That's more interesting as the reasoning of PaulK. Do you mean that genes for such behaviour were inherited from dinosurian ancestors and were somehow switched on?
crocodilians and basal archosaurs seem to have buried their eggs, and used tempurature to control gender. i'm not too clear on early dinosaurs, though the transition from cold-blooded to warm-blooded seems to have occured prior to dinosaurs' divergence, within crocodilians like postosuchus.
dinosaurs as a whole seem to have continued using egg-mounds, though in various different styles. i seem to recall that both ornithischians and saurischians tended their eggs in open nests, but that sauropods (unlike other saurischians) buried them due to the impracticality of sitting on them.
in other words, in this particular evolutionary tree, egg-burying came and went a few times (much like flight). tempurature's relation to gender might be common to the whole lineage, and egg burying may simply be a common solution for controlling temperature.
Edited by arachnophilia, : No reason given.