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Re: Yet more on pterosaur quad arm posture



Gregory S. Paul <GSP1954@aol.com> wrote:

> It is sheer fantasy to keep Microraptor primarily on the ground. High res
> photos of numerous central toe claws (and all the rest) shwo they are
> strongly arced in the manner found only in birds that do not walk much on the
> ground.


This particular metric is not yet known for larger dromaeosaurs (such
as _Velociraptor_ or _Deinonychus_).  So alone it doesn't mean very
much.


> All modern birds that walk a lot on the ground have flatter claws, I've
> looked at them all (there are not really that many of them) plus previous
> published data.


All well and good.  But did large dromaeosaurs typically have flatter
claws, or are they strongly arced like those of _Microraptor_?  In
short, when it comes to pedal claw curvature among dromaeosaurs is
_Microraptor_ the exception, or the rule?

I know we don't know the answer to this question, because we don't
have preserved keratinous claws for large dromaeosaurs.  But until we
do, we're discussing _Microraptor_ in vacuo.


> That makes sense since sinornithosaurs lived in heavily forested habitats,
> and their enromous foot feathers would have hindered walking and been
> damaged doing so.


I don't need to rebutt this straw man of an argument; Dececchi and
Larsson (2011) have already done it for me:

    "The presence of long feathers on the tibia and tarsus of nonavian
    paravians has been cited as evidence for a four winged
    gliding origin of flight and an arboreal stage in avian evolution
    [13,16]. It has been argued these feathers would have interfered
    with terrestrial locomotion which would have induced feather
    damage [9]. This argument fails to account for the fact that even if
    _Microraptor_ was an arboreal animal it would have to move within
    the branches (either as a biped or a quadruped), thus engendering
    the same degree of damage as in a terrestrial setting."


> Even assuming basal dinofliers could take off from the ground does not mean
> they were not arboreal. Almost all arboreal birds can take off from ground.


I only mentioned it because the impetus for putting little paravians
in trees often comes from those who argue that the origin of avian
flight *must* have been "trees-down".  It would be nice if the issue
of arboreality in theropods was evaluated separately from the issue of
the origin of flight in theropods.  The two are often treated as
effectively synonymous, which is not helpful.






Cheers

Tim