Ocean sediment is a 'mudtropolis'—meet the carbon-cycling creatures thriving beneath the seabed

Sitting in darkness, deep below the sunlit surface, an iridescent nightmare awaits its prey. With precision and speed, it strikes and slices a passing fish clean in half with a set of jaws twice the width of its head. The armor-plated creature retreats into its hole, quarry in tow, to rejoin the bustling metropolis of animals living in a network of burrows in the mud.