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Re: Mesozoic birds made insects shrink

The problem with using eye-size as a gauge for diurnal or nocturnal habits is 
that visual acuity also pushes eye size up. Hence, while we may assume that the 
enormous orbits of anuroganthids reflect crepuscular/nocturnal habits, they may 
also reflect a general need for superior vision to locate small, mobile aerial 
targets. Many diurnal raptors or insect hawkers have very large eyes for this 
reason, so I'm not sure if we can say for certain that any pterosaurs were 
active in dim light. Anuroganthids would be the best candidate, though.



Dr. Mark Witton
Honorary Researcher
Palaeobiology Research Group
School of Earth and Environmental Sciences
University of Portsmouth
Burnaby Building
Burnaby Road

Tel: (44)2392 842418
E-mail: Mark.Witton@port.ac.uk

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>>> jean-michel BENOIT <mjmbego@gmail.com> 05/06/2012 22:42 >>>
Given the relativley large eyes of pterosaurs, could it be possible that
they evolved a nocturnal lifestyle, like bats, thus avoiding competition
with birds?


2012/6/5 Don Ohmes <d_ohmes@yahoo.com>

> On 6/5/2012 3:53 PM, Mike Keesey wrote:
>  How well do we understand what the evolution of bats meant for birds?
> Have bats pushed birds out of any eco-space since the Eocene?
> My impression is that the answer is "no, they seem to have largely avoided
> direct competition" -- so that might be an easy and cheap way to answer
> that.
>  There is _no_ evidence at all that birds competitively excluded
>> pterosaurs, for instance.
> AFAIK, birds waited until the largest ptero's were long gone to evolve to
> similar sizes, yet there is a very long record of at least bird-ish animals
> co-existing with pteros -- that seems to me like indirect but strong
> evidence further supporting the idea that the old "birds were the invasive
> new-comers that doomed the old guard" scenario is not a good fit to the
> geo-record.