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Troodontid skulls in other nests: the answer



There was a recent feature on Mark Norell in the Wall Street Journal:

http://online.wsj.com/article/SB10001424052702304447804576411911713825824.html

It includes a photograph (the second photograph, halfway down the page) of a 
troodontid nest and one nearly complete hatchling, minus skull. The hatchling 
is IGM 100/1003, and it is assigned to Byronosaurus jaffei. This same material 
was displayed at the AMNH in 2000:

http://www.amnh.org/exhibitions/fightingdinos/ex4.html#

I asked Mark about these specimens and he told me some amazing facts, some of 
which were already published in the 2009 Bever paper on the Byronosaurus 
skulls. He blew away our whole debate on DML about how the Byronosaurus  skulls 
IGM 100/972 and IGM 100/974 could have gotten into the nest of Citipati, 
IGM/979. 

It turns out that the Byronosaurus nest  was collected two years  after the 
Citipati nest, and just two meters uphill and laterally from the famous  
Citipati nest at the Xanadu sublocality of Ukhaa Tolgod. The Citipati nest was 
at the end of a drainage course from the Byronosaurus one, so the troodontid 
material must have tumbled down and come to rest in the depression of the lower 
nest.

When we had our debate about this on DML I entertained several scenarios but at 
one point I suggested that we need not resort to any explanations that included 
biological interaction. By biological interaction I meant scenarios where the 
Citipati fed on perinate Byronosaurus, or vice versa, nor nest parasitism. I 
thought that sheer proximity of nests in a perennially occupied nesting ground 
could explain how debris from one nest lands in another. 

Dr. Norell is preparing to publish this information, including more important 
details, but he is a darned busy guy. I thank him for sharing this preliminary 
information with those of us who were dying to know.


Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544