The fossils are defined as the remnants of ancient plants and animals that were buried millions of years ago. The fossils that are found in the present day includes both heterotrophs and autotrophs.
Those organism that can prepare their own food in the presence of sunlight, water and carbon dioxide, by the process of photosynthesis are considered as the autotrophs. They are also known as the producers. Some of the examples of autotrophic fossils are Gangamopteris and Glossopteris fossil plant.
Those organisms that cannot prepare their own food and are dependent on the autotrophs are known as the heterotrophs. Some of the examples of heterotrophic fossils are dinosaurs.
OK so listen erotrophs cannot produce their own food. More than 95% of all living organisms are heterotrophic, which includes all animals, fungi, and most bacteria and protists. They depend on autotrophs and other heterotrophs for food and energy.