Kosmoceras sp.

It has been a long time since I posted anything here. But now I’m back with something new to share.

This is a fossil ammonite from Middle Jurassic (Callovian), 165 million years ago, from Mikhaylov in the region of Ryazan, Russia. It seems to be some kind of Kosmoceras (Waagen 1869) but I’m not quite sure which species, it might be a Kosmoceras (S. Str.) baylei (Tintant 1963).

Remains of a Kosmoceras sp. in anterior (left) and left lateral (right) views.
Ink on drawing film, revision in Photoshop.

The living chamber and the innermost part have not been preserved. The shell of the living animal would have been more than twice as large. The chambered inner part of the shell was virtually surrounded by the living chamber, which was slightly longer than one spiral turn.

I purchased this specimen a few years ago, because it is preserved with its beautiful nacre shell.


Tintant, H. 1963. Les Kosmocératidés du Callovien inférieur et moyen d’Europe occidentale. Essai de paléontologie quantitative. Les presses universitaires de France 64:1-500.

Waagen, W. 1869. Die Formenreihe der Ammonites subradiatus. Geognostisch-paläontoligischen Beiträge 2:179-256.


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