Final answer:
The statement that almost all dinosaur fossils are found in sedimentary rocks is true. Sedimentary rocks facilitate the preservation of fossils due to their layers, aiding rapid burial and reducing decay and scavenging.
Step-by-step explanation:
Most dinosaur fossils are indeed discovered in sedimentary rocks. This is due to the way sedimentary rocks form, by accumulating in layers over time which can bury and preserve biological material. As organisms, such as dinosaurs, die and become covered by layers of sediment, these layers can eventually harden into rock, encasing the remains. The preservation of fossils within these rocks depends on certain conditions; one such condition being rapid burial, which sedimentary environments, such as river deltas or floodplains, often provide.
Environments not suitable for preserving fossils would include ones where biological material is exposed to the elements, scavengers, or to physical wear that prevents fossilization. Moreover, sedimentary rocks are broadly used for biostratigraphic correlation, where fossils found in these rocks, especially index fossils, can provide precise geological dating and environment information. Fossils, such as belemnites, can date rocks to specific eras like the Mesozoic.