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Re: propaganda of the majority
>>Aren't dromaeosaurids physically larger than Archie? Presumably, the larger
>>the creature the more difficulty it would have maneuvering in the trees with
>>a stiff tail. Besides, the rigid tail of dromaeosaurids is not in itself
>>a reason to reject their arboreality, it's only one factor. In contrast to
>>Archie, dromaeosaurids lack flight feathers, sharp toeclaws that most
>>closely resemble those of modern perching birds(Feduccia), and semi-erect
>>posture (unless Martin's reconstruction is flawed). The reason to reject
>>dromaeosaur arboreality is the lack of _any_ arboreal characters.
>I wouldn't go that far, and in fact the more I look at it, the less I'm
>convinced that small maniraptorans can be kept out of the trees (after all,
>jaguars and leopards are very good climbers, and are heavier than almost all
>dromaeosaurids). Dromaeosaurids like Velociraptor are fairly small
>(probably jackal-coyote mass), and so weight wouldn't be that much of a
>deterrent. The data isn't in on how much dromaeosaurid toe claws look like
>perching birds, as Feduccia did not examine any dinosaurs in his study. The
>manual and pedal anatomy of Archaeopteryx and dromaeosaurids are very
>similar (except for the sickle-claw of the latter, of course). The posture
>of Archie is still a matter of debate, due to the ambiguities in Martin's
>reconstruction. Finally, we don't know that dromaeosaurids (or almost any
>other theropod) lacked flight feathers, as none have been found in a
>lithographic limestone. I doubt it myself, but the data isn't there to
>argue the point from positive evidence.
I think that most theropods could have gone right up a tree and probably
get up as fast as almost anything given their comparative athleticism.
But this is a non sequitor. Just because Mark Spitz can swim well doesn't
mean he shares a niche with the manatee. Basic survival skills like swimming
or climbing are things that most vertebrates can do to some level. The
question of what lifestyle theropods are adapted for leads most scientists
to a conclusion of theropods being highly adapted to a terrestrial
environment. None of the arboreal characters Sereno cites for Sinornis
have been described for any theropod.
As far as physical size goes, I was referring more to the body length, not
- Sinornis < 1'
- Archie < 3'
- Dromaeosaur 6'
- Troodon 6'
- Velociraptor 10'
- Deinonychus 10'
I'll restate it by saying that it's easier to navigate through trees with
a one foot broomstick out your butt than it is with a 3 foot broomstick.
>>You may not agree that the evidence points to arboreal Archie. Fair enough.
>>The evidence cited to support arboreal Archie is surely not unequivocal.
>>But if Archie spent so much time running around on the ground, why don't
>>the points of his toeclaws look like a roadrunners(i.e. worn). IMHO, His
>>neat Jurassic manicure job is consistent with the arboreal theory but
>>contradictory to the cursorial theory.
>Actually, it would be interesting to see if Bahamian birds which run on the
>beach have significant toe-wear. Archie's Solnhofen environment wasn't much
>like the Southwest, so the effect of substrate on toe-wear should be
>checked. Nevertheless, I will concede that the lack of wear is probably the
>best evidence of arboreality in Archie. However, the sharpness of the
>toeclaws of maniraptoran theropods cannot be tesed in the same manner, since
>(as mentioned above) none have been found preserved in environments which
>would retain the impressions of the horny-part of the claw.
I would suspect that beach runners exhibit a similar wear since quartz
registers 7 on the Mohs scale no matter if it's in the desert or on a beach.
>Indeed, I (and everyone else I know of, for that matter) agree that Sinornis
We have a consensus! Seems like everyone agrees that birds were arboreal
by no later than 135 million years ago. I predict that this date will be
pushed back even farther in future studies.
>Fair enough, and I appologize myself for any disserviice. I, too, enjoy a
>good debate - that is the nature of science, after all. Have any personal
>opinions of the origin of tyrannosaurs... (semi-secret :-) )
I do, but they will have to wait for SVP ;-)