A 5-meter-wide chunk of carbonate minerals embedded in a seaside cliff in northern New Zealand has yielded fossils of a shelled microorganism that may have thrived only around the small, isolated, and far-flung sites where hydrocarbons such as methane or natural asphalt seep through the ocean floor, researchers say. Although the lump is a few meters above sea level today, analyses suggest that about 20 million years ago, the minerals formed at a seafloor site, then between 600 and 2000 meters deep, where methane seeped up through the ocean bottom. Most creatures inhabiting such seeps, including microscopic ones, also live in nearby waters. But at this site, more than 95% of the foraminifera, or shelled amoebas, entombed in the carbonates were Amphimorphinella butonensis, a species now apparently extinct that has been found at only one other site—a small, asphalt-infused patch of limestone in central Indonesia. The presence of this rare species at a second site associated with deep-sea hydrocarbon seeps suggests that the creatures were specifically adapted to live in the unusual environmental conditions at such sites—the first such species to be limited to such ecosystems, the researchers reported online May in Geology.
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