Troedssonellidae Kobayashi 1935

Family Troedssonellidae Kobayashi, 1935

In the cladistic analyses (see below), Troedssonella Kobayashi, 1935 was not recovered within the same clade as other typical troedssonellids such as Buttsoceras Ulrich & Foerste, 1933, Tajaroceras Hook & Flower, 1977 and Moridunoceras Evans, 2005. Therefore, the Troedssonellidae may be polyphyletic and Troedssonella is perhaps more closely related to the Orthoceratidae instead. Since Troedssonella is the type genus of the family, this would require an emendation of the family and a new family for Buttsoceras and allied genera. However, because of the unclear relationships between many Floian dissidocerids, including the Rangeroceratidae and the Polymeridae, we refrain from establishing another family here, but point out the necessity for further studies on these relationships.