ASPIDYTIDAE: On the discovery of a new beetle family: detailed morphological analysis, description of a second species, and key to fossil and extant adephagan families (Coleoptera)

A new family of adephagan Coleoptera, Aspidytidae, was discovered in China (Shaanxi) in 1995 and in South Africa in 2001. The formal description of the family was based on the South African species. In the present paper we describe the Chinese species, Aspidytes wrasei sp.n., provide a detailed account of the adult morphology of the family and include a key to fossil and extant adephagan families. Members of the family are characterised by a noterid- or dytiscid-likc habitus in dorsal view, a short and laterally rounded, distinctly retracted head, a flat and broad prostcrnal process with straight transverse apical margin and rounded apicolateral edges, a small tuft of spines on the profemora, an exposed scutellum, a short, almost straight internal transverse ridge on the mctaventrite, an almost completely lacking median discriminal line on the metaventrite, comparatively short metacoxae with distinct metacoxal plates, and slender hind legs without swimming hairs. The strongly shortened pedicellus is an autapomorphy of the genus and family. Assignment to Dytiscoidca is supported by the extensive median fusion of the metacoxae, i.e. the presence of a large midcoxal septum. The globular shape of the basal part of the scapus is similar to what is found in Notcridae, and the presence of a profemoral tuft of hairs is another feature shared with adults of this family, but also with adults of Dytiscidae (in part). The complex mesocoxal cavity is a character state shared with Amphizoidae, Dytiscidae (in part), Trachypachidae (f Eodromeinae), and | Liadytidae.