A few years ago I wrote a couple articles for Cryptid Culture magazine. While the publication itself seems to have gone under, you can still order copies of it on their website. Definitely go check it out. There are lots of great articles and illustrations. Here I'd like to share one of the articles I wrote on a most unusual deep-sea cryptid which may have existed since before the dinosaurs.
PALEODICTYON
It’s often said that the deep sea is as mysterious and
unexplored as the distant gulfs of space. There is much truth in this, for new
and strange species are constantly being discovered in the unlit abyss. Even
those scant few creatures which have been seen by surface-dwellers may be
little more than ghosts: brief flickers in a submersible’s lights, enigmatic
shapes glimpsed for but a second on an ROV camera, strange carcasses damaged
almost beyond recognition by the rough journey to the surface in a fisherman’s
net. And in some cases, these phantoms may only be known indirectly from the
marks of their passage left in the environment.
In 1976 oceanographer Peter A. Rona was using an underwater
camera towed behind a research boat to explore the seafloor along the
Galapagos Rift, a volcanic hotspot in the Pacific Ocean near the islands made
famous by Charles Darwin. Though the Rift is dotted with numerous hydrothermal
vents that are abundant with life, the area Dr. Rona was exploring was far
away from the hot, black-smoking chimneys. It was little more than an undersea
desert- a flat expanse of mud and silt almost devoid of life. So it was a great
surprise when the camera came across a hill of sediment about the size of a
silver dollar covered with an intricate pattern of holes. The placement of the
holes was so geometrically perfect, and the find itself so out of place, that
Dr. Rona at first assumed that the other researchers on the exploration team
had somehow played a trick on him. But they were just as surprised as he was by
the find.
Later excavations of the holes revealed that they led to
shafts that connected to a network of honeycomb-like interconnected tunnels
about an inch below the surface. A burrow of some sort. A burrow so geometrically perfect as to
almost seem made by intelligent beings- though there is no need to invoke an
intelligent builder here since many animals can create startlingly precise
structures.
The first question Dr. Rona and the others asked, of course,
was just what animal had made these remarkable structures. No living organisms
were discovered when the burrows were dug up. There weren’t even any telltale
food scraps, bits of DNA, or other detritus to provide a clue to the identity
of these deep-sea engineers.
The mystery only grew deeper as word of the discovery spread.
A few years after Dr. Rona formally described the strange structures, he was
contacted by paleontologist Adolf Seilacher, who showed him fossil burrows
that were nearly identical to the Galapagos Ridge hills. Seilacher’s fossils,
dubbed Paleodictyon (trace fossils
such as burrows, footprints, and coprolites are given their own distinct scientific
names), dated from the Eocene Epoch, approximately 55 million years ago. Other,
simpler but still very similar fossil burrows dated all the way back to the
early Cambrian Epoch, when large multicellular animals first appeared in the
fossil record. Whatever was making the mystery
burrows had apparently existed on Earth with minimal evolutionary change since
before the dinosaurs had evolved. Or, at least, with little change in the way it
constructed its dwellings. Once this striking continuity was brought to light,
the still-unknown maker of the modern tunnels was given the name Paleodictyon nodosum.
Since the initial discovery in 1976, Doctors Rona and
Seilacher, along with other researchers, have found thousands of Paleodictyon burrows along volcanic
rifts in both the Pacific and Atlantic oceans. Like those first specimens, the
other structures were found on the barren seafloor far from the hydrothermal
vents and their diverse ecosystems. Perhaps these unknown animals have evolved
to survive in this rough environment, adapting to feast on what few nutrients are
present in the form of “marine snow”- tiny bits of organic matter formed from
bits of dead plankton and other organisms that constantly rain (or rather,
snow) down from above.
|
A large xenophyophore in its shell. |
But the question still remains: what sort of animals are
making these Paleodictyon structures,
exactly? One hypothesis is that they are
a species of giant amoebae known as xenophyophores. These single-celled
organisms can be found in the deepest parts of every ocean. Most species cement
sand and other debris together to build complex, rippled shells or “tests”
which can resemble brains, sponges, heads of lettuce, or other corrugated
objects. Some, however, are known to live buried in the sediment, admittedly in
much simpler burrows.
If Paleodictyon
nodosum is indeed a xenophyophore, though, why does it excavate such
geometrically complex burrows? Laboratory tests have shown that the convex
lens-shaped mound over a Paleodictyon
burrow draws water down through the vertical shafts, so perhaps the structure
is used to pull suspended marine snow from the water column down to the buried
amoebae. Alternatively, the tubes could be used for “farming” bacteria on their
walls, much like how leafcutter ants in the Amazon will farm fungi on the bits
of vegetation, they bring into their nests.
The farming hypothesis is suspect, though, since research has shown that
the concentration of bacteria in the tubes is no higher than the concentration
on the sea floor above, indicating that there is no deliberate cultivation occurring.
Dr. Rona’s favored possibility as to the identity of Paleodictyon is that the “burrows” may
actually be the outline casts of sediment-dwelling sponges or other soft,
filter-feeding organisms. This idea is not as strange as it may seem. Many
sponges will burrow into mud, coral, or even the hard shells of oysters (the
latter by using a weak acid secreted by the sponge’s cells) to protect their
soft bodies from predators. As to why no remains of the animals themselves have
been found, Dr. Rona suggests that they may have died and been completely
devoured by bacteria and small deep-sea scavengers, leaving behind the
geometric pit structure as the only evidence of their existence.
It is still curious, though, that in all these years of
searching not a single burrow has been found that contains a live Paleodictyon nodosum, or even a few
small scraps of their remains. Perhaps it is because the structures are
actually much older than they appear. Though the burrows seem freshly dug, the
seafloor deserts where they are found are still, quiet places lacking any
current and only rarely disturbed by other organisms. These unusual conditions may have allowed the
burrows to persist intact for hundreds of years, long after their builders had
completely rotted away.
The lack of a living builder may also simply be due to the
fact that the area where Paleodictyon
burrows are found has not been explored that extensively. Investigating the
deep sea is an expensive endeavor that requires reserving highly competitive
slots of time with a submersible or diving robot. Rona and Seilacher simply
haven’t had enough time or money to search for these enigmatic builders. Though
they have found thousands of Paleodictyon
burrows, perhaps these are only the graveyards of a long-dead colony of the
creatures. Perhaps the living animals lie just a few miles beyond the
submersible’s light, waiting for someone to finally stumble across them.
Paleodictyon has
received some media attention, though. Most notably in the form of “Volcanoes
of the Deep Sea”, an IMAX documentary chronicling the researcher’s discovery
and search for the animal.
On a final, interesting side note, the first recorded
reference to Paleodictyon fossils may
have come from Leonardo da Vinci. In the Leicester Codex, Leonardo records
extensive notes on fossilized shells and other traces of prehistoric marine
organisms. Among his drawings is a small, quick sketch of a honeycomb-like
structure. Though the sketch is unlabeled, it is not a huge stretch to
postulate that this may have been a representation of Paleodictyon, especially since these striking trace fossils are
common around the inventor’s childhood home in the valley of the Arno River.