re: Sauropods and lung development

[Scott A Hartman <ottscay@uwyo.edu>]

>>>Would global CO2 levels and anatomic dead space in sauropods have any
relationship on lung development/evolution in these dinosaurs?  I'm
thinking
specifically of the type of lungs that modern birds have when I ask this.

Michael Teuton        <<<

     If global CO2 levels were significantly different, then that may
indeed have had an impact.  However, the scientific communitee doesn't
exactly seem to have formed a consensus on the subject as of yet.  There
is very good histological evidence (see Reid's paper in _The complete
Dinosaur_ for references) for sauropod pleurocoels being pneumatized.
It's hard to imagine what other than an air sac system would be present.
Long necked extant birds like flamingos clearly get around the dead air
space problem (this is partially do to the efficiency of a unidirectional
lung flow, and partially due to the efficiency of air storage and
expulsion by the airsacs themselves).  But rather than suggest that dead
air space in sauropod necks lead to the evolution of air sacs,  I think
it's more parsimonious that the common ancestor to sauropodomorphs and
theropods already had a primitive (and non invasive) air sac system, which
allowed sauropods to radiate into niches that required a long-necked
morphotype.  Interestingly, outside of of the Saurischia (avian and non),
there are very few terrestrial animals that evolve long necks.

Scott Hartman