Semionotus
| Semionotus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Fossil of Semionotus bergeri in the State Museum for Natural History Stuttgart . |
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| Temporal occurrence | ||||||||||||
| Norium (Upper Triassic) to Lower Sinemurian (Lower Jurassic) | ||||||||||||
| 228 to ~ 192 million years | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Semionotidae | ||||||||||||
| Woodward , 1890 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Semionotus | ||||||||||||
| Agassiz , 1843 |
Semionotus is an extinct genus of bony fish thatoccurredin the lower Mesozoic in flat coastal regions of the Tethys . The genus was established in 1843 by the Swiss-American naturalist Louis Agassiz and subsequently developed into a collective genus of all possible Mesozoic ray fins that were often poorly prepared, examined and diagnosed . In January 2012 the genus was re-described by the paleontologist Adriana López-Arbarello.
features
Semionotus species were medium-sized fish with moderately elongated bodies. Its head was elongated, its muzzle pointed. The eyes were surrounded by a ring-shaped, bony reinforcement. The pin-shaped teeth had rounded tips. On the back, in front of the dorsal fin, there was a noticeable ridge of keeled scales. The dorsal fin was relatively large, the anal fin further back was smaller. The heterocerke caudal fin was slightly indented. The rays of the lower lobe of the caudal fin, not supported by the spine, were carried by eight lepidotrichia . The scales were diamond-shaped ganoin scales .
Systematics
Semionotus belongs to the Semionotidae family, which was established in 1890 by the British paleontologist Arthur Smith Woodward . The Semionotidae today include all taxa that are more closely related to Semionotus bergeri than to Callipurbeckia , Macrosemius , Lepidotes or Lepisosteus . This makes Semionotus the only genus of the Semionotidae that is basal to the Callipurbeckiidae family . Both taxa together are in a sister group relationship to the Macrosemiidae . All three families form the semionotiformes .
literature
- Adriana López-Arbarello: Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterygii). PLoS ONE , doi : 10.1371 / journal.pone.0039370
- Karl Albert Frickhinger: Fossil Atlas of Fishes. Mergus, Verlag für Natur- und Heimtierkunde Baensch, Melle 1999, ISBN 3-88244-018-X .
Web links
- The Paleobiology Database: Semionotus Agassiz, 1843