A new genus and species, Platylampona mazeppa, are described for an unusual, newly discovered ground spider from Queensland and northern New South Wales. Although the body of these animals is greatly flattened, as is characteristic of both trochanteriids and hemicloeine gnaphosids, the new genus belongs to neither of those groups but rather to the subfamily Lamponinae, and thus represents a third lineage of Australian gnaphosoids that has acquired a greatly flattened habitus.