Type signatures are common in modern linguistic theories. Their construction and maintenance is intricate, and therefore, an automatic induction method is desirable. In the present paper we present FCAType, a module of our system FCALing, that automatically induces type signatures from sets of untyped feature structures. The induction procedure is based on so-called decomposition semilattices which serve as a basis for initial type signatures. These signatures can be folded up to result in compact and restrictive type signatures which adequately specify the input structures.