The corpses of water-dwelling animals often sink to the bottom and become covered with sediment. The sediment tends to protect the dead body and even at times retain an impression of its shape and external anatomical details. This environment then provides the means by which the bones of the skeleton are mineralized.... most land animals die and fall to the ground, without any chance of a freak flood casting them into an environment more favorable to fossilization.

What the Bones Tell Us (1997)