Turbicellepora coronopus (Wood, 1844)
Colonies are ramose, with thick branches (up to 4 mm diameter in the lectotype), or form small nodular encrustations, and comprise multiple, irregularly arranged, frontally budded zooids. The ancestrula and early astogenetic stages seemingly have not been described.
Autozooids are ovoidal in frontal outline, 0.6-0.7 mm long by 0.4-0.5 mm wide (fide Hayward 1978, p. 575), overgrown to varying degrees by new buds on the colony surface. The frontal shield is cryptocystal, strongly convex, smooth and fringed by small areolar pores but imperforate centrally. The orifice has a deep V-shaped sinus, occupying slightly less than one-third of total orifice length, and is about 0.10 mm in both length and width. Oral spines and other spinose processes are lacking. Seldom preserved in fossils, ovicells are globular, with the ectooecium perforated by up to a dozen scattered pores (fide Hayward 1978).
An adventitious avicularium occurs suborally, typically lateral to the sinus. This is often abraded, exposing the large avicularian chamber on the frontal shield of the autozooid. The rostrum is semielliptical or triangular, often inclined, and is oriented more or less laterally with respect to the axis of the autozooid. The cross bar is calcified. Larger interzooidal avicularia occur scattered among the autozooids. These are broadly spatulate, with a deep, shelf-like palate and a calcified cross bar containing a slender outgrowth (columella). The drop-shaped rostrum is 0.3-0.5 mm long (fide Hayward 1978).
The type species of the widely distributed extant genus Turbicellepora Ryland, 1963, T. coronopus was redescribed by Hayward (1978) in his revision of European species of this genus. The shape of the orifice and the interzooidal avicularia, plus the smooth calcification of the frontal shield and low suboral avicularia, allow this species to be distinguished (with some difficulty) from its congeners.
Fossil examples of celleporids such as Turbicellepora coronopus provide a major challenge in identification. This is not only due to the chaotic arrangement of the frontally budded zooids, but also difficulty in finding adequately preserved taxonomic features, notably the delicate ovicell (which is very seldom preserved intact on the colony surface of fossils) and the autozooidal orifice (which may be difficult to distinguish from other ‘holes’ and can be obscured by sediment or cement).
Pliocene, Late Zanclean–Early Piacenzian, Coralline Crag Formation, Suffolk, UK.
Also recorded by Lagaaij (1952, p. 137) as a fossil from the Low Countries (see also Bishop 1987, p. 25), and by Hayward (1978) from the Recent of the Mediterranean and the coast of northwestern Africa.