Fig. 4From: Lissajousibelus nov. gen., an Early Jurassic canaliculate belemnite from Normandy, FranceStratigraphical distribution of the discussed taxa in the order of first occurrence. The morphological trends in the ventral groove element are evidenced by the pattern of the vertical distribution lines (transparent: presence of an apical ventral groove, without splitting surface; grey shaded: intermediate ventral groove, with more or less developed splitting surface; black: alveolar ventral groove, with fully developed splitting surface). Chronostratigraphy is in accordance with Cohen et al. (2013)Back to article page