Abstract
Belemnite rostra bear longitudinal furrows of various kinds, ranging considerably in strength. The present systematic classification of belemnites is based on characters other than the generally indistinct marginal or lateral furrows which, nevertheless, are important because they probably are attachment scars for the fins. One reason for their neglect by taxonomists in belemnite classification is that they are not useful for differentiation of genera, but tend to remain fairly constant within the subfamily. A study of several thousand specimens shows that Cylindroteuthis and Pachyteuthis, represented by 13 species, have a similar pattern of lateral grooves and belong in the same subfamily (Cylindroteuthinae). A different pattern common to Aulacoteuthis and Oxyteuthis shows that these genera were correctly united by Stolley in a different subfamily (Oxyteuthinae). Attention to details of the lateral grooves will also permit working out the phylogeny of major stocks, such as the descent of Belemnitellinae ...
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