The Marciak are large musteline carnivorous mammals with long, flexible spines. They were equally comfortable with traveling on all fours or upright. Most Marciaks were infertile females. One in every hundred was male, and five in every hundred were fertile females. Marciaks lived in clans called "septs," always headed by a female. Septs were organized into dens, which were made up of sterile females and a small number of breeder males and females.