Velvet Worms, Hamburg, Germany

Photograph by O. Louis Mazzatenta

These intertwined velvet worms, or onychophorans, are living fossils, holdovers of the Cambrian explosion of life-forms that occurred about 530 million years ago. Velvet worms became land dwellers some 250 million years ago but survive today only in dark, moist habitats such as the leaf litter in Costa Rican forests. These worms were photographed at the University of Hamburg in Hamburg, Germany.

(Photo shot on assignment for "Explosion of Life: The Cambrian Period," October 1993, National Geographic magazine)