To be concise:
New research has suggested that Birds, Bats and flying Dinosaurs were
able to take to the skies, due to a surge in oxygen levels in the
atmosphere. This happened during the mid Jurassic era, when O2 peaked
at ~26%...through on to the Cretaceous and Tertiary. Apparently the
reappearance of Giant Insects occured at this time too. The extra O2
would have helped vertebrates muster the energy for flight, along with
the air being denser, making flight easier.
cheers
J.
James Cracknell - Dedham Vale, (Stour Valley) Suffolk England UK
james@iceni.prestel.co.uk www2.prestel.co.uk/iceni
Pager: 04325 378866