Helodus
| Helodus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Helodus simplex |
||||||||||||
| Temporal occurrence | ||||||||||||
| Oberdevon to Unterperm | ||||||||||||
| 339.4 to 260.5 million years | ||||||||||||
| Locations | ||||||||||||
|
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name of the family | ||||||||||||
| Helodontidae | ||||||||||||
| Patterson , 1965 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Helodus | ||||||||||||
| Agassiz , 1838 |
Helodus was a small cartilaginous fish thatlivedfrom the Upper Devonian to the Lower Permian . Fossils , mostly teeth and dental plates, have been found in North America, Europe, and Australia.
features
Helodus was only 30 cm long and had a dorsoventrally somewhat flattened body covered with small scales. The caudal fin was slightly heterocercous , the second dorsal fin was relatively far back. It was spineless, while the first dorsal fin was supported by a laterally flattened, smooth spine. As with the recent sea cats (Chimaeriformes), the two halves of the basin had not grown together. The pectoral fins were dibasal and connected to the shoulder girdle by a long metapterygium and a short propterygium . They were only supported by short, anterior radialia (fin rays of the cartilaginous fish). The forehead is without a head hook.
In the jaws sat several rows of teeth that were more or less fused into tooth plates. The crowns of the teeth were flat or pointed.
literature
- Arno Hermann Müller: Textbook of paleozoology. Volume III, Vertebrates, Part 1. Gustav Fischer Verlag, 1985.