The parts of animals that are rarely preserved unburied are soft tissues such as:

* Muscles

* Organs (heart, lungs, liver, etc.)

* Skin

* Blood

* Fat

These tissues are highly susceptible to decomposition by:

* Scavengers like vultures, hyenas, and insects who quickly devour them.

* Bacteria that break down organic matter, releasing gases and leaving little behind.

Hard tissues, such as bones, teeth, shells, and sometimes scales, are more likely to be preserved because they are less palatable to scavengers and more resistant to decomposition.