What is the First Bilateral Animal?
The first body fossil of a bilateral animal is Vernanimalcula (“small spring animal”), a simple metazoan that lived between 580 and 600 million years ago, during the Ediacaran period. Vernanimalcula was discovered in 2005 in a phosphatic fossil deposit in Guizhou Province, China, called the Doushantuo Formation. Phosphatic fossils are extremely detailed, with features on the microscopic level, permitting analyses impossible with other fossil types. A minority of scientists argue that Vernanimalcula is a taphonomic artifact, caused by the intrusion of phosphate into an inorganic or unicellular spherical object, but the majority consider it a genuine fossil of a bilateral animal. Most animals are bilateral, meaning they are symmetric around a central axis. Exceptions include the sponges, which have no symmetry, the cnidarians (jellyfish and relatives), which have radial symmetry, and a few echinoderms (starfish and relatives) with have pentaradial symmetry, but evolved from bilateral anc
