Based on the characteristics you provided, the artwork that best fits the description is the San Rock paintings at Shelter Cave, Southern Africa.
These paintings were created in caves or rock shelters, used natural pigments derived from minerals and clay, often depicted animals related to hunting, and typically did not emphasize shading for a sense of three-dimensionality. This matches closely with the prehistoric art traditions of the San people.
The other options, such as the Aboriginal cave painting and the Chinese horse painting at Lascaux, are less accurate based on the specifics mentioned. The Lascaux cave paintings, for example, are known for their depiction of animals and more advanced techniques, including some use of shading.