re: PARTICULAR sauropods aquatic?

["Matthew Bonnan" <mbonnan@hotmail.com>]

Boy, you folks sure know how to set out the fly paper for me!  Feet and 
sauropods: that bait works quite well! =)

I don't have much time right now, but let me throw a few things out there.  
First, Riggs back in the early 1900s was the first paleontologist to put 
down in writing the idea that sauropods were terrestrial, this based in part 
on the morphology of feet which are more like those of terrestrial mammals 
than aquatic or semi-aquatic mammals.  He also noted that some sauropods may 
have reared up on their hind legs.  Later, Bakker (1971) and Coombs (1975) 
recapitulated his ideas and revived the notion of terrestrial sauropods, 
this coming quickly on the heals of Ostrom's observations that perhaps some 
dinosaurs were endothermic.

I believe it was Kermac (195?) who showed that the pressure from water on 
sauropod lungs would have caused problems for the animals if they habitually 
were completely submerged.  Comparing sauropods to whales is very 
problematic, not the least of which is the fact that whales habitually dive 
to great depths and have many special adaptations for this that were 
probably absent in sauropods.  I do not know how far the "blowhole" is from 
the lungs in cetaceans, but my guess is that this is shorter than the head 
to lung distance encountered in most sauropods.

Studies by Peter Dodson et al. in the 1980s and continued since by other 
researchers have shown that sauropods are found in many different 
environments ranging from dry, terrestrial to relatively moist.  Personally, 
I have no problem with sauropods wading into water and even feeding there at 
times.  However, completely submerged sauropods would seem to be impossible 
based on the laws of physics as we understand them.

The huge morphological difference in the forefoot (manus) and hindfoot (pes) 
of sauropods sets them apart from elephants which have feet both fore and 
aft that are of similar construction.  The columnar, ring-like structure of 
the metacarpals in sauropods is very interesting and bizarre, even when 
compared to other saurischian dinosaurs.  The phalanges are pretty much an 
after thought in the manus, and it has been suggested that their absence in 
titanosaurs is real (Wilson and Sereno, 1998) and that they never ossified 
in some sauropods.  The big pollex claw ... that's for when I have more time 
to write!

Lastly, juvenile sauropods which were aquatic while they had terrestrial 
parents would seem to be problematic.  Sauropods must have had big appetites 
and may have migrated to satisfy their hunger.  How would the aquatic or 
semi-aquatic juveniles have following the land-lubbing adults?

As I'm sure this thread will continue, more info when I have more time.

Alright, more sauropod feet!

Matt Bonnan

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