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Invertebrata |
Department of Geology, University College, Gower Street, London W C 1
Department of Geology, King’s College, Strand, London W C 2
There is disagreement at the present time on the classification of the earliest Belemnoidea, and their relation to the Bactritoidea from which they are probably derived (see Flower and Gordon 1959, Shimansky 1960, Erben 1964, Jeletzky 1965). There is no doubt that there are belemnoids at least as early as the Namurian, but the variety of this fauna suggests that they had developed before this (Upper Devonian?). Their similarity to the Parabactritidae of Shimansky is such that Flower and Gordon thought that the Parabactritidae might be belemnoids, but Shimansky and Erben are convincing in making a distinction, although Erben suggests that the Belemnoidea s.s. are derived from the Parabactritidae. A fragment, which may be a belemnoid, from the Devonian (Eifel?) of Couvain, Belgium, is figured by Koninck (1843).
The classification used here is conservative. For Jeletzky the only pre-Jurassic belemnoid is Eobelemnites Flower (Namurian), and the forms here considered under the subfamily Aulacoceratinae are assigned to a separate order—the Aulacocerida. For Erben some of the Aulacoceratinae are Belemnoidea s.s. (e.g. Mojsisovicsteuthis convergens (v. Hauer) from the Karnian), and some are a separate order the Protobelemnoidea which Erben believes are derived from the Bactritidae, not the Parabactritidae.
There is disagreement on what is the last belemnoid. There are genera which are intermediate between belemnoids and sepiids. I have placed Bayanoteuthis (Eocene), which probably had a rostrum of calcite, in the Belemnoidea. But Styracoteuthis (Eocene) whose rostrum has lost all the details of its internal structure through recrystallisation, was probably of aragonite (like Vasseuria, see
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