Boreskov

PP‐63for almost all discs. Radial units look like fine straight bands along the fossils; they aresometimes combined and spread out to form root‐like appendages. Concentric unitsresemble thin or wide strips bounded by fine circular bands; elastic membranes whichseparated the adjacent areas of different pressure seem to be the structural element in thiscase. It is clear that a configuration of the attachment disc depends on the disposition ofstructural units and on the type of the growth. For example, if the concentric membranesdominate the construction the attachment becomes similar to disc more or less flattened;the prevailing radial units, on the other hand, look like root‐like outgrowths (A. Seilacher(2001) described the two similar morphospaces of concretions such as Liesegang rings anddendrites). Besides of the two morphospaces, quite a number of intermediate forms may beexpected. What can we see in fossils? There are common and easily diagnosed morphotypesof Vendian attachment structures: discoidal cyclic forms; flattened forms (e.g. Ediacaria);conical forms with radial outgrowths arranged both in chaotic (e.g. Hiemalora from Siberia)and in regular cyclic (e.g. Eoporpita) patterns; composite forms exhibiting a combination ofsome features of the above three morphotypes (e.g. Palaeophragmodictya and others)(Serezhnikova, 2007, 2010). These morphotypes are not restricted to certain systematicgroups, but rather ethological and ecological categories ― that is, they reflect differentmanners of attachment to or within the substrate. Let's place some morphotypes ofattachments in the matrix with the discoidal forms along the horizontal axis and radial formsalong the vertical one. It is two lines of "pure" forms. The arrangement of the objects shouldbe in hierarchical order, for example, an object of the lower level can be transformed intothe higher level etc. So the following pattern is expected in the line of radial forms: smalldiscs with outgrowths lying in the plane, with outgrowths going through the sediment andspreading out and eventually branching out. The line of discoidal begins from irregularconcentric forms and then ascends to regular zonal ones. Such a pattern for cyclic forms issuggested by M.A. Fedonkin (1985) and Yu.A. Gureev (1987). The members of mean matrixpoints can be selected according to basic features of some attachment discs.As a result of these simple operations, we have a table (matrix) with a number of cellsarranged hierarchically. According to the data table, the most simple and uniform discs occurin the late Neoproterozoic sediments of Newfoundland, Canada, the "middle" forms arefrom the Yudomian of Arctic Siberia and the most complex attachment discs occur in thefossil assemblages from the Ediacaran of Australia and from the Vendian of the White Sea.245