Re: Mysticete evolution (was Re: Speculative dino species)

["João S. Lopes Filho" <jodan99@uol.com.br>]

A good and fascinating book about speculative evolution is Dougal Dixon's
"Beyond the man". He creates an hypothetical world 50 millions of years in
the future.
For example, he guess that penguins will evolve to whale-like creatures.
----- Original Message -----
From: christian farrell kammerer <cfkammer@midway.uchicago.edu>
To: David Marjanovic <david.marjanovic@gmx.at>
Cc: The Dinosaur Mailing List <dinosaur@usc.edu>
Sent: Tuesday, July 31, 2001 8:31 PM
Subject: Mysticete evolution (was Re: Speculative dino species)


> On Sun, 29 Jul 2001, David Marjanovic wrote:
> > I've read a very simple explanation for this in Carl Zimmer's book At
The
> > Water's Edge: Macroevolution and the Transformation of Life: Baleen
whales
> > evolved when the loop of cold currents closed around Antarctica, which
> > produced the present enormous amounts of krill. So we should expect
> > _something_ (something endothermic, according to HPs Paul & Leahy) to
become
> > a giant filter feeder at that time (early Oligocene), but not before.
>
> I've read this too, and while it's an interesting idea, I'm quite
> skeptical. If this were the case, one would expect the most primitive
> mysticetes to be found in the Southern Hemisphere, but with only a few
> exceptions (most of which, I might add, are from the Pliocene, thus making
> them too late to play a part in this debate) the cetotheres (ostensibly
> the most basal balaeniferous [is that a word?] mysticetes) are Northern
> Hemisphere creatures, with many representatives in Europe, Asia, and North
> America but few if any from the supposed epicenter of mysticete
> evolution. Also, the cetotheres, especially the early ones, were small
> whales (some less than 20 feet)--hardly "giant" filter feeders. Also, true
> giant filter feeders in the form of the whale sharks were around at least
> as early as the Eocene--how does the Antarctic solution explain their
> evolution? Whale sharks conceivably arose from some form of generalized
> orectolobiform in the Cretaceous, yet no reptiles followed suit. Finally,
> a brand spankin' new paper on krill evolution (I don't have the ref handy,
> but I can find it) claims that, based on molecular data, the swarming
> krill family Euphausiidae dates back to the Early Cretaceous. If this is
> true (and admittedly, there's a good chance it isn't, and even if so, we
> can't know the behavior of ur-krill for sure), then why weren't the
> Cretaceous reptiles taking advantage of it? Perhaps they were, albeit not
> in a mysticetimorph form? Who knows, maybe the closest reptiles got to
> suspesion feeding was in things like Aristonectes. Now if only we could
> figure out what Shonisaurus was eating back in the Triassic...
>
> -Christian Kammerer
>