Re: Mesozoic - the heyday of life?

[Jonathon Woolf <jwoolf@erinet.com>]

DSFPortree@aol.com wrote:
> 
> I'm working on another dinosaur script idea for EARTH & SKY radio - seems to
> me that, in many ways, life on Earth took a downturn after the Mesozoic.
> Animals now are generally smaller. Some would argue they're slower, too. They
> don't have as big and varied an arsenal of weaponry, offensive and defensive,
> as did the dinosaurs.
> 
> Of course, nowadays we have humans, and humans have nuclear bombs, stealth
> bombers, and the like, but I'm thinking of non-human animals here. Mammalia
> has never produced anything on the scale of a Brachiasaurus or Tyrannosaurus
> Rex.
> 
> At least that's my impression. I wonder if anyone else has thought about
> this.

I have, on more than one occasion.  I think the Mammalia actually come
out of the comparison quite well.  Consider:

When did the dinosaurs rise to prominence?  Answer: Mid- to Late
Triassic, say about 220 to 210 MYA.  

When did the first "mega-dinosaurs" appear?  The really big sauropods,
the giant theropods, etc.?  Answer: Near as I can tell, the megadinos
are all Mid to Late Jurassic, 160MYA and younger.  

Now, note the time in between.  Fifty to sixty million years between
_Eoraptor_ and the first megadinos.  How long has it been since mammals
first rose to dominate the ecosystem?  Answer: Sixty million years, more
or less, not including the time required for all groups of life to
recover after the as-yet-unexplained terminal Cretaceous extinction.

Up til twenty thousand or so years ago, much of the planet was dominated
by megamammals: mammoths, giant rhinos, giant bison, sabercats, dire
wolves, etc.  Another megamammal fauna was devastated by the Oligocene
extinction, including _Indricotherium_ and several others which were the
largest mammals ever to walk the earth.  Seems to me that the Mammalia
has been doing pretty well at producing megafaunas.  And who knows what
might have happened in the future if not for the double-barreled blast
of Ice Age and human hunters?

I might also add that as far as I can tell, the mammals have produced
more variety in sixty million years than the dinosaurs did in a hundred
and fifty million.  I don't think our furry cousins have anything to
feel inferior about at all.

-- JSW