Floating parenthetical coordinate clauses

Floating parenthetical coordinate clauses exhibit a challenging behaviour: they disrupt the structure of the host sentence, do not present an overt first term, occur in different positions inside the host clause and, although notionally related to their host, they present syntactic autonomy. Taking into account data from European Portuguese, we claim that these clauses are derived from the core devices of the computational system: the coordinate structure is built up by Set Merge and takes, as first term, a null constituent denoting the host clause; then, Pair Merge operates by adjoining the parenthetical coordinated CP to a functional or verbal projection of the host sentence. Considering the autonomy of the parenthetical clause with respect to its host, we assume that this adjunction is an instance of Late Merge, a counter cyclic operation that applies at PF.