Re: (Fwd) Large Dino Growth

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

>>Such
>> forest giants are much harder to plow over.  (However, the Morrison
>> climate was so arid, I doubt such large trees were very common,
>> really).
>>
>This last makes me wonder - just what vegetation was there in sufficient
>abundance to feed the Morrison denizens, given such an arid climate?  They
>certainly were able to find food, but away from the river banks, what could
>grow in sufficient abundance and replenish itself sufficiently rapidly to
>support a sizeable population of veggiesauruses?  :)

Recent advances in the paleobotany of the Morrison show that, for most of
the Late Jurassic, the Western Interior was much wetter than has been
considered for most of the last fifteen years (but drier than the swamps
imagined several decades ago).  Over 350 species of plants, maybe half of
them ferns, have now been identified by pollen.

(Note that the Morrison Formation is one of the largest known in areal
extent, and formed over about 10 million years.  There are particular
intervals and particular places which show evidence of strong aridity;
there are also evidence of extensive vegetation in other regions and
intervals.  Both generalizations, swampy or arid, probably hold true for
some of the Western Interior for some of the late Oxfordian-to-early
Tithonian.  Overall, though, it seems like it was at least seasonally damp
for most of the region for most of the time).

[These results courtesy of palynologist Ron Litwin {USGS}, presented at the
Morrison Conference last year.  These abstracts are available (somewhere),
but the volume is not yet published.]

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.