[Elsie]

Sediment covered the animal while it was sleeping or resting on the ground, burying the animal alive. This is unlike most fossil animals which die and decompose or are scavenged before burial.

Try pouring a big bunch of sand or something on a sleeping bird, and just SEE if it stays in that postition to die!

[Reaganwuzthebest]

No one knows for certainty yet how dinosaurs may have slept but the similarity in bone structures is definitely there.