Radiocyatha is an extinct group of

sponge Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...

-like animals which lived in the early to mid-

Cambrian Period The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovici ...

(

Tommotian Stage 2 of the Cambrian is the unnamed upper stage of the Terreneuvian Series. It lies atop the Fortunian and below Stage 3 of the Cambrian. It is commonly referred to as the Tommotian, after the Cambrian stratigraphy of Siberia. Neither the uppe ...

Toyonian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission ...

Details

They were very similar to archaeocyath sponges, with a cup-shaped

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

body up to 20 cm (7.9 inches) in height. One major difference is that the radiocyath skeleton is not composed of tiny

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

grains, but rather large

aragonite Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...

plates, known as nesasters. Nesasters are star-shaped, with up to 20 radiating spokes in a flat plane. The outer wall of the cup has radial rods directed inwards. ''Uranosphaera'' is a simple single-walled radiocyath, while the hetairacyathids bear an additional nested wall layer, akin to archaeocyaths.''Treatise on Invertebrate Paleontology'' Part E, Revised. Porifera, Volumes 4 & 5: Hypercalcified Porifera, Paleozoic Stromatoporoidea & Archaeocyatha, liii + 1223 p., 665 figs., 2015, availabl
here
. Radiocyaths reached their maximum abundance in the

Atdabanian Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approxi ...

and

Botomian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission ...

, contributing towards the biomass of archaeocyath sponge

reefs A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic (non-living) processes such as deposition of sand or wave eros ...

in regions such as Mongolia and Australia. Sponge affinities for radiocyaths are plausible but uncertain; the snowflake-shaped

spicules Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

of heteractinid sponges show some similarity to nesasters. Radiocyaths have been compared to the enigmatic receptaculitids, which also have calcareous plates and radiating rod-like structures. Radiocyatha is tentatively ranked as a

class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...

Subgroups

* '' Uranosphaera'' Bedford & Bedford, 1936 otomian 1 – 3* Order Hetairacyathida / Family Hetairacyathidae Bedford & Bedford, 1937 ** '' Blastasteria'' Debrenne et al., 1971 otomian 3** '' Radiocyathus'' Okulitch, 1937 tdabanian 4 – Botomian 3** '' Girphanovella'' Zhuravleva, 1967 tdabanian 1 – Toyonian 2** '' Gonamispongia'' Korshunov, 1968 ommotian 3 – Atdabanian 1

References

{{Taxonbar, from=Q118378313 Cambrian sponges Cambrian animals Prehistoric animal classes