Catagenesis is an archaic term from evolutionary biology referring to evolutionary directions that were considered "retrogressive." It was a term used in contrast to anagenesis

Anagenesis

Anagenesis, also known as "phyletic change," is the evolution of species involving an entire population rather than a branching event, as in cladogenesis. When enough mutations have occurred and become stable in a population so that it is significantly differentiated from an ancestral population,...

, which in present usage denotes the evolution of a single population into a new form without branching lines of descent. Cladogenesis

Cladogenesis

Cladogenesis is an evolutionary splitting event in a species in which each branch and its smaller branches forms a "clade", an evolutionary mechanism and a process of adaptive evolution that leads to the development of a greater variety of sister species...

is the term used for branching lines of descent; i.e., when the evolutionary origin of a new form is not accompanied by the disappearance of the ancestral form.