The bio-fossil is a very important and versatile item found in fossil blocks. The most common use of the bio-fossil is to obtain DNA, which is used to create prehistoric creatures. When put in the analyzer, it can yield DNA, sand, bonemeal, cactus green, and occasionally, nothing.
Bio-fossils can also be used as organic material in the culture vat, which transforms DNA into embryos and avian and non-avain eggs. However, at 20 bio-fossils per cultivation session, it is far more efficient to use the other alternatives (such as buckets of milk).
Fossil models are also made with bio-fossils. Right-clicking on the ground while holding a bio-fossil will produce a random species' fossil model. Breaking the fossil model returns the bio-fossil.Lastly, one bio-fossil is necessary to craft an analyzer.