The first Catenicellid (Bryozoa, Ascophora) from Mediterranean shallow-waters: a hidden resident or a new immigrant?

Catenicella paradoxa sp. nov. is described from Mediterranean shallow bottoms. Colonies are small, rooted, erect and articulated, each segment either sterile unizooidal or bizooidal, or fertile bizooidal. Basal parts consist of an "articulated basal complex", sometimes related to thick encrusting tubes, invariably followed by morphologically ordinary zooids belonging to each type of segment. The hypotheses of small separate colonies or subcolonies from a network of encrusting tubes are discussed, but relationships with the substratum remain unclear. The species represents the first known Mediterranean catenicellid, a family taxon with a warm, mostly Australasian present-day distribution. Nevertheless, catenicellids and Catenicella species have a long history in the European area from the Middle Eocene to the Early Pleistocene, with at least four different species. In this context, the meaning of C. paradoxa sp. nov. is discussed, bearing in mind problems of species spreading in relation to global warming and human activities.