Notice: This is an archived and unmaintained page. For current information, please browse

Why There Were Dinosaurs; Why There Are Birds

Presenter: Peter Ward, University of Washington
When: November 18, 2003 12AM PST

New information on the levels of atmospheric oxygen
through the Phanerozoic indicates that the end of the Permian and end of
the Triassic were times of greatly lowered oxygen compared to the present
day, equivalent to the oxygen content at current altitudes in excess of
12,000 feet. Here I propose that the combination of low oxygen and
repeated short spikes in global temperature caused by methane induced
atmospheric greenhouse conditions that were the primary causes of the P/T
and T/J mass extinctions. These lowered oxygen levels, which according to
the models persisted through the Triassic and into the early Jurassic
(with minima at 250 and 200 Ma) may well have lead to the evolution of
bone pneumatization found in modern birds and most lineages of saurischian
dinosaurs examined to date. New physiological studies of this system in
extant birds shows it to be far superior to the respiratory systems of
lizards, amphibians, and mammals in surviving at high altitude (and thus
lowered oxygen). It also appears that vertebrate lineages with this
newly-evolved respiratory system had higher survival rates across the T/J
mass extinction interval than did lineages with the air-sac system.

To join using a videoconferencing system:

Please RSVP to Mike Toillion ( if you will be joining by Polycom.

To view the slides, connect to

To join using a web browser:

The slides and audio/video for this meeting will be presented using Adobe Connect. To join the meeting, connect to:

If you are having problems connecting, you can try joining, or rebooting your computer, or try joining from another network.

University of Washington Seminars

  • The University of Washington seminar series is hosted by the NAI Virtual Planetary Lab (VPL) team live from the University of Washington campus in Seattle.
  • Subscribe to this series

Other Seminars in this Series