Short Guide To Solnhofen Fishes

[oilshale]

Amblysemius was clearly a predator as evidenced by its mouth full of sharp teeth. It was a notable fast swimmer possessing an elongated, somewhat thickset body with slender head. Together with its only sister genus Caturus, Amblysemius was a member of the extinct Halecomorpha family Caturidae. It appears that the halecomorph Liodesmus, known from Solnhofen only, is related to the Caturids, rather than the Amiiforms, as has been usually surmised. Once a diverse major group of bony fishes, the Halecomorpha have only one surviving member, the bowfin (Amia calva) of eastern North America. Living bowfins are remarkably hardy since they have a swim bladder that opens into their esophagus so they can gulp air, and hence survive in water with low oxygen. Amblysemius was a primitive species of fish that thrived during the Jurassic Period but went extinct by the Lower Cretaceous Period. Amblysemius possessed ganoid scales that are more cycloid in nature and as a member of the holosteans a bony skeleton with a partially ossified vertebral column.

The Caturidae are represented in the Solnhofen Formation by at least four species:

Caturus furcatus Agassiz 1834 and Caturus giganteus Wagner, 1851. Caturus pachyurus Agassiz, 1833 and Caturus bellicianus Thiollière 1852 from Solnhofen, Germany and Cerin, France.

The last two species were transferred to the revived sister genus Amblysemius (now Amblysemius pachyurus and Amblysemius bellicianus).

Compared to Caturus, Amblysemius is characterized by its more slender body outline, the bigger and more deeply forked caudal fin being heterocerc with the upper lobe clearly longer than the lower one and the strong dentition. Amblysemius has considerably smaller scales compared to Caturus. Maximum length is around 50cm.

This is a medium size Amblysemius bellicianus from Eichstätt.

This slab and counter slab of an Amblysemius is from Solnhofen.

Compared to other Amblysemius I've seen from Solnhofen, this fish has an even larger caudal- but smaller anal-, pelvic- and dorsal-fins - so it might be an new and undescribed Amblysemius species.

[Ludwigia]

Thank you for this very informative article, Thomas. As usual very well done and detailed. I think I'll probably be in Solnhofen this summer, so now I'm getting my hopes up for a nice fish!

Roger

[fossilshk]

Germany fossils is very beautiful.