From Regeneration to Coloniality: Multiple Buds in the Solitary Coral Bothrophyllum conicum Trautschold, 1879 (Rugosa) in the Carboniferous of the Moscow Basin

Bothrophyllum conicum displays three known types of regeneration. The damaged zone is rebuilt during epimorphosis, as observed in cases of healing. Compensatory regeneration, typical for many groups of corals, is expressed in the restoration of the diameter of corallites and the typical arrangement of septa after reduction of diameter and “rejuvenation” of the arrangement of septa. Morphallaxis is the most morphogenetically complex process, in which the development of one or several buds on the maternal corallite from the residues of tissues of a damaged corallite is possible. The reorganization of the damaged tissue during morphallaxis is similar to asexual reproduction in the arrangement of newly formed septa, which are positioned like buds relative to the skeletal elements of the maternal corallite. If the maternal corallite dies, forming multiple buds, the space between the buds continues to develop and grow, forming a kind of connective tissue around the bud corallites, with a large number of skeletal elements. Probably, this tissue of the maternal organism between the buds is a source of material for the newly formed buds, similar to the coenosarc in colonial corals. The location of the plane of symmetry passing through the main and opposite septum of the buds usually coincides with the direction of the most pronounced septum of the maternal corallite that underlies the bud. Sometimes, with no dominant septa at the base of the buds, the plane of symmetry is perpendicular to the maternal septa.