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Mesozoic forests (was predator relationships)



 Chris Campbell wrote:
 > <snip>
 >  Some of your old growth forest is quite clear of underbrush
 > and low limbs, so a _T._rex_ might have done fine there.  

 Dann Pigdon <dannj@alphalink.com.au> wrote:
> This would have been especially true in the Mesozoic, with all of
> those large herbivores around. I always thought that the trees
> featured in many dino reconstructions were giant tree ferns,
> until I happened to notice the growth pattern at the top of
> a live araucarian and it suddenly hit me: those pictures were
> probably of araucarians that had been "pruned" by sauropods. I
> suspect that if tyrannosaurs followed large herds of herbivores
> around, that the prey themselves may have cleared the forest
> areas of low lying branches.
 
Actually, if we're on the same page (so to speak), you may rather be seeing
tree ferns in those illustrations.  They have the characteristic look of a
palm tree in general appearance, but (unlike palms) have typical fern
foliage with an abundance of tiny leaves on each branch.  Extant genera
include _Cyathea_, _Alsophila_, and _Hemitelia_.  You can see them today in
New Zealand (as seen on TV in <Hercules> and <Xena>) among other places.

Within the extant Araucariaceae we now have four species:  _Araucaria
heterophylla_, the Norfolk Island Pine; _Araucaria araucana_, the Monkey
Puzzle tree from Chile; _Araucaria bidwilli_, the Bunya Bunya Pine of
Australia; and the recently discovered _Wollemi nobilis_, the Wollemi Pine
of Australia.  The "araucarians" you refer to are perhaps the monkey
puzzles which may form a "lollipop-shaped" array of branches at the top (in
mature specimens).  The tough, spiny leaves which cover these high branches
may be one reason for the name, "monkey puzzle," as the tree would not be
easily climbed by a monkey.  On pp. 146-7 of David Norman's book,
_Prehistoric Life_, you can see the sort of "pruning" that some of the
sauropods might have practiced on these trees, namely, flattening the trees
whose branches proved to be just a bit out of reach.

The leaf types and toxins associated with living gymnosperms (whose
ancestors made up the dominant terrestrial flora before the advent of
angiosperms in the mid-Cretaceous) presents a puzzle in itself.  The
foliage of ferns and of the dawn redwood would seem to be the easiest to
consume.  That the Mesozoic was populated by an array of vegetarian
behemoths is testimony to the ability of the dinosaurs to adapt to their
environment.  What species of megafauna today could subsist on pine
needles?  And yet, there they are, inside the belly of the _Edmontosaurus_
mummy.  Amazing!

For modern reconstructions of Mesozoic landscapes, I direct you to
_Dinosaurs: A Global View_ by Sylvia and Stephen Czerkas (ISBN
0-7924-5606-8), breathtakingly illustrated by Mark Hallett, Douglas
Henderson, and John Sibbick.  It even includes a plant appendix which names
most of the featured plants.  For younger readers, Don Lessem's _Dinosaur
Worlds_ (ISBN 1-56397-597-1) does a nice job of portraying ecosystems past.

Ralph Miller III <gbabcock@best.com>

"Latest fossil finds fuel controversy among scientists.  Film at 11."