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Re: New refs (short)



Just some thoughts

Nick Pharris wrote:

> Crocs invaded (and still inhabit) a niche (aquatic ambush predation) in 
> which, it has been argued, it is beneficial to be ectothermic.

Did they invade the semi-aquatic niche or did they just evade dinosaurs
on land? In any case crocs are highly adapted to their semi-aquatic niche
including being ectothermic, semi sprawling and having a special blood
circulation system. IMHO they are as highly adapted to living in water as
birds are adapted to flying.

Dinosaurs (as far as we know) never had to adjust to a semi-aquatic living.
Comparing semi-aquatic crocodiles with semi-aquatic dinosaurs, that would
make sense. Would be interesting to know how dinsaurs would have adapted
to this style of life.

Tim Williams wrote:

> Land mammals never got as large as the larger sauropods.  I think that tells 
> us something.

Yes of course, just two possible answers:

1. Sauropods were the biggest dinosaurs. How about ascribing this (among 
other things) to their ability to breathe more effective due to a basal airsac
system.

2. The maximum size of mammals may be limited by the duration of gestation.
The bigger a mammal the longer the gestation period and the lower the
number of offspring at birth. Surpassing a certain size would have been kind of
suicide for a species, because the number of descendants would have been to
low to ensure survival.

Dinosaurs laid eggs and may have been able to grow bigger due to the fact
that there werenât that much adults of giant size to share resources. In sheer
numbers juveniles would have outnumbered adults many times over. This
would also have expanded the size and diversity of the genetic pool and make
large dinosaur species more able to avoid things like the genetic bottle head.
An option not available for large mammal species.

Cheers


Heinz Peter Bredow