Petalonamae

For similar fossils, see Ediacaran biota.

Petalonamae Temporal range: Ediacaran-Cambrian
File:Charniodiscus arboreus (TMP 1993.140.0001), Royal Tyrrell Museum, Drumheller, Alberta, 2025-07-13.jpg
Arborea arborea
Scientific classification Edit this classification
Kingdom:	Animalia
Phylum:	†Petalonamae Pflug, 1972
Subtaxa
†Rangeomorpha †Erniettomorpha †Arboreomorpha incertae sedis †Ramellina †Stromatoveris †Thaumaptilon †Zolotytsia †Gigarimaneta †Petalostroma? †Parviscopa? (possible juvenile Primocandelabrum)
Synonyms
Frondomorpha

The petalonamids (Petalonamae) or frondomorphs are an extinct group of archaic animals typical of the Ediacaran biota, dating from approximately 635 million years ago to 516 million years ago. They are benthic and immobile animals, shaped like leaves, fronds (frondomorphic), feathers, or spindles. While initially considered algae or octocorals akin to 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.

Generally, these animals possess bilateral symmetry, like a feather with one axis and two sides. Some may be trilateral, with one axis and three sides, as seen in the most basal forms; the erniettomorphs. Phylogenetically they are particularly difficult to classify. Lacking mouths, intestines, reproductive organs, or any other preserved evidence of internal structures, the morphology of these animals is very strange by current standards. The most widely accepted hypothesis is that they could directly absorb nutrients from the water around them by osmosis. It is commonly conjectured that these organisms were fluffy at least in appearance, as if "inflatable." The fronds were composed of branched, tubular structures, and the organism was anchored to the substrate by a bulbous structure akin to a holdfast.

Distribution

Ediacaran of Canada, Namibia and Russia.

Phylogeny

The below phylogeny follows Hoyal Cuthill & Han (2018) who recover a clade which they name Petalonamae, including representatives of Rangeomorpha, Arboreomorpha and Erniettomorpha, Stromatoveris from the Lower Cambrian, as well as Dickinsonia, and identifying them as animals.

Animalia

Placozoa File:Trichoplax adhaerens photograph (no background).png Porifera File:Callyspongiatransparent.png †Petalonamae †Rangea File:Rangea scheiderhoehni 1.jpg †Stromatoveris File:Stromatoveris psygmoglena.jpg †Pteridinium File:Pteridinium simplex.jpg †Ernietta File:Ernietta plateauensis 1.jpg †Arborea File:Charniodiscus arboreus (TMP 1993.140.0001), Royal Tyrrell Museum, Drumheller, Alberta, 2025-07-13.jpg †Pambikalbae File:Pambikalbae hasenohrae.jpg †Swartpuntia File:Swartpuntiagermsi.png †Dickinsonia File:Dickinsonia costata.jpg Eumetazoa File:Mnemiopsis leidyi 247259012.png File:Jellyfish, Shaw Ocean Discovery Centre (7201323966).png File:Saccoglossus kowalevskii by Spengel 1893.png

See also

• †Vendobionta
  • †Trilobozoa, another group of Edicaran animals who have trilateral symmetry, similar to basal petalonams.
  • †Proarticulata, another group of enigmatic Ediacaran animals
• Eumetazoa