And no, it's not the birth control pill. Here, you have to try this, my friend Nancy said, sliding a yellow tablet to me across her bathroom vanity. No, it wasn't some hot new party drug, but rather, spironolactone, a prescription diuretic commonly used for people with high blood pressureâand sometimes prescribed to women with acne.
Almost all living organisms can leave fossils, but usually only the hard parts of plants and animals fossilize. Soft internal organs, muscle, and skin rapidly decay and are rarely preserved, but the bones and shells of animals are good candidates for fossilization.n this case, the fossil is a hole in the shape of the animal. By far the most common fossil remains are those of shelled invertebrate sea loving creatures such as snails, corrals, and clams. These make up most of the fossil record.
While every fossil tells us something about the age of the rock it's found in, index fossils are the ones that tell us the most. Index fossils (also called key fossils or type fossils) are those that are used to define periods of geologic time. A good index fossil is one with four characteristics: it is distinctive, widespread, abundant and limited in geologic time. Because most fossil-bearing rocks formed in the ocean, the major index fossils are marine organisms. That being said, certain land organisms are useful in young rocks and in specific regions. Any type of organism can be distinctive, but not so many are widespread.