''Palaeophragmodictya'' is an extinct genus of sponge-grade organisms from the

Ediacaran Period The Ediacaran ( ) is a geological period of the Neoproterozoic Era that spans 96 million years from the end of the Cryogenian Period at 635 Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last period of the Proterozoic Eo ...

. Originally interpreted as a

hexactinellid Hexactinellid sponges are sponges with a skeleton made of four- and/or six-pointed siliceous spicules, often referred to as glass sponges. They are usually classified along with other sponges in the phylum Porifera, but some researchers consid ...

sponge, the organism also bears some

coelomate The coelom (or celom) is the main body cavity in many animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it ...

characteristics, including

bilateral symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, the face of a human being has a plane of symme ...

Morphology

The organisms take the form of a rounded, dome-like bag, 7–68 mm in diameter, with an uneven margin. Radial grooves define sac-like compartments within the bag. The radial pattern has an element of bilateral symmetry. A stalk emerges from the central point of some specimens, at the top of the organism; in life, it probably extended into the water column. Ray-like filaments radiate outwards from the edge of the bag. Some structures in the organism have been interpreted as spicules.

Ecology

The organisms have been interpreted as tall suspension feeders, reaching 10 cm or more up into the sea water above them.

Original description

The genus was originally considered to be a member of the Dictyospongiidae family (hexactinellia), and was among the first Precambrian sponges to be described.

Distribution

First found in the Pound group of Australia, fossils have also been recovered from the

White Sea The White Sea (; Karelian language, Karelian and ; ) is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is surrounded by Karelia to the west, the Kola Peninsula to the north, and the Kanin Peninsula to the nort ...

region of Russia.

Other sponge-like Ediacaran animals

*'' Fedomia'' *''

Vaveliksia ''Vaveliksia'' is an extinct genus of Ediacaran Sponge-like organism with a long, tubular-shaped body and a attachment disk similar to that of Petalonamids. The ''Vaveliksia'' genus contained two species, ''Vaveliksia velikanovi'' (which hono ...

'' *''

Helicolocellus ''Helicolocellus cantori'' is an extinct sponge from the late Ediacaran, found in the Dengying Formation of South China and possibly related to the Hexactinellida. If confirmed, ''H.cantori'' would be the oldest crown group sponge known as of 2 ...

'' *''

Arimasia ''Arimasia germsi'' is an extinct sponge from the late Ediacaran, with possible affinities to the Archaeocyatha. Estimated to be about 543 million years old, ''A. germsi'' has been identified as possibly being the oldest known archaeocyathan to d ...

References