  A main issue in cosmology and astrophysics is whether the dark sector
phenomenology originates from particle physics, then requiring the detection of
new fundamental components, or it can be addressed by modifying General
Relativity. Extended Theories of Gravity are possible candidates aimed in
framing dark energy and dark matter in a comprehensive geometric view.
Considering the concept of perfect scalars, we show that the field equations of
such theories naturally contain perfect fluid terms. Specific examples are
developed for the Friedman-Lema\^itre-Roberson-Walker metric.
