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Re: the supracoracoideus system and bird flight



>From: Jeffrey Martz <martz@holly.ColoState.EDU>
 >   I'd like a little clarification on exactly what sort of depositional 
 > environemtn the Solnholfen limestone is and how the Archaeopteryx'x
 > ended up there.  I've kind of had the impression that the Solnholfen
 > were a series of offshore islands, and the Archaeopteryx and
 > pterosaurs and all the other nifty critters were oreserved in a lagoon
 > between the islands and the mainland.  Is this even remotely correct?

Aproximately.

The Solnhofen itself is the *lagoonal* deposits.  It was a more
or less stagnant lagoon, with anoxic bottom waters.  It preserved
a great many fossils - mostly of marine animals: fish, ichthyosaurs,
and similar beasts.

There really was no "mainland" - all of Europe was a bunch of islands
at the time.  I believe that the lagoon was between an outer coral reef
and a large island.

>From time to time, due to various causes, a land animal would float
out into the lagoon, and get buried along with the marine stuff. These
land animals include such things as Compsognathus, one of the smallest
known dinosaurs. In this regard Archaeopteryx is not all that unusual,
just one more land animal that died and ended up floating in the lagoon.

 >      I'm asking to try and get a better idea of what the Archaeopteryxs 
 > were doing there, particularly if they were supposed to be arboreal.  
 > I've heared two ideas:
 > 1) The Archaeopteryxs were living on the islands (or at least visiting 
 > the islands) and died nearby, in the lagoon.

Note the islands were on the *land* side of the lagoon, not the
seward side.  Also, they may have entered the lagoon *after* death,
by floating down stream during the rainy season.

 > 2) The Archaes were living inland on the mainland, died and fell in a 
 > river, and got washed out to the lagoon.

The "mainland" was just a large island.

In all probability both scenarios happened from time to time.

 >      Also, It seems more likely to me that the Archaeopteryx died very 
 > near the lagoon, possibly falling right into it when they died or at 
 > least dying on the beach and getting washed in, simply for the reason 
 > that I find it hard to beleive that a little fragile animal like 
 > Archaeopteryx could get washed a ways down a river and end up often 
 > (usually?) with minimal disarticulation and feathers relatively 
 > unrumpled by the time they reached the lagoon. 

Actually, before serious decay sets in they would break up very little
while floating. Whole carcasses can be moved quite some ways by river
action.

Also, "inland" need only have been a couple of miles, or perhaps
a few tens of miles.  These islands were at most a few hundred
miles across.

 >      Also, how common is Archaeopteryx relative to other tetrapod 
 > species like pterosaurs and Compsognathus at the Solnhofen?

It is more common than Compsognathus (seven versus at two or three
specimens).  It is less common than Pterodactylus. But then I think
Pterodactylus (or at least some species of it) may have been the
Mesozoic equivalent of swallows, which I have seen swooping about
above a lake catching insects, and even dipping into the water to
catch water-striders and the like.

 >  I mean 
 > counts of individual species, not a percenatge of the total number of 
 > species.  In other words, what does its rarity or commonality say 
 > about if it was a rare an accidental visitor, or a native of the 
 > area?

It is rare enough compared to Pterodacylus to make it an occasional
relative to P.  Even P. is rare compared to the marine fossils,
however. 

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.