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Re: Cost in Aquatic Birds
Thanks for the long post... quite something to discuss :-)
> whereas the dromaeosaurs of the Jehol
> biota has given credence to the trees-down theory.
I don't think so.
> There are excellent arguments for both.
There are also excellent arguments against both. (Still waiting for the
paper on vertical running...)
> Problematic to these is the idea that for some reason, *Archaeopteryx*
> pectoral anatomy was insufficient for sustained flight, much less powered
> flight, and proponents of this include Ebel who proposed an aquatic-thrust
> capability for *Archaeopteryx* to somehow _perfect_ the thrust generator
> of the wing for flight.
> Problematically, there are several morphological
> features in aquatic birds that *Archaeopteryx* does not have. [...]
Again I don't think Archie could qualify as aquatic. Just as semiaquatic as
> and studies by Yalden [on Archie's feet]
> support these were in fact arboreally suited, were not
> tailed but strongly clawed.
Other studies disagree to varying extents. Anyway, the toe claws are quite
strongly curved, but the finger claws much more so -- I wouldn't expect that
in a climber --, and Archie's feet aren't good for perching.
> No truly-aquatic bird possesses such feet.
I don't think I need to care what truly-aquatic birds have :-)
> Even wing-powered swimmers have large sternae,
(sterna is already the plural, of sternum)
> and in fact the larges sternae and keels in birds belong to the purely
> [...] This is missing in
> *Archaeopteryx* (and in fact, only one preserved sterna is known for seven
> specimens) and it is quite small and only incipiently keeled.
Indeed, this sternum is so flat that some have doubted it was enough for any
sort of flight. But the Confuciusornithidae obviously managed to fly around
with sterna just as flat. Pat Shipman: Taking Wing sez the keel "only"
serves to keep the air sacs between the muscles from collapsing, which
allows the heat to be transported away efficiently; the absence of a keel
would just mean the inability to _sustain_ flight for long periods of time.
> Nothing specifically qualifies *Archaeopteryx* for swimming in any way,
> shape or form.
Same for the dipper (except its nostrils) AFAIK.
> Ebel supported *Archaeopteryx* swimming nearly entirely
> based on insignificant flight musculature and the inability to fly from
> small island to small isalnd and still account for the wide-spread
> distribution of the specimens in the Solnhofen Limestone.
> Perhaps an
> analogue would be the flightless cormorant....
...which is a foot-propelled diver.
> However, these are not
> truly advantageous facts to supporting any lifestyle, and the quality of
> the material prevents a cohesive analysis of the fact that *Archaeopteryx*
> possessed robust pectoral musculature ... or marginal ones. Knowledge of
> the environment is insifficient to support small little islands spaced
> well-apart, and these flaws mar Ebel's work.
I am aware that many arguments for FUCHSIA are negative. :-)
> There are few birds that take to the water
> easily and still maintain a non-aquatic life-style. Ospreys are an example
> of a bird that takes hours cleaning and preparing its feathers before a
> fishing dive, and this bird specializes in fish, though it still takes
> other prey.
Do they actually dive? AFAIK only their feet touch the water if the fish
isn't so strong that it can drag the osprey down.
> *Archaeopteryx* displays absolutely no positive data that suggest it was
> in any way aquatic.
It does have the unserrated teeth of a fish-eater, though. And dippers
wouldn't present fossilizable positive data either.