Dr. Landman’s interests include the evolution, life history, and systematics of externally shelled cephalopods, particularly the twin groups-the ammonoids and nautiloids.  Both have a superb fossil record comprising about 10,000 species. His investigations have focused on the early ontogenetic development of ammonoids and nautiloids, and how this information can be used to reconstruct the phylogeny of these groups.  He also studies the evolution and systematics of ammonoids from Upper Cretaceous rocks of the Northern Great Plains in the United States.  Fieldwork in Montana, South Dakota, and Wyoming has resulted in an extensive collection of these ammonoids, which were plentiful in the seaway that once covered this part of North America during the Cretaceous Period.  In addition to their systematics, he is concerned with the distribution of these species in time and space, and in relation to their paleoenvironment.