Part M, Chapter 23B: Systematic Descriptions. Aulacoceratida

(This Chapter has no Abstract. From the Introduction, the following excerpt is given:) The order Aulacoceratida Stolley, 1919 is a group of rostrum-bearing orthoconic coleoids, which was established as distinct from true belemnites starting with Bather in Blake (1892). Schwetzov (1913), Abel (1916), Stolley (1919), Naef (1921b), and Jeletzky (1966) recognized its independence from the Belemnitida Zittel, 1895. Later, the order was further circumscribed, and various taxa were reassigned to other belemnoid orders (Belemnitida, Hematitida Doguzhaeva, Mapes, & Mutvei, 2002, and Phragmoteuthida Mojsisovics, 1882) (Engeser, 1990). The Aulacoceratida comprise 15 genera, belonging to three families grouped into two superfamilies (Aulacoceratoidea Mojsisovics, 1882 and Xiphoteuthidoidea Bather in Blake, 1892), and in addition two genera incertae sedis. They are mainly characterized by a long and tubular (i.e., ventrally closed) body chamber (see Donovan & Riegraf, 2016, Treatise Online, Part M, Chapter 21) and an aragonitic and massive rostrum (e.g., Jeletzky, 1966).