Anaspida
| Anaspida | ||||||||||||
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Pharyngolepis (above), rhyncholepis (below), |
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| Temporal occurrence | ||||||||||||
| Silurian to Upper Devonian | ||||||||||||
| 440 to 370 million years | ||||||||||||
| Locations | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Anaspida | ||||||||||||
| Janvier , 1996 |
The Anaspida , also called Anaspidida , are a group of extinct, jawless, fish-like vertebrates that lived from the Silurian to the Upper Devonian. The recent lampreys were considered their closest relatives. Some bare, scaleless forms, e.g. B. Jamoytius kerwoodi have occasionally been counted among the lampreys . Today the Anaspida are placed more in phylogenetic proximity to the jaws (Gnathostoma).
features
The body of the Anaspida was elongated, spindle-shaped and somewhat flattened on the sides. Of all the jawless ones, they most closely resembled "normal" fish. The animals did not have massive head and body armor, like most Paleozoic jawless ones. They had a terminal mouth and 6 to 15 small, outer gill openings that ran diagonally from the back of the head to the side of the abdomen. At the end of the row of gills was a three-pointed stinger. The caudal fin was hypocerk . Except for the caudal fin, all the fins were on the ventral side, a pair of low fin fringes from the end of the three-pointed spine to the anal opening and an anal fin, which was missing in later forms, behind the anal opening.
Most forms of the Obersilur were scaled, with Jamoytius and Lasanius from the Obersilur and the forms of the Devonian scales were only slightly or not at all developed.
The middle of the back was covered by a characteristic row of scales. The maximum length was 15 cm. They probably lived as filter feeders. Their internal anatomy is unknown.
Genera
literature
- Hans-Peter Schultze: Anaspidida , page 193 in Wilfried Westheide & Reinhard Rieger : Special Zoology Part 2: Vertebrae and Skull Animals , 1st edition, Spectrum Academic Publishing Heidelberg • Berlin 2004, ISBN 3-8274-0307-3 .
- Joseph S. Nelson : Fishes of the World . John Wiley & Sons, 2006, ISBN 0-471-25031-7 .
- Robert L. Carroll: Paleontology and Evolution of the Vertebrates , Thieme, Stuttgart (1993), ISBN 3-13-774401-6 .
Web links
- Janvier, Philippe: Anaspida. Version 01 January 1997. in The Tree of Life Web Project