What is "callulina"

Callulina (commonly known as the warty frogs) is a small genus of frogs in the family Brevicipitidae with nine members in Tanzania and Kenya. Originally Callulina was thought to be monotypic and widely distributed through Eastern Arc Mountains in Tanzania and in southern Kenya. However, within the last decade eight new species has been identified, the majority of which are considered critically endangered by the International Union for Conservation of Nature (IUCN).