Blastoid
Several Thekae of Blastoids
- Worldwide
The buds radiator ( Blastoidea AltGr. Βλαστός, stem ') are an extinct genus within the tribe of echinoderms ( Echinodermata ) and are living today sea lilies and feather stars ( Crinoidea class, subphylum Crinozoa ) distantly related. In the scheme, the buds spotlight with about 80 genera along with the other extinct genera Eocrinoidea, Cystoidea (bag lamps), Paracrinoidea and Parablastoidea be bundled into the trunk Blastozoa.
The origin of the buds radiator is unclear, a descent from the Eocrinoidea or Ordovician Cystoidea is contemplated. From the Silurian two main groups ( Fissiculata and Spiraculata ) were represented. The Fissiculata were in the Devonian and Lower Carboniferous of different shapes, their main flowering period they had in the Permian. The Spiraculata were always richer form in Devon and had their main flowering period in the Lower Carboniferous. Only a few stragglers reached up into the Permian.
Most Blastoids had - like the Crinoideen - a person sitting on a stem body capsule ( theca ), which consisted of tablets and a rigid armor was formed. Typical of the Blastoids were the Hydrospiren, a characteristic system of ( suspected ) Respiratory openings in the upper part of the theca. On the theca were many, fixed existing brachioles essentially consists of two alternating rows of plates.
Coverslips, crinoid and Brachiolenplättchen dissolved after the death of the individual rapidly from the theca and were often embedded isolated. They must be distinguished from the corresponding elements of Crinoideen hardly and are usually mistakenly addressed as " Crinoideen - Schill ".
Especially often they are found in the Lower Carboniferous of North America and in the Permian of the island of Timor.
Way of life
The buds emitters were exclusively marine and subsisted by filtered fressbare particles with their brachioles from the passing water and led to the mouth. Most buds were spotlight - as sea lilies - constantly with a stem attached to the sea floor ( sessile ).