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Re: Paleocene hadrosaurs?










From: bh480@scn.org
Reply-To: bh480@scn.org
To: dinosaur@usc.edu
Subject: Paleocene hadrosaurs?
Date: Sat, 21 Dec 2002 08:37:52 +0000

From: Ben Creisler bh480@scn.org
In case this ref has not been mentioned yet:

Fassett, J, R.A. Zielinski, & J.R. Budahn, 2002. Dinosaurs
that did not die; evidence for Paleocene dinosaurs in the
Ojo Alamo Sandstone, San Juan Basin, New Mexico.
 In: Catastrophic events and mass extinctions; impacts and
beyond. (Eds.  Koeberl, C. & K. MacLeod): Special Paper -
Geological Society of America 356: 307-336. (2002).

AB: Palynologic and paleomagnetic data confirm a Paleocene
age for the Ojo Alamo Sandstone (and its contained
dinosaurs) throughout the San Juan Basin of New Mexico.
The recently reported discovery of 34 skeletal elements
from a single hadrosaur in the Ojo Alamo provides
unequivocal evidence that these bones were not reworked
from underlying Cretaceous strata. Geochemical studies of
samples from several single-dinosaur-bone specimens from
the Paleocene Ojo Alamo Sandstone and the underlying Late
Cretaceous (Campanian) Kirtland Formation show that
mineralized bones from these two rock units contain
distinctly different abundances of uranium and rare-earth
elements and demonstrate that Cretaceous and Paleocene
bones were mineralized at different times when
mineralizing fluids had distinctly different chemical
compositions. These findings indicate that the dinosaur
bone from the Paleocene Ojo Alamo is indigenous and not
reworked. These data show that a relatively diverse
assemblage of dinosaurs survived the end-Cretaceous
asteroid-impact extinction event of 65.5 Ma. The San Juan
Basin's Paleocene dinosaur fauna is herein named the
Alamoan fauna. Magnetic-polarity chronology shows that
these survivors lived for about one million years into the
Paleocene and then became extinct around 64.5 Ma. We
suggest that a plausible survival mechanism for this
Lazarus fauna may have been the large numbers of buried
dinosaur eggs, laid just before the asteroid impact
occurred. These buried eggs would have provided a safe
haven for developing dinosaur embryos for the first one to
two years after the impact, thereby making it possible for
them to survive the worst of the impact's early
devastation.

This is great!Real Paleocene non-avian dinosaurs,even ornithopods! They're gonna have to rework a lot of literature now...


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