Archaeocyathids

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Archaeocyathids
Anatomy of an archaeocyathid. 1 = interval, 2 = central cavity, 3 = inner wall, 4 = pore, 5 = pseudo-prescription, 6 = outer wall, 7 = exothecal outgrowths.

Anatomy of an archaeocyathid. 1 = interval, 2 = central cavity, 3 = inner wall, 4 = pore, 5 = pseudo-prescription, 6 = outer wall, 7 = exothecal outgrowths.

Temporal occurrence
upper Ediacarian ( Tommotium ) to lower Cambrian
590? up to 516? Million years
Locations
  • worldwide
Systematics
Domain : Eukaryotes (Eucaryota)
without rank: Opisthokonta
without rank: Holozoa
without rank: Multicellular animals (Metazoa)
Sponges (Porifera)
Archaeocyathids
Scientific name
Archaeocyatha
Vologdin , 1937

The Archaeocyathiden or Archaeocyatha (Archaeocyatha) are a reef-building group of animals similar to the sponges that appeared in the Upper Ediacarium as part of the Small Shelly fauna and became extinct after the Lower Cambrian . In the Lower Cambrian, they were the third most common group of animals and are now important key fossils . Their calcareous housings are well preserved from fossils. They account for about 5% of the known species.

In most of Europe their fossils are quite rare, but occur very often in southern Sweden, Öland , the Baltic States , Morocco , North America, Siberia and Australia directly above the almost fossil-free Precambrian sediments. In Germany archaeocyaths have been found in the Lower Cambrian Eodiscidenschiefer near Görlitz , Delitzsch and Torgau . In 2014 archaeocyaths were also discovered in the Franconian Forest and exposed by the Bavarian State Office for the Environment . Fossils in Sardinia are so well preserved that they were made into gemstones. The attempt to manufacture natural stone tiles from the red flaser lump, in which the archaeocythids occur in Sardinia, was discontinued. On the site of this factory in Grugua (Fluminimaggiore) you can find these fossils in the polished remains of tiles, they come from the lower Cambrian, Nebida Formation, Maloppa layers.

The archaeocyaths lived at depths of 20 to 50 meters in the sea on carbonate floors and formed shallow reefs . In the archaeocyathic reefs also lived algae, armwort and trilobites , as well as hyolithids , echinoderms and other sponges.

features

They had a funnel-shaped to barrel-shaped body that was firmly seated on the ground and was subdivided by radial dividing walls or chamber partitions, the pseudosepta. As with the higher sponges, the limestone structure was hollow. Archaeocyaths fed on filtration . Water entered through the porous outer wall, was filtered and exited again at the top through the central outflow opening. It is unknown whether the water transport was active, through cilia , or purely physically.

The archaeocyaths were solitary, some also formed colonies . In most cases, their height was between 8 and 15 centimeters, and the diameter of the central outlet opening was one to two centimeters. The genus Okulitchicyathus , which forms a wavy, flat disk , could reach a diameter of 60 centimeters.

Since they were never found at depths below 100 meters, they probably lived with photosynthetic organisms similar to zooxanthellae. Due to their widespread distribution, a planktonic larval stage is assumed. Their systematic position is not exactly known. Presumably they were a specialized group of sponges. The cause of their extinction is unknown.

literature

  • Storch, Welsch, Wink: Evolutionary Biology. Pages 73-75, Springer, 2001, ISBN 3-540-41880-6

Web links

Commons : Archaeocyatha  - collection of images, videos and audio files