Dimorphosmilia
Tomes 1901, p. 78
Dimorphosmilia Tomes 1901, p. 78 is a junior synonym (available and invalid), see Gonioseris Duncan, 1872, p. 21.
Dimorphosmilia is considered as the developed astogenic stage of Gonioseris. Consequently, in terms of nomenclature, we consider Dimorphosmilia Tomes 1901 as a junior synonym of Gonioseris Duncan 1872.
Type Species
Dimorphosmilia eboracensis Tomes 1901, p. 79, pl. 20 fig. 1-4; Monotypy
Type Specimen: Syntype; NHMUK R 11312-11314 and 11317 to 11336; Verified; Dry Preserved
Type Locality: Millepore bed of the inferior Oolite (Bajocian) of Claughton Wyke, Great Britain
The type-species was never cited since Tomes 1901. There are 24 syntypes. R 11312 would be a nice lectotype. The samples were erroneously registered as Dimorphastraea in the collections. The example figured by Tomes pl. 20 fig.1-4 is the only one showing a symmetry 8 and is probably this that has been polished (R 11323)
Classification
Description
The description given thereafter is the description of the colonial stage (see Gonioseris for the younger ontogenic stages). Colonial meandroid corallum with short radial valleys and elevated collines arranged according to a hexagonal or pentagonal plan around a central mouth. Epitheca fully or partially covering costae. Radial elements are compact free, unequal, straight or slightly curved costosepta. Lateral faces ornamented with opposite carinae. No pali. Microstructure unknown but the ornamentation of septa suggest a montlivaltid microstructure. Endotheca present with dissepiments. Central zone of corallites occupied by a wide fossa, synapticulae absent, The wall common to the colony is an intercostal paratheca covered by an epitheca. It is by no mean homologous to the wall between valleys issued from S1 of the young stage.
Remarks
There are some lines of evidence to admit Gonioseris as a young stage of Dimorphosmilia. 1. They come both from the same outcrop (Cloughton Wyke) and up to now from nowhere else. 2. S1 from Gonioseris, already remarked for their strange angular anastomoses, become walls between valleys in Dimorphosmilia. 3. As already established by Duncan (1872) for Gonioseris and by Tomes (1901) for Dimorphosmilia both show symmetry 5 and 6 when symmetry 5 is exceptional in Scleractinia. 4. The dimensions of corallum are compatible. 5. The other dimensions are compatible. 6. The Montlivaltid structure of septa is also shared between both genera. 7. The difference in the lower surface can be explained. The costae of Gonioseris with their nice anastomosing pattern are still present in Dimorphosmilia but fully or partially covered by an epitheca. Both show the lower concavity. This suggest that the mobility was probably possible in the young stage but certainly less efficient in the "adult" stage. One nominal species is known
Distribution
- Western Europe; Middle Jurassic
This page has been in preparation since 18-Aug-2009 16:42
This version was contributed by Bernard Lathuilière on 09-Mar-2013 08:35.
Page authors are: Bernard Lathuilière. Please contact the editor if you would like to contribute to the diagnosis of this taxon.
The editor is: Bernard Lathuilière
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