Hyolithids
| Hyolithids | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
||||||||||||
| Temporal occurrence | ||||||||||||
| Cambrian to Wuchiapingian (Upper Permian) | ||||||||||||
| 542 to 255 million years | ||||||||||||
| Locations | ||||||||||||
|
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Hyolitha | ||||||||||||
| Matthew , 1899 |
The Hyolithiden or Calyptomatida are a group of animals that existed in the Lower Cambrian to the Middle Permian and died out at the end of this period. They became widespread in the Cambrian and Ordovician , but often also in many places in the Silurian and Devonian , rarely in the Carboniferous and Permian.
Their systematic position was not known exactly for a long time. They were assigned to the tribe of the mollusks and therefore also called swimming snails or primeval mollusks. The exact examination of the tentacles emanating from the mouth of newly discovered fossils from the Canadian Burgess schist showed that they are similar to the tentacle wreath ( Lophophor ) of the armpods (Brachiopoda) and that the hyolithids can therefore be classified into the Lophotrochozoa .
Hyolithids form bilaterally symmetrical, up to 15 cm long conical limestone casings with a triangular, elliptical, circular or pentagonal cross-section. One side is usually flattened, the other domed or blunt keeled. Most representatives use a concentrically striped lid to close the mouth. The rotatable horns were used for props.
Nothing more can be said about their ecology, but due to the soft body preservation of paired fin-like appendages in some species, a free-swimming way of life is assumed. A sessile way of life anchored on the sea floor is also conceivable, although they were tip-first in the bottom sediment. They were probably shallow sea benthos who lived on suspended organic matter. Natural enemies were Priap worms of the species Ottoia prolifica , which are found in the Cambrian of the Burgess slate .
Individual evidence
- ↑ Joseph Moysiuk, Martin R. Smith, Jean-Bernard Caron. Hyoliths are Palaeozoic lophophorates. Nature , 2017; DOI: 10.1038 / nature20804
Web links
- The Paleobiology Database Hyolithida
- Reconstruction of a hyolith