[dinosaur] Adult Ankylosaurus immune to T. rex attack?

[Poekilopleuron <dinosaurtom2015@seznam.cz>]

Good day! Most books about dinosaurs state that adult Ankylosaurus magniventris 
(and other ankylosaurs for that matter) were practically immune to attacks from 
large tyrannosaurid theropods. But was it true? Of course ankylosaurids were 
tough and uneasy prey with their body armour and tail clubs, but they were also 
slow and not very clever animals. Could adult T. rex perhaps turn ankylosaurus 
body over (with its strong legs) and than kill it with bites to its abdomen? 
Thank you for your thoughts! Tom