Ctenacanthiformes
| Ctenacanthiformes | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Sphenacanthus from the Early Carboniferous of Scotland |
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| Temporal occurrence | ||||||||||||
| Middle Devonian to Triassic | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Ctenacanthiformes | ||||||||||||
| Zangerl , 1981 |
The Ctenacanthiformes are the most important group of extinct, shark-like cartilaginous fish . Among them are likely the ancestors of today's sharks and rays . They lived from the Middle Devonian to the Triassic .
features
The Ctenacanthiformes had two dorsal fins, each provided with a strong thorn . The spines had an outer layer of enameloid , an enamel-like substance, were rooted deep in the muscles of the back and were supported on the back by triangular cartilage plates. The anal fin was located far back just in front of the heterocerkic, externally symmetrical caudal fin . Like the modern Elasmobranchii , the Ctenacanthiformes had a three-base pectoral fin skeleton . Her teeth were cladodont. The notochord had no constrictions. The fish were up to 2.5 meters long.
Systematics
The Ctenacanthiformes are divided into three families. Two genera are incertae sedis and cannot be assigned to any family.
- Acronemus
- Carinacanthus
- Family Ctenacanthidae , Upper Devonian to Mississippian
- Family Bandringidae , Pennsylvania , mainly in fresh water, snout with elongated rostrum
- Family Phoebodontidae , Middle Devonian to Upper Triassic
- Family Thrinacodontidae , Lower Carboniferous
Since the Hybodontiformes and the modern sharks and rays, the Neoselachii , emerged from the Ctenacanthiformes, they are considered paraphyletic .
literature
- 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 3-13774-401-6 .
Individual evidence
- ↑ Grogan, ED, and Lund, R., 2008, A basal elasmobranch, Thrinacoselache gracia n. Gen. & Sp (Thrinacodontidae, new family) from the Bear Gulch Limestone, Serpukhovian of Montana, USA : Journal of Vertebrate Paleontology, v. 28, n. 4, p. 970-988.
