Sideroseris Wells, 1945

Baron-Szabo, Rosemarie C., 2008, Dendrophylliina, Caryophylliina, Fungiina, Microsolenina, and Stylinina, Zootaxa 1952, pp. 1-244 : 158

Genus Sideroseris Wells, 1945

(= Rhabdophylliopsis Alloiteau & Tissier, 1958 , Type species. Rhabdophyllia tenuis Alloiteau & Tissier, 1958 [non Reuss, 1868] = Rhabdophylliopsis alloiteaui Barta-Calmus, 1973 , Danian of France).

Type species. Sideroseris durhami Wells, 1945 , Eocene of Barbados .

Diagnosis. Solitary, subcylindrical to trochoid (corallite diameter to around 10 mm) and colonial, arranged in phaceloid clumps. Solitary stage probably with a corallite height to 10 mm. Costosepta thin, compact, strongly granulated laterally. Columella papillose, made of a small number of trabecular rods. Synapticulae mainly peripherally. Dissepiments absent. Wall synapticulothecal, perforate.

Remarks. Wells (1945) created the genus Sideroseris using a single corallum that was conical in shape. Later, in Middle Eocene sediments from Mexico, Frost & Langenheim (1974) discovered phaceloid clumps produced by polyps that were identical with Sideroseris in every skeletal structure except for the type of polyp integration. The same observation was made by Baron-Szabo et al. (2004) studying material form Danian sediments of Argentina. In addition, numerous individual polyps were found together with the phaceloid clumps. Moreover, specimens that were in the early stages of producing additional polyps by extracalicinal budding occurred frequently (Baron-Szabo, unpublished data). Generally, early budding stages were found in corallites that were at least around 10 mm in height. While the presence or absence of colonial development in scleractinians represents a very important generic feature, there is a small number of scleractinian genera that seem to be able to occur in both forms: These taxa exist as solitary forms up to a certain ontogenetical stage after which they develop into a colonial form. This feature has been observed for, e.g., Trachyphyllia Milne Edwards & Haime (Baron-Szabo 2006) and also applies to additional forms like Syzygophyllia Reuss (Baron- Szabo unpublished data, Sanders & Baron-Szabo in prep.), whereas in phaceloid forms like Cladocora Ehrenberg , Calamophylliopsis Alloiteau , Dermosmilia Koby , Cladophyllia Milne Edwards & Haime , Carolastraea Eliášová , and many others, such “solitary” feature has never been observed, indicating that in genera of the latter type the first gemmation takes place at a very early ontogenetical stage without regard to the budding frequency at later stages. For example, in several species of Calamophylliopsis (compare Turnšek 1972), Cladophyllia (e.g., Baron-Szabo 2002, 2006), Carolastraea (e.g., Eliášová 1976) and others, long corallites are present that rarely branch (e.g. in the holotype of Cladophyllia dichotoma [ Goldfuss 1826] branches are often up to 6 cm without budding), however, no forms have been reported that could be interpreted as solitary forms of any of these taxa. On the contrary, pieces of them were always identified as fragments of a colony.