Trocharea Etallon, 1864

Vasseur, Raphaël & Lathuilière, Bernard, 2021, Pliensbachian corals from the Western Tethys, Geodiversitas 43 (22), pp. 1187-1291 : 1206

Genus Trocharea Etallon in Thurmann & Etallon, 1864

SPECIES ORIGINALLY INCLUDED. — Trocharea actiniformis Etallon in Thurmann & Etallon, 1864.

TYPE SPECIES. — Trocharea actiniformis Etallon in Thurmann & Etallon, 1864 ( Thurmann & Etallon 1864: 411, pl. 58, fig. 4), by monotypy.

REMARKS

The nature of the relationship between Trocharea and Trochoplegma Gregory, 1900 is a question which is not completely resolved. One important reason is that the type material of Trocharaea ( T. actiniformis Etallon, 1864 ) is lost. For Trochoplegma the type material is housed in Calcutta and has not been revised but we have some ideas of the genus on the basis of topotypes studied by Beauvais (1978) or by Pandey & Fürsich (1993). Alloiteau (1957) and Fischer (1969) remarked that Trochoplegma differs from Trocharea by its tendency of compactness in septa of first order. They very probably did not see the type material or even topotypes and we cannot confirm their criteria. On the basis of topotypes of Trochoplegma tenuilamellosa Gregory, 1900 , the type species of the genus, Beauvais (1978) distinguished the genera with help of two characters: the wall and the epitheca. In Trochoplegma the wall would be absent and the epitheca present, when in Trocharea the wall would be a synapticulotheca and the epitheca would be absent. We are not certain to be able to differentiate the two character states especially when the notion of pennular envelope ( Gill 1967) was not taken into account. Pandey & Fürsich (1993) maintained the distinction between the genera Trochoplegma and Trocharea underlining the tendency to become colonial in Trochoplegma . In fact they maintained the two genera because the species are quite distinct in the Bathonian of Kachchh. We are not certain of the independence of these genera and we note that several german authors have put the type species of Trochoplegma or other species of the same genus within the genus Trocharea (see Geyer 1955; Flügel 1966; Nose 1995; Nose & Leinfelder 1997). The smaller size of trabeculae in Trochoplegma , the slightly dipping outward meniana, the exsert character of septa, the tendency toward intracalicular budding, the wavy aspect of septa in distal view are other possible criteria but it seems that all these characters do not always vary together in the same direction (mosaic variation) and could correspond to a variation at the scale of species.

Chomatoseris Thomas, 1935 is free living and shows a downward growth, Trochoplegmopsis Roniewicz, 1976 has subcompact septa and has a papillose columella.