| Radiocyatha | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Porifera (?) |
| Class: | †Radiocyatha Debrenne et al., 1970 |
Radiocyatha is an extinct group ofsponge-like animals which lived in the early to mid-Cambrian Period (Tommotian toToyonian).
They were very similar toarchaeocyath sponges, with a cup-shapedcalcareous body up to 20 cm (7.9 inches) in height. One major difference is that the radiocyath skeleton is not composed of tinycalcite grains, but rather largearagonite 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.[1]
Radiocyaths reached their maximum abundance in theAtdabanian andBotomian, contributing towards the biomass of archaeocyath spongereefs in regions such as Mongolia and Australia. Sponge affinities for radiocyaths are plausible but uncertain;[1] the snowflake-shapedspicules ofheteractinid sponges show some similarity to nesasters.[2] Radiocyaths have been compared to the enigmaticreceptaculitids, which also have calcareous plates and radiating rod-like structures.[3] Radiocyatha is tentatively ranked as aclass.[1]