Petalonamae
Petalonamae
Proposed extinct group of animals
The petalonamids (Petalonamae) are an extinct group of archaic animals typical of the Ediacaran biota, also called frondomorphs, dating from approximately 635 million years ago to 516 million years ago. They are benthic and motionless animals,[4] that have the shape of leaves, fronds (frondomorphic), feathers or spindles and were initially considered algae, octocorals or sea pens. It is now believed that there are no living descendants of the group, which shares a probable relation to the Ediacaran animals known as Vendozoans.
It is commonly conjectured that the organisms were fluffy at least in appearance, as if "inflatable." They are particularly difficult to classify phylogenetically. Lacking mouths, intestines, reproductive organs, and with no preserved evidence of internal structures, these organisms' existence is very strange by current standards. The most widely accepted hypothesis is that they could suck nutrients from the water around them by osmosis.[5] The fronds were composed of branched, tubular structures, and the organism was anchored to the ground by a bulbous structure.
The symmetry is generally bilateral, like a feather with one axis and two sides. It can also be trilateral, with one axis and three sides, as seen in the most basal ones, the erniettomorphs.[6][7]
