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Fwd: Long Necks (was Sauropod ONP)
Here's Mark's post:
Back to informed speculation again, but I think that the long-term success
of the sauropods as a group could have been a result of (no pun intended)
their flexibility, both environmental and anatomical. Although from the more
recent studies (Retallack, 1997, Foster, 2003), based on paleosol analysis and
taxonomic frequency Morrison (and possibly Tendaguru) diplodocoids and
macronarians seem to have had broad habitat preferences, both types existed in
large geographic area that apparently swung between mild seasonal aridity and
wet, humid conditions for long periods of time. If this was the case, local
abundance and availability of plant food items would also be affected.
with their worldwide distribution and prevalance over most of the Mesozoic, it
suggests sauropods as a group had to be adaptable in their diets. They
probably couldn't specialize too rigidly on any one food source, and for too
a period of time.
This is where long necks were a great adaptation. If the "horizontal sweep"
feeding mode was effective in garnering such ground forage as ferns, aquatic
vegetation and other low-growing forms during the season(s) when these were
abundant, it could also have meant survival in the times when these were
scarce, and the tallest conifer and ginkgo foliage/ fructifications/bark may
been best, or perhaps only accessible, by reaching way up-- not only
quadrupedally, but if necessary, bipedally and tripodally as well in the case
diplodocoids. This is where the extreme ventriflection we see in Diplodocus and
Apatosaurus for me makes sense: in an upright position in which the neck was
nearly vertical, foraging in a downward/ forward range of motion would ensure
an effective feeding envelope in this situation. Call it the "cherry-picker"
feeding mode. Seen in the context of their great spatial/ temporal range, both
feeding scenarios could have validity in explaning why sauropods were as
successful as they were. Behavioral flexibilty probably had a lot to do with
radiation and evolutionary success of the earlier prosauropods, and their
bigger and later relatives took it to even further specializations.
MARK HALLETT PALEOART
4742 Liberty Rd. South, Ste. 175
Salem, OR 97302-5037 USA
ph: 503.831.1164/cell 503.999.8179