Lissoceras

Lissoceras is an involute, smooth or finely vetrolaterally ribbed, ammonite with a blunt, un-keeled venter, included in the Haploceratidae, that lived from the Lower Bajocian - Middle Oxfordian (Middle to Upper Jurassic) in what is now Europe, south Asia, and southern Alaska.

Lissoceratoides, once considered to be a subgenus of Lissoceras, is indistinguishable morphologically from it.