Some of the earliest bilaterians were wormlike, and a bilaterian body can be conceptualized as a … Se mere

The hypothetical most recent common ancestor of all bilateria is termed the "Urbilaterian". The nature of the first bilaterian is a matter of debate. One side suggests that acoelomates gave rise to the other group… Se mere

The first evidence of bilateria in the fossil record comes from trace fossils in Ediacaran sediments, and the first bona fide bilaterian fossil is Kimberella, dating to 555 million years ago. Earlier fossils are controversial… Se mere

The Bilateria has traditionally been divided into two main lineages or superphyla. The deuterostomes traditionally include the echinoderms, hemichordates, chordates, and the extinct Vetulicolia. The protostomes include mos… Se mere

• Embryological origins of the mouth and anus Se mere

• Tree of Life web project — Bilateria
• University of California Museum of Paleontology — Systematics of the Metazoa Se mere