New Ediacaran fossils from the Ukraine, some with a putative tunicate relationship

Abstract

Sack-like body fossils Finkoella ukrainica gen. et sp. nov. and F. oblonga sp. nov., and reticulate fossil Pharyngomorpha reticulata gen. et sp. nov. are described from the upper Ediacaran shallow-marine deposits of Ukraine, which are no younger than 557 Ma. The first two resemble the flattened bodies of tunicates showing mainly the outline of tunica, while the third is considered as a fragment of the pharyngeal basket of a tunicate. F. ukrainica is represented by smaller individuals interpreted as juveniles, which may occur in clusters together with less numerous larger individuals. The larger forms are interpreted as adults, some of which show the preserved oral/atrial syphons and possible traces of internal organs bulging through the tunica. Moreover, Burykhia sp. from the uppermost Ediacaran of the same region is presented. This is the second and younger occurrence of the genus Burykhia, which is preserved as a possible fragment of the pharyngeal basket. All the fossils are preserved as the “death masks” between microbial mats, and their appearance depends partly on the relation to the parting surface on which they are observed. The presented new taxa along with the literature data reinforce the possibility that tunicates originated already in late Ediacaran.