Colonies are disc shaped, free-living (lunulitiform) and attached to a minute substrate often completely enveloped. Autozooids and vibracula open onto the convex upper surface whereas the concave underside is covered by kenozooids arranged in long radial sectors. Colonies from the Coralline Crag are typically up to 7 mm in diameter, most originating asexually by regenerative growth from a fragment of a pre-existing colony. The ancestrula and early astogeny have not been described in material from the Coralline Crag.
Autozooids are rounded rhombic, longer than wide, on average about 0.43-0.55 mm long by 0.28-0.40 mm wide. Gymnocyst and spines are lacking but the granular cryptocyst is well-developed, with up to six lobate denticles extending inwards almost as far as the midline of the zooid. The opesia is arch shaped distally. Ovicells are lacking.
Vibracula are present distally of each autozooid and measure 0.20-0.23 mm long by 0.18-0.20 mm wide. They have ear-shaped opesia, asymmetrical condyles and proximally directed rostra which are deflected either to the left or right of the associated autozooid.
This species resembles Cupuladria cavernosa but can be distinguished by the lobate gymnocystal denticles extending part way across the opesia. Note that in poorly preserved specimens these structures may be eroded away, making distinction between the two species more difficult.
Pliocene, Late Zanclean–Early Piacenzian, Coralline Crag Formation, Suffolk, UK.
Reussirella haidingeri was originally described from the Miocene of the Vienna Basin, Austria and has been recorded from numerous other Neogene localities across Europe (see Baluk & Radwanski 1984 and references therein; Bishop & Hayward 1989). It is likely that future taxonomic revision will result in splitting of R. haidingeri, narrowing both its stratigraphical and geographical ranges.