Sedimentary rocks
Rocks formed from deposition of materials ("sediment"), usually by water (lakes, seas, rivers), but sometimes by wind (deserts). The depositional environment can be characterized by it’s levels of oxygenation and energy. A high-energy environment is one in which the water is fast-moving and agitated, able to carry particles of large grain sizes; typically this occurs in shallow lakes & seas and in rivers, as well as deserts. Conversely, a low-energy environment is one in which the water can be very deep and quiet; it can only carry the finest grain sizes (if any!). The oxygen levels in the depositional environment correlate roughly with the energy levels (high-energy = high oxygen); high-energy water is well-agitated and contains much oxygen, whereas low-oxygen water is usually low-energy (either deep, or stagnant, as in some ponds and lakes).
Clastic sediments
Consist of fragments (clasts) of pre-existing rocks, which have been transported and deposited by physical processes (e.g. sandstone, mudstone).
The grainsize depends almost entirely on the water energy (high-energy => large grainsize). Dinosaur bones are most likely to be found in clastic sediments.