodontids (similar to
the dromaeosaurids) are not much larger than Archie.
> In contrast to
> Archie, dromaeosaurids lack flight feathers, sharp toeclaws that
> closely resemble those of modern perching birds(Feduccia), and
> posture (unless Martin's reconstruction is flawed).
Given the already cited problems with Martin's reconstruction,
I will give you two out of three.
[Though it is rash to assume that dromaeosaurs had no feathers
at all; it is also rash to assume they *did* have feathers].
> But if Archie spent so much time running around on the ground, why
> the points of his toeclaws look like a roadrunners(i.e. worn). IMHO,
> neat Jurassic manicure job is consistent with the arboreal theory
> contradictory to the cursorial theory.
In my opinion, this is one of the best pieces of evidence for
an arboreal (or at least "bush-dwelling") Archie.
The peace of God be with you.