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upside down ankylosaurs

At my first SVP meeting in 1976, Dr. Ann Elk presented a landmark hypothesis 
about sauropod morphology. In the same vein, I have been stewing on why so many 
ankylosaur skeletons in North America are found upside down. Charles Sternberg 
(1970, Nat. Mus. Canad., Pub. Palaeon. 4:1-9) ventured the idea that a floating 
carcass would drift upside down because decomposition gases would expand the 
belly. Once the gases vented, the carcass would sink. I had accepted that idea, 
although I modified it because not all ankylosaurs are found in riverine 
sandstone. I have suggested that, like dead armadillos, bloating gases would 
force the legs apart, thereby causing the rotund body to flip the animal over 
(1984, Canad. J. Earth Sci. 21: 1491-1498. 

After many years of diligent research, and monitoring the recent discussions 
(again!) on tyrannosaurs vs. hadrosaurs, I conclude that both Sternberg and I 
were wrong. I suspect what really happened was that roving bands of delinquent 
subadult tyrannosaurs were engaging in ankylosaur tipping at night. 

Kenneth Carpenter, Ph.D.
Curator of Lower Vertebrate Paleontology &
Chief Preparator
Dept. of Earth Sciences
Denver Museum of Natural History 
2001 Colorado Blvd.
Denver, CO 80205

Fax: (303)331-6492
email: KCarpenter@DMNS.org
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