Middle Albian (Lower Cretaceous) gastroplitinid ammonites and dinoflagellates from the Christopher Formation (Dragon Mountain, Axel Heiberg Island, Canadian Arctic Islands) and a revision of the genus Pseudogastroplites Jeletzky, 1980. Journal of Paleontology, 79(2), March 2005: 219-241. 227 [Zoological Record Volume 141]