Lissoceras is an involute, smooth or finely vetrolaterally ribbed, ammonite

Ammonitida

The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....

 with a blunt, un-keeled venter, included in the Haploceratidae

Haploceratidae

The Haploceratidae is one of the families to go to form the Haplocerataceae, a superfamily in the ammonitina; which according to Donovan et al can be derived from the Taramelliceratinae, a subfamily of the Oppeliidae....

, that lived from the Lower Bajocian

Bajocian

In the geologic timescale, the Bajocian is an age or stage in the Middle Jurassic. It lasted from approximately 171.6 Ma to around 167.7 Ma . The Bajocian age succeeds the Aalenian age and precedes the Bathonian age....

 - 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.