Rona, Peter A., Natural History
"Extinct" for 50 million years, an enigmatic fossil species may still live at the bottom of the sea-but it defies capture.
So little is known about the deep ocean, that those of us who explore it should expect surprises. Yet even I and my research team from the National Oceanic and Atmospheric Administration were dumbfounded in 1976, when we studied photographs of the seafloor in the middle of the Atlantic Ocean. From our research ship Discoverer, we had slowly towed a deep-sea camera on a cable two and a half miles long. Pings of sound had guided the camera roughly ten feet above the seafloor, while strobe lights fired every twenty seconds to illuminate patches about the size of a bed sheet. In those days we had to wait until we were back on land-Florida, in this case-to process the film and view the images.
At first all we saw was the silt that coats the ocean floor. Then something a little bigger than a poker chip caught our attention. Under a magnifying glass, a distinctive pattern of black dots appeared in our photograph. The dots were evenly spaced and arranged in crisscrossing rows, forming a perfect six-sided figure that resembled the center of a board of Chinese checkers [see lower photograph on page 53].
Once we knew what to look for, we recognized thousands of these hexagonal forms in our sequence of hundreds of photographs. Could such a uniform pattern be the sign of some unimagined life-form? Certain corals, for example, build structures with hexagonal symmetry, but not in seafloor sediment. Our imaginations ran wild. Was this a hoax perpetrated by the people who had processed our film? Was this some strange cargo spilled from a shipwreck? A message left by extraterrestrials? Surely my local marine biology colleagues at the University of Miami would quickly enlighten us. But they were just as puzzled as we were. They referred me to their counterparts at the National Museum of Natural History, Smithsonian Institution, in Washington.
The area we had surveyed was in the rift valley that lies along the center of the Mid-Atlantic Ridge, a mile-high undersea volcanic mountain range that traverses the Atlantic from north to south. The ridge links with similar ridges in the Arctic, Indian, and Pacific oceans [see map on page 52]. Along this global ridge system, continent-size tectonic plates, which form the outer shell of the planet, are moving apart, and new crust is constantly being created by the upwelling of magma from the Earth's hot interior. As it emerges, the molten rock cools, solidifies, and spreads apart at a rate of a few inches per year. Earthquakes accompany the slow widening of the seafloor.
Armed with a dozen black-and-white photographs, I made the rounds behind the scenes at the Smithsonian. My first consultation was with Frederick M. Bayer, an expert on corals. But Bayer concluded that the form was not a coral at all, and introduced me to an expert on another phylum of marine invertebrates. By the end of the day, specialists in every major group of marine invertebrates had examined the photographs and had drawn a blank. Their only advice was to prepare an article for publication in a scientific journal, with photographs showing the pattern as related to "an invertebrate of uncertain identity."
No sooner had the suggested article appeared, than I received a letter and a reprint of a paper from Adolf "Dolf" Seilacher, a paleontologist then at the University of Tübingen in Germany. Seilacher is an expert on classifying and interpreting traces of life-such as the trails left by worms-that are preserved in ancient marine sediments. "Your pictures were a real thrill to me," his letter began. "Hoping that you have in the meantime received my reprint, the perfect identity with the trace fossil Paleodictyon nodosum of my paper is beyond any doubt."
Seilacher's paper described a fossil form preserved at least 50 million years ago in sediments of the deep-sea floor, which were now exposed on land at various sites in continental Europe. …