Cambrian Microfossils of the Genus Corollasphaeridium: New Interpretation and Revision of Systematics

Abstract

Bell-shaped microfossils found in Lower Cambrian Tommotian of the Siberian Platform were compared with morphologically similar forms of the Lower Cambrian of Australia, assigned to the acritarch genus Corollasphaeridium (Martin in Dean et Martin, 1982) Martin, 1992 (Gravestock et al., 2001). Revision of the genus using geometric-morphometric method allowed us to justify the separation of Siberian and Australian forms into a separate genus Spicaticampaniformis gen. nov. with two species in its composition. A description of the new genus is given and supplemented descriptions of species of S. aliquolumus and S. opimolumus. According to the revealed characteristics of their structure, excluding the form of a whole closed body, inherent to acritarchs, and taking into account the variability of features comparable with model organisms (priapulids, acanthocephalans, chitinozoa), the assignment of the genera Corollasphaeridium and Spicaticaticampaniformis to the Metazoa group is proposed. General regularities in the variation of species of Spicaticampaniformis opimolumus and Acanthocephala, which may indicate similar ecomorphotypes, as well as Corollasphaeridium wilcoxianum and Priapulida, which may also be ecomorphotypes, are described.