Conodonts (figure 2) are also microscopic fossils that can be extracted from rocks by dissolving the rock in strong acids. Their biological identity was discovered to be from the skeletal remains from the feeding apparatus of an extinct group of marine worm-like animals that lived from 570 to 200 million years ago (Howell, 1993). Since, conodonts are found with other fossil assemblages a time scale was able to be established of changing conodont morphology. For rocks greater than 250 million years old the basis for radiolarian biostratigraphy is occasional joint occurrence of radiolarians and conodonts.
By the discoveries of these two fossils and how to extract them from rocks allows for geologists to use biostratigraphy as a means to date
By the discoveries of these two fossils and how to extract them from rocks allows for geologists to use biostratigraphy as a means to date