as well: If this was the remains of the body of a creature, you would expect to find organic matter from that creature throughout the burrow. However, when the burrows were tested for DNA, scientists found DNA from different types of large protists between different burrows. This suggests that the DNA found is just there because it was transported there by currents. However, one encouraging fact is that one of the types of DNA found in a burrow was of Vanhoeffenella, which creates hexagonal burrows similar to those of P. nodosum. The barium content in the sediment making up the burrows had no significant difference from the barium content in the surrounding sediment. This is inconsistent with the burrows of other xenophyophores. Also the complexity and evenness of the burrows is not consistent with the forms that xenophyophores generally create. Fossil record The fossil record indicates that these burrow-types could be one of the earliest examples of complex structures being built by animals. Fossils of Paleodictyon nodosum were first found in the cliffs of Spain in the 1950s. Since then, they have been discovered all over Europe and in Wales. They are generally found in flysch deposits from the Eocene epoch. The oldest fossils show much less uniformly hexagonal burrows, but in higher strata (i.e. later in geological time) their burrows become much more consistent and precise. Popular exposure The IMAX film Volcanoes of the Deep Sea describes the search for Paleodictyon nodosum, using the deep-water submersible DSV Alvin near volcanic vents that lie 3,500 meters (12,000 feet) underwater in the Mid-Atlantic Ridge. Samples were taken from several honeycomb burrows, however no creatures were found in any of them. They theorized that the burrows were being used for bacterial farming by whichever creature created them. References Trace fossils