Palaeophragmodictya spinosa sp nov., a bilateral benthic organism from the Vendian of the Southeastern White Sea region

A fossil organism, Palaeophragmodictya Gehling et Rigby, 1996, previously classified within sponges, is found for the first time in the Vendian of the Arkhangelsk Region. Based on the new finds, Palaeophragmodictya is interpreted as an attachment disc of a problematic animal with combined coelenterate and sponge morphology. Typical and unique preservational forms from the same bedding plane are described. Three-dimensional fossils are preserved as flat impressions at random horizontal levels. Bilateral symmetry discovered in the ontogeny of Palaeophragmodictya spinosa sp. nov. supports the hypothesis of initial bilaterality of Cnidaria.