Systematic Paleontology
Order Bactritida
Family Bactritidae
Genus Kokenia
Kokenia is a bactritid genus that lived during the latter part of the Middle Devonian, apparently derived from Bactrites, and which give rise to nothing else.
The shell of Kokenia is exogastrically cyrtoconic, as with the ammonoid ancestor Cyrtobactrites; almost gyroconic. Curvature is such that the venter with siphuncle is on the outer convex side, and such as to be nearly coiled but without whorls in contact. Whorl sections are oval, whorls bearing ribs. In the early juvenile stages sutures have a small ventral lobe, deeply rounded lateral lobes, and a prominent dorsal saddle. In the late ontogenetic (growth sequence) stage the ventral lobe is replaced by a ventral saddle and the siphuncle shifts from ventral to subventral, separating from the ventral wall.
Kokenia, named by Holzapfel in 1895, has been found in central Europe.
References
H. K. Erben 1964. Bactrioidea. Treatise on Invertebrate Paleontology, Part K. Kokenia fig 358.6 p. K500, & p. K501
Kokenia in Sepkoski, J.J. Jr. (2002). A compendium of fossil marine animal genera. Bulletins of American Paleontology 363: 1–560. [1]