Paleocene dinosaurs

Paleocene dinosaurs describe families or genera of non-avian dinosaurs that may have survived the Cretaceous–Tertiary extinction event 65.5 million years ago. Although almost all evidence indicates that dinosaurs (other than birds) all went extinct at the K-T boundary, there is some scattered evidence that these non-avian dinosaurs lived for a short period of time during the Paleocene epoch. The evidence for Paleocene dinosaurs is rare and remains controversial.

Evidence

Several researchers have stated that some dinosaurs survived into the Paleocene and therefore the extinction of dinosaurs was gradual. Their arguments were based on the finding of dinosaur remains in the Hell Creek Formation up to 1.3 metres above (40,000 years later than) the K-T boundary. Similar reports have come from other parts of the world, including China.cite journal|author=Sloan, R. E., Rigby, K,. Van Valen, L. M., Gabriel, Diane|date=1986|title=Gradual dinosaur extinction and simultaneous ungulate radiation in the Hell Creek formation|journal=Science|volume=232|issue=4750|pages=629–633|url=http://www.sciencemag.org/cgi/content/abstract/232/4750/629|doi=10.1126/science.232.4750.629.|accessdate=2007-05-18]

Recently, there is possible evidence of a Dead Clade Walking: in 2001, evidence was presented that pollen samples recovered near a fossilized hadrosaur femur recovered in the Ojo Alamo Sandstone at the San Juan River indicate that the animal lived in Tertiary times, approximately 64.5 million years ago or about 1 million years after the K-T event.cite journal|url=http://www.lpi.usra.edu/meetings/impact2000/pdf/3139.pdf|title=Compelling new evidence for Paleocene dinosaurs in the Ojo Alamo Sandstone, San Juan Basin, New Mexico and Colorado, USA|author=Fassett, JE, Lucas, SG, Zielinski, RA, and Budahn, JR|date=2001|journal=Catastrophic events and mass extinctions, Lunar and Planetary Contribution|volume=1053|pages=45–46|accessdate=2007-05-18] Many scientists, however, dismiss the "Paleocene dinosaurs" as re-worked, i.e. washed out of their original locations and then re-buried in much later sediments. [cite journal|last=Sullivan|first=RM|title=No Paleocene dinosaurs in the San Juan Basin, New Mexico|url=http://gsa.confex.com/gsa/2003RM/finalprogram/abstract_47695.htm|journal=Geological Society of America Abstracts with Programs|volume=35|issue=5|pages=15|date=2003|accessdate=2007-07-02] A compelling argument against re-working would be a complete or at least associated skeleton (e.g. more than one bone from the same individual) found above the K-T boundary. As yet no such finds have been reported.

Analysis

Footnotes