Plagioecia zatoni was named by Gordon and Taylor (2015) [Colony encrusting, multilamellar, comprising a stack of discoidal, partly overgrowing subcolonies (four in both the holotype and paratype), new subcolonies originating from centre of underlying subcolony; growing edges exposing 2-3 generations of zooidal buds; colony surface crossed by ridge-like transverse growth bands. Autozooids moderately elongate, 225-338 mm long by 113-138 mm wide; apertures closely spaced, becoming more crowded towards perimeter of subcolonies, arranged quincuncially, subcircular or longitudinally elongate, 75-125 mm long by 75-88 mm wide, some closed by pseudoporous terminal diaphragms; preserved peristomes low. Gonozooid transversely elongate, crescentic or banana-shaped, 479 mm long by 1458 mm wide, lacking the roof and ooeciopore in the only non-overgrown example (Fig. 6D).]. It is not extant. Its type specimen is IGNS BZ243. Its type locality is Tumaio Limestone, Chatham Island, which is in an Eocene transition zone/lower shoreface tuff in New Zealand.