When first discovered in the deep sea, based on morphological evidence, Dendrogramma could not be placed in any known animal phylum. Tantalizingly, its distinctive branching structures were similar to 560 million year-old Precambrian fossils. Upon further review, using newly collected and better preserved specimens, phylogenetic analysis revealed that Dendrogramma is actually a part of a deep sea siphonophore, related to the Portuguese Man o’ War. Each siphonophore is made up of a colony of many smaller individuals. The distinctive mushroom-shaped “bodies” are actually pieces detached from a larger colonial organism, but what the intact colony looks like is still a mystery.
David Paul and Hugh MacIntosh, Museum Victoria, Melbourne, Australia