ested the Ediacaran sees animals usurping giant protists as the dominant life form. The modern xenophyophores are giant single-celled protozoans found throughout the world's oceans, largely on the abyssal plain. A recent genetic study suggested that the xenophyophores are a specialised group of Foraminifera. There are approximately 42 recognised species in 13 genera and 2 orders; one of which, Syringammina fragilissima, is among the largest known protozoans at up to 20 centimetres in diameter. New phylum Seilacher has suggested that the Ediacaran organisms represented a unique and extinct grouping of related forms descended from a common ancestor (clade) and created the kingdom Vendozoa, named after the now-obsolete Vendian era. He later excluded fossils identified as metazoans and relaunched the phylum "Vendobionta". He described the Vendobionta as quilted cnidarians lacking stinging cells. This absence precludes the current cnidarian method o f feeding, so Seilacher suggested that the organisms may have survived by symbiosis with photosynthetic or chemoautotrophic organisms. Mark McMenamin saw such feeding strategies as characteristic for the entire biota, and referred to the marine biota of this period as a "Garden of Ediacara". Lichen hypothesis Thin sections and substrates of a variety of Ediacaran fossils A modern lichen, Hypogymnia Greg Retallack's hypothesis that Ediacaran organisms were lichens has been controversial. He argues that the fossils are not as squashed as known fossil jellyfish, and their relief is closer to compressed woody branches whose compa