MARINE REPTILE EGGS, & CONSTRAINTS

[darren.naish@port.ac.uk]

Regarding my thoughts on constraints in turtle evolution related to 
their retention of ovipary (I said that embryo turtles derive their 
calcium from the eggshell), Leslie Noe wrote...

> I see a break in the logic here; let me add a rider, eggshells derive 
> their calcium from the mother. Therefore can the embryo not 
> derive calcium from the mother instead  of the (secondary source) 
> of the eggshell?!?

Yeah... I don't know. It would be a good idea to find out about 
calcium budgets and skeletal embryology in turtles and other 
reptiles. I'm very poorly informed in this subject and cannot pretend 
to understand it. Anyone?

On possible terrestrial locomotion in metriorhynchid crocs, Leslie 
said..

> Danny Grange (then a research student, at Bristol University), at 
> the SVPCA (1996, University College London) presented a paper 
> entitled 'Locomotion in metriorhynchid crocodilians' (no idea if 
> this was ever published) in which he concluded met. crocs. could not 
> walk on land (based on limb girdle morphology) 

Grange's stuff on metriorhynchid locomotion was not published, and 
I'm afraid he's now out of the palaeo business, sorry to say. I know 
that Dino Frey and a few other people who have worked on/are familiar 
with metriorhynchids did not agree with Grange's views and his 
contention that metriorhynchids were immobile on land was one point 
of disagreement. Note that Dino Frey and Steve Salisbury are doing an 
SVPCA '98 presentation entitled 'Locomotion in metriorhynchid 
crocodiles: 'no gallop' is the only consensus'. 

"You're making a mess"

DARREN NAISH
darren.naish@port.ac.uk