Mongoceras

As with the Orthocerida the shell of Mongoceras is generally long and straight, with a generally central siphuncle composed of thin connecting rings. A vertical, heads down orientation in life can be inferred, in contrast with the horizontal benthic orientation of ellesmerocerida, endocerids, and many actinocerids with their weighted ventral siphuncles.^[3]

Mongoceras has been found with Kionoceras, Geisonocers, and Sichuanoceras in Silurian reefoid formations in China, along with a suite of other benthic invertebrates. It has also been found in core samples from Siberia with Edenoceras hiliferum and Geisonoceras kureikense.^[3]