Era Period Fossil Assemblage 1. Determine the period(s) of geologic time when this this sedimentary layer was likely formed. 2. What is the "best" index fossil and why? 3. What is the "worst" index fossil and why? 4. If you had only two fossils, which two would give you the age of the sedimentary rock? You don't need to upload your chart - just apply what you know and justify your answers. Specimens: 1 - Favosites (Coral, range Ord-Perm) 2- Composita (Brachiopod, range Miss-Perm) 3 - Juresania (Brachiopod, range Penn-Perm) 4 - Fenestrellina (Bryozoan, range Sil-Perm) 5 - Trepospira (Gastropod, range Dev-Penn) 5 - Trepospira (Gastropod, range Dev-Penn).