The Cambrian Explosion: Opabinia
Some of the animals of the Cambrian explosion have no living descendants.
They represent phyla which are extinct. In the painting on the left, Opabinia
is shown pulling a bristle worm out of the substrate. Opabinia is depicted
alone on the right. It has five eyes and a very strange frontal appendage.
No creatures today share this odd body plan.
Among the implications of the Cambrian explosion is that overall diversity
at the level of phyla has decreased since the Cambrian. Our idea of an evolutionary
tree starting from a single trunk and bearing many branches, should be changed
to a shrub which has suffered a lot of winterkill. Many early branches are
dead, but the remaining branches are bristly with new growth.
Detail of painting by D.W. Miller from American Scientist, March-April, 1997. Labels added