Paleodictyon

Paleodictyon is a trace fossil, usually interpreted to be a burrow, which appears in the geologic marine record beginning in the Precambrian/Early Cambrian[1] and in modern ocean environments.

Roy Plotnick, trace fossil researcher at University of Illinois at Chicago, modeled the form as resulting from the iterative modular growth of an unknown organism.

The infaunal xenophyophore Occultammina does bear some physical resemblance to Paleodictyon and the abyssal habitat of modern xenophyophores is indeed similar to the inferred paleoenvironment where fossil graphoglyptids are found; however, the large size (up to 0.5 m) and regularity of many graphoglyptids as well as the apparent absence of collected sediment particles (known as xenophyae) in their fossils casts doubt on the possibility.

[13] Modern examples of Paleodictyon have been discovered; however, examination failed to reveal stercomares, a hardened test, protoplasm, or xenophyophore DNA.

[14] The IMAX film Volcanoes of the Deep Sea describes the search for a living animal that produces the Paleodictyon, using the deep-water submersible DSV Alvin near volcanic vents that lie 3,500 metres (11,500 ft) underwater in the Mid-Atlantic Ridge.

Paleodictyon minimum .
Paleodictyon from Miocene of Fiume Savio
The xenophyophore Occultammina has been suggested as a possible identity for the maker of Paleodictyon , but this remains controversial.