Re: PARTICULAR sauropods aquatic?

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

DinoGeorge and Dan Varner bring up some points to consider with the manus 
dominated sauropod prints.  If these were underprints, as Lockley says, why 
should the manus prints be deeper?  Excellent point to bring up.  Here are 
two ideas to ponder on further:

1. I would suspect (although I may be wrong) that an animal walking through 
the mud and sediment underwater would produce very vague trackways.  This is 
because as the foot is drawn out of the wetter sediments, the sediment is 
sucked back together leaving a very weird and vague mark, but nothing like 
what we see in the manus-dominated tracks.  If memory serves, there are 
mammoth tracks that show this sort of soupy-suck-back thing -- someone have 
a ref?  This might suggest that the heavier hind feet sucked the sed back 
into place, obscuring their tracks, while the less-heavy forefeet were 
retained more or less?  But, this would be at odds with the few good pes 
tracks we have that show change of direction.

2. What if the sauropod was walking downhill?  It's manus (the plural of 
manus is spelled the same with a line over the "u" and pronounced: manoos; I 
know this from Jack McIntosh) prints would then possibly be imprinted deeper 
into the mud than the hindfeet, therefore supporting Lockley's underprint 
idea.  Do we know the dip of the bedding plane or anything that might clue 
us in to that possibility?

Another possibility is that even though sauropods were lighter in front than 
back, the more narrow and "pointed" manus distributed force worse than the 
splayed hindfoot, therefore making deep prints by physical default.

Jerry Harris mentioned the apparent absence of great lakes.  If we are 
looking in the Morrison Formation, particularly the Brushy Basin Member or 
the latest part of the formation, we have evidence of relatively dry 
conditions and anastomosing (joining) stream systems.  While there was water 
available, it doesn't appear that in North America much was in the form of 
large fresh water lakes.

Krzic's amusing story on the waterfowl was much appreciated! =)

Martin Barnett's observation of the differences in fore to hindfeet being 
due to bipedal ancestry are noted.  While most sauropod workers that I am 
aware of see sauropods as descendants of bipedal dinosaurs (me among them) 
one should give pause to consider the quadrupedal scenario that Charig et 
al. proposed in 1965. It would be more difficult, however, to understand how 
such great differences between the manus and pes would have resulted in 
sauropods if this were the case.

Marching on ...
Matt Bonnan

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