Pathological Changes of Archaeocyathids

Abstract

One of the unique groups of skeletal organisms of the lower Cambrian is the archaeocyathids, a group restricted to the early Cambrian and showing stages of their evolution. A longitudinal section through an archaeocyathid can show ontogenetic stages from a juvenile cup to the complete development of species characters. This feature allows the study of ontogenetic changes in the group, revealing various heterochronies and other patterns that can be directly linked to evolutionary reconstructions. Archaeocyaths from various regions include a large number of damaged and deformed cups. It is shown that deformations and pathological changes originating in the Tommotian (Nochoroicyathus sunnaginicus Zone) could be manifested in the general evolution of the group.