Ankylosaurus origins

["Tim Donovan" <msdonovan66@hotmail.com>]

  The rareness of Ankylosaurus was probably due to its preference for well 
inland habitat; AMNH 5895 and even the Scollard specimens may have been 
washed in from the uplands. This is unusual considering the ubiquity of 
Euoplocephalus and may support Starkov's scenario of Tyrannosaurus arising 
well inland in response to Alamosaurus. Perhaps there were different species 
of Euoplocephalus in the lowland and inland environments. The latter may 
have been long exposed to the ancestors of T. rex-something akin to 
Daspletosaurus or T. bataar-which appear excluded from the lowlands in the 
early Maastrichtian. It is possible that only the inland Euoplocephalus had 
time to adapt, giving rise to Ankylosaurus, and the virtual absence of 
ankylosaurids in the Lancian lowlands reflects the habitat preference of the 
surviving lineage and the vulnerability of E. tutus or whatever species was 
present in the upper Horseshoe Canyon.





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