Trochocyathus Milne Edwards & Haime, 1848

Baron-Szabo, Rosemarie C., 2008, Dendrophylliina, Caryophylliina, Fungiina, Microsolenina, and Stylinina, Zootaxa 1952, pp. 1-244 : 55

Genus Trochocyathus Milne Edwards & Haime, 1848

(= Protrochocyathus Alloiteau, 1958 , Type species. Protrochocyathus madagascariensis Alloiteau, 1958 , Albian of Madagascar);

(= Paratrochocyathus Alloiteau, 1958 , Type species. Paratrochocyathus collignoni Alloiteau, 1958 , Albian of Madagascar);

(= Cyrtocyathus Alloiteau, 1958 , Type species. Cyrtocyathus collignoni Alloiteau, 1958 , Maastrichtian of Madagascar);

(= Elasmosmilia M. Beauvais, 1961 , Type species. Elasmosmilia padernensis M. Beauvais, 1961 , Upper Santonian of France);

(= Tethocyathus Kühn, 1933 , Type species. Thecocyathus microphyllus Reuss, 1871 , Tortonian of Austria).

Type species. Turbinolia mitrata Goldfuss, 1826 , Upper Cretaceous of Germany (Aachen) (see Milne Edwards & Haime 1848c).

Diagnosis. Solitary, variably conical, often turbinate to ceratoid, or discoidal, fixed or free. Costosepta compact, finely granulated laterally. Pali or paliform lobes in 2 crowns opposite all but last cycle. Columella fascicular or spongy. Wall septothecal. Endothecal dissepiments vesicular. Epithecal wall absent or present.

Remarks. The genus Trochocyathus has long been considered as lacking an epithecal wall. Re-examination of the type material of this genus, which consists of two syntypes, showed that, in general, an epithecal wall is not present (in the syntype figured in Baron-Szabo 2002, pl. 118, fig. 1, no epithecal wall seems to be present), but in the lower part of one of the two syntypes (the one figured in Baron-Szabo 2002, pl. 118, fig. 2) short strips of incomplete epithecal rings were observed. These short structures can be found only in a very few places, but they are wall developments sitting on top of the costae, which excludes them from being parts of the septothecal developments in this genus. Therefore, the generic diagnosis of Trochocyathus was emended here in adding the statement “Epithecal wall absent or present” to the generic diagnosis.

The genus Tethocyathus Kühn, 1933 , had been distinguished from Trochocyathus by the presence of both a narrow edge zone and an extensive epitheca ( Wells 1956) . Because the development of an epithecal wall is dependent on the presence of a narrow edge zone (pers. comm. S. Cairns 2008), it first of all means that the two genera are actually only distinguished by a single characteristic (=presence of a narrow edge zone). In addition, while it seems questionable whether the feature of a wide or narrow edge zone could be used to separate genera (pers. comm. S. Cairns 2008), this distinguishing characteristic (= “epithecal wall absent in Trochocyathus but present in Tethocyathus ”) does not exist because the presence of an epithecal wall in Trochocyathus was observed (see remarks above).

Subgenus. Platycyathus Fromentel, 1862 (Type species. Trochocyathus terquemi Milne Edwards & Haime, 1857 , Lower Santonian of France): like Trochocyathus but corallum discoidal, free.