What are microfossils?
Microfossils are small fossils that require microscopy for observation and study. These include small organisms as well as endo- and exoskeletons, the embryos of larger organisms, and also small pieces of bone and other hard material from larger organisms. Fossils much smaller in size that require high power microscopy for their study are called nanofossils. Some of the microfossils can be referred to as index fossils due to their wide distribution and large quantity. They are very useful for making stratigraphic time measurements. Certain microfossils may be an index for a paleoenvironment that can help in the study of paleoecology. In addition, many fossil specimens may be obtained from a small microfossil sample, making the microfossils a great material for the study of morphological evolution.
Common microfossil include Radiolaria, Foraminifera, Ostracoda, and the Conodonta. Radiolaria and Foraminifera are primitive microorganism; Radiolaria secret an outer shield of silica, while Foraminifera secret calcium or build an outer shell of sediment cemented together. Ostracods are crustaceans that have a bivalve exterior shield similar that of mollusks. Where the Conodonts belong in the evolutionary chain is unclear. They were once considered to be microfossils from the bones or organs of marine animals already extinct, as their appearance is similar to that of the teeth of certain fish or the mandibular organ of an Annelid and so they are named as such. These tiny hardened shields and bones are easily preserved in sediment where they become fossilized.