Morphogenesis and taxonomic value of the circumaxial skeleton in Rugosa (Anthozoa)

Abstract

An elevated skeletal structure surrounding an empty axial area occurs in many unrelated taxa within the Rugosa. This structure, commonly termed the aulos, was first differentiated and described by Grabau in 1922. Most terms introduced by that author for individual morphotypes have not been accepted because the taxa he chose to illustrate the typical development do not correspond to his diagnoses. The morphogenetic study on some circumaxial structures in this paper points out differences in their origin, their predicted role in the physiology of the coral polyps. The study shows both the advantages and disadvantages of the use of these circumaxial structures in taxonomy. In addition to the term aulos, which was introduced by Smith in 1928, new terms i.e. circulotheca and columnotheca are here introduced for the circumaxial structures that also are newly proposed names, to allow distinguishing them from true axial structures.

On three rugose coral genera from Serpukhovian strata in the Upper Silesian Coal Basin, Poland

“…However, all major septa reach their mature, rhopaloid character. Their arch is now comparable to an incomplete circulotheca of Fedorowski (2009d). The alar septa and the left counter-lateral septum became slightly shortened and the first minor septa become visible in the corallite lumen next to the counter septum and in septal loculi of the counter quadrants adjacent to it.…”

“…The elongated counter protoseptum in Soshkineophyllum Grabau 1928(Plerophyllinae Sokolov, 1960 and Claviphyllum (Stereolasmatinae Hill, 1981 ) can serve as one example. The aulos and the columnotheca may be taken as another example; they appear very similar in general morphology and are similar in their functions, but are completely different in origin (Fedorowski 2009d). (B) According to the regulations of the International Code of Zoological Nomenclature qualitative characters have at least a generic rank.…”

Vojnovskytesidae – a new family of Mississippian Rugosa (Anthozoa)

“…The primary septa ('middle dark lines') do not meet. The circumaxial structure is completely filled with sclerenchyme closely resembling, but not completely equivalent, to aulos, as re-defined by Fedorowski (2009b). The cardinal and counter septa are equal in length to the remaining major septa and participate in a circumaxial structure, but their inner margins are not bent.…”

“…5B). That lateral contiguity of the major septa is here considered to represent a circulotheca , closely comparable to the typically developed immature circulotheca of Fedorowski (2009b, fig. 4A-C).…”

“…Not all of them are in lateral contiguity. Thus, the circulotheca as defined by Fedorowski (2009b) is incomplete. The cardinal septum remains long, approaching, but not reaching the counter septum, which is elongated and dilated axially.…”