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Re: Fwd: Warm-Blooded debate

I've resubscribed Paul and put him on vacation (as per section 5 of
the administrivia message) in the hopes that after the two messages
included below I won't have to do this again.  Keep in mind that the
next time you see a message from Paul he still may not be receiving
the list.  As a final note, I'm not all that pleased with the
dismissive nature of the last message.  Please don't hold me
responsible for its content.  I will pass that sentiment along to
Paul as well...  If you chose to flame him for it please do so


Mickey Rowe     (mrowe@indiana.edu)

Date: Tue, 1 Jul 1997 19:46:17 +1100
To: dinosaur@usc.edu
From: pwillis@ozemail.com.au (Paul Willis)
Subject: Re: Fwd: Warm-Blooded debate

Once more, thanks again Mary.

>It is in fact true that crocs are hard pressed to combat mammals after the
>initial rush.


This is a big generalisation that is easily swamped by the huge variety of
variable parameters. Substrate condition, ambient tempreture, condition of
the croc, condition of the prey, relative sizes of the croc to the prey,
etc., etc,., will all have effects on how hard a croc will press and attack
and form the attack will take. While wildlife documentaries do like to show
big crocs leaping out of the water, biting a large mammal on the bum and
holding on until the prey dies or escapes, this does not represent the full
range of croc hunting strategies. Some smaller crocs will press an attack
if the prey (mammalian or not) is big enough to subdue but not big enough
to require unwarrented effort. In such cases, crocs will let go for the
chance of a better grip, particularly where the substrate does not favour
the prey. Really small crocs, such as Paleosuchus and Osteolaemus, have
been observed having quite prolonged, complicated struggles with larger
prey items (including mammals).

So, while the above observation may be generally true in particular
circumstances, it is not generally true across the crocodiles and across
the range of prey types and environmental settings. What is possibly does
represent is prejudiced view of what ought to happen in encounters between
ectotherms and endotherms.



Dr Paul M.A. Willis
Consulting Vertebrate Palaeontologist
Quinkana Pty Ltd

Date: Tue, 1 Jul 1997 19:46:22 +1100
To: dinosaur@usc.edu
From: pwillis@ozemail.com.au (Paul Willis)
Subject: Re: Fwd: four chambered croc hearts

Thanks once again to Mary

>>While the "fully erect" bit is almost certainly correct and the "wholly
>>terrestrial" is probably correct, what fossil evidence is there that
>>protosuchians and other early crocs had a four-chambered heart?
>   Deduction rather than actual fossil record.  Extant crocs have a
>physically four chambered heart that is functionally three chambered.
>Crocs' closest living relatives, birds, have four chambered hearts.  It is
>possible that the physically four/functionally three chambered heart is the
>archosaurian condition, but given the erect limbs of early crocs hinting at
>an active, terrestrial existence this suggests a need for a four chambered
>heart.  Further, one would think pterosaurs would have needed a four
>chambered heart for an active flying lifestyle.  Counting the croc heart as
>four chambered, if the four chambered heart was not an archosaurian trait
>then it evolved independently three times among archosaurs.  Parsimony
>dictates that we pick the simpler explanation, that the four chambered heart
>was inherited by the three groups from their common archosaur ancestor.
>This would mean that early crocs had a four chambered heart.

This has all the hallmarks of fuzzy crap. These are not deductions but
speculations and should not be confused with good solid facts such as
fossil evidence for physical characters.



Dr Paul M.A. Willis
Consulting Vertebrate Palaeontologist
Quinkana Pty Ltd