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Re: birds and pterosaurs



I think taphonomic processes are partly responsible for this observation.
 Inland environments tend to be brutal on delicate fossils.  And although
birds have relatively delicate bones compared to other vertebrates, my
observation is that the bones of pterosaurs are even more delicate.  The
long bones of pterosaurs have a thickness (measured from the exterior
surface to the medulary cavity) of two chicken egg shells.

In contrast, coastal plain environments and marine environments have a
lot of standing water which tends to protect the fossils prior to their
burial.  The exceptions to this are beach environments.

The Hell Creek Formation is a coastal plain unit that contains a large
number of fragments of birds, while the first pterosaur from the
Formation was reported only a few years ago.  Terror Lizards are by no
means common in the Hell Creek Fm. (although this may also be related to
their declining diversity and population numbers during the latest
Maastrictian).

<pb>
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On Sat, 08 Oct 2005 14:21:14 -0400 brushes2@juno.com writes:
> In their article "Pterosaur diversity and faunal turnover in 
> Cretaceous
> terrestrial ecosystems in China (Nature437:875-879) Wang, et al., 
> discuss
> ecological relationships between pterosaurs and birds. They occur
> sympatrically and both fly. the authors suggest "...that the avian 
> fauna
> of the Lower Cretaceous--and perhaps most of the Mesozoic era--was 
> more
> confined to terrestrial, inland regions, whereas pterosaurs 
> dominated the
> coastal areas." They worked in the Yixian formation.
> 
> While speculative, this is an interesting observation suggesting
> ecological specialization of two flying groups.
> 
> Cheers,
> 
> Alan
> Alan H Brush
> brushes2@juno.com
> 92 High Street
> Mystic, CT. 06355
> (860) 572-1717
> 
> 


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