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Re: Deinonychus claw use and origin of flapping



Anthony Docimo <keenir@hotmail.com> wrote:

>  which dodges the question of what they did before their family could fly.


No, it doesn't dodge the question at all.  We can't assume that the
ancestors of birds were arboreal *before* they could fly.


> it's one of the earliest origin-of-dinosaur theories I ever heard of   (in 
> both senses of "early")
>
>  basically, dinosaurs evolved from something semi-aquatic like a croc, which 
> grew longer and longer hind limbs (for swimming? i
> don't recall), until it was bipedal.


I haven't read this paper.  I'm betting _Lagosuchus_ hasn't read it either.


>  you don't have to be specialized for something  in order to deal with it.


Negotiating steep, unstable terrain such as steep cliff where one slip
means plunging to your death... nah, I think you *do* have to be
specialized for this.


>  elephants can swim - that isn't because they're specialized for life in the 
> water.


Elephants probably aren't the best example of your analogy; the
earliest members of the Proboscidea were probably aquatic.


>  dinosaurs dominated terrestrial niches throughout the Jurassic and 
> Cretaceous and at least part of the Triassic.  just as
> pterosaurs ruled the Mesozoic skies (later time-sharing with birds), and just 
> as marine reptiles ruled the seas, dinosaurs ruled the
> land.


It think your editorial isn't giving sufficient credit to
non-dinosaurian diapsids, or to synapsids such as mammals.  There is a
difference between "dominate" and "monopolize".  If we are careful
about definitions, it could be said that dinosaurs "dominated"
terrestrial niches through most of the Mesozoic.  But I'm sure there
were plenty of terrestrial niches that remained devoid of dinosaurs.
Besides, terrestrial niches during the Mesozoic weren't always the
same as those that exist today.


If we are going by numbers of species, and limiting ourselves to
metazoans, then arthropods ruled the land during the Mesozoic.  They
still do.


> and given that the ground is almost never smooth and uniformly even*, animals 
> have developed the ability to handle
> themselves on uneven terrain.


Two things:


(1) Goats are specialized for this lifestyle, because those goats that
live in steep, scree-ridden terrains have to contend with a *very*
challenging environment.


(2) I've no doubt that dinosaurs (the non-avian kind) could handle
themselves on uneven terrain.  But the terrain that many goats have to
contend with represents a whole new level of "uneven".  No good can
come from comparing dinosaurs to goats.







Cheers

Tim