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Re: Perching, climbing, roosting was Re: 11th specimen of Archaeopteryx



> -- The 2nd toe of dromaeosaurids was able to be flexed very far. It
> may well have been used to hold branches against the metatarsus,
> all else being equal -- but all else wasn't equal. There's a reason
> why the huge claw is called "sickle claw": it's flattened from side
> to side, and its very narrow palmar edge, while blunt on the ungual
> bone, may have supported an outright cutting edge on the horny
> sheath in the living animal. Cutting off the branch on which you
> sit brings the Darwin Award to mind. Unfortunately, no keratinous
> claw of a dromaeosaurid is preserved in 3D as far as I know.

 I am agnostic on sickle-claws, at least as related to trees. Cutting
 of branches while sitting on them isn't gonna happen, though.

How do you know?

> -- Any species that climbs trees and stands around in them for
> evolutionary significant spans of time -- say, a few decades --
> will show adaptations to this.

 Why? Are your feet evolutionarily adapted to sleeping in a bed?

No. That's why I put one of those roll-shaped pillows under them. I sleep on my belly, you see, and I'm not adapted to keeping my angles extended to 180° for hours.

Lying on my back squeezes my calf and gluteal muscles too much, even on soft mattresses, straightens my vertebral column too much, and means I have to lift my entire belly (at least that's how it feels) to breathe. Clearly, I'm not adapted to that either.

> -- Conversely, grasping feet -- including feet shaped by
> compromises between grasping and walking/running -- may not have
> grasped any plant matter, but prey.

 Seems logical enough. Or both, or versa...

Don't shift the goalposts.

> -- 300-lb rednecks are _better_ suited for climbing trees than
> *Archaeopteryx* was. Sure, their weight is a massive disadvantage,
> I presume they're wearing shoes, and they have laughably short
> toes; but they've got amazingly flexible hands, insanely mobile
> shoulders, forearms that can rotate through about 180° (and that's
> before we consider rotation of the entire arm at the shoulder
> joint), hips almost as mobile as a lizard's, rotatable lower legs,
> ankles that allow tilting of the feet, a long, flexible vertebral
> column, and a dorsoventrally flattened ribcage with the remarkably
> mobile shoulder blades on its dorsal side. Do not project primate
> -- or even "just" general mammalian or indeed general amniote! --
> anatomy into dinosaurs. Do not take it for granted; not everyone
> has it.

 Steel climbing claws are commercially available -- should you
 actually try them, you will find your primate flexibility and
 mobility are actually undesirable, and that you spend all your time
 making short vertical motions w/ your arms more or less extended,
 hands in the thumbs-up position, and your feet in approximately the
 same orientation as when standing at the tree-base.

 Left-hand up, right foot up, right hand up, left foot up, repeat...

Doesn't remind me of any theropod.

 Claw-ed trunk-climbers and hand-ed primates are apples and oranges.

There are plenty of claw-climbers without opposable digits around today. They're all mammals and squamates. Compare them to Archie and weep.

> -- So far, I don't see a reason to assume any climbing or roosting
> in any dinosaur that wasn't able to fly into a tree.

 Ah! So you are strictly a "ground-upper", then? Tell me how you
 manage that, in the face of a limited wing-stroke?

Did you react last time I posted this http://www.dinosauria.com/jdp/archie/feather.htm ?

 I note yet again -- should the 'limited wing-stroke in pre-birds'
 contention be dis-proven, then the trunk-climbing capabilities of
 Archie-type animals are less relevant to those of us who wonder how
 birds became such wonderful fliers.

Oh, definitely.

 Expecting a vociferous debate on the validity of 'limited
 wing-stroke' to start, imminently... Silly me.

Well, really, I don't understand why you expected that. Anatomical facts are anatomical facts. We can't debate them -- except for those of us who have seen the fossils and studied that question on them, and I'm not one of those few people.

> *Confuciusornis* may be an exception, but it had moderately
> grasping feet, huge curved claws on the 1st and 3rd fingers, an
> enormous deltopectoral crest on each robust humerus, and IIRC
> shorter legs than Archie, especially shorter lower legs; it was
> clearly better at trunk-climbing than Archie, even if not much.

 Interesting.

Interesting? Interesting is the fact that you didn't know that. Have you never seen a photo of *Confuciusornis*? The features I mentioned are glaringly obvious, they're not tiny details that might not show on a coarse-grained image. Even the monographic description, Chiappe et al. (1999), can be downloaded for free because it was published in the AMNH Bulletin.

You have a responsibility to educate yourself on what you're talking about.

> -- Why climb into a tree for safety rather than hide under a
> shrub?

 Because it is safer...

...right after I explained that it's not safer as far as I can see. What have I overlooked?

Trampling is only an issue in landscapes accessible to big animals. Any sufficiently dense forest isn't such a landscape.