Halicephalobus mephisto

Species of roundworm

Halicephalobus mephisto is a species of nematode, among a number of other roundworms, discovered by geoscientists Gaetan Borgonie and Tullis Onstott in 2011. It was detected in ore recovered from deep rock fracture water in several gold mines in South Africa 0.9 km (0.56 mi), 1.3 km (0.81 mi), and 3.6 km (2.2 mi) under the surface of the Earth. Onstott said that "it scared the life out of me when I first saw them moving", and explained that "they look like black little swirly things". The finding is significant because no other multicellular organism had ever been detected farther than 2 km (1.2 mi) below the Earth's surface.

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