Modalités évolutives du genre bullatimorphites (Ammonitina) au Bathonien-Callovien (Jurassique moyen) en Europe occidentale

1999

Abstract The genus Bullatimorphites, (macroconchs Bullatimorphites, Kheraiceras; microconchs Bomburites, Schwandorfia, Spbaeroptycbius, Treptoceras), is characterized by an ontogenesis with three morphologic phases: serpenticone, sphaerocone and ellipticone. Within the successive populations, the relative development of these morphologies allows the defined species to be placed in an evolutive and stratigraphic lineage. The history of the genus comprises five steps: 1) emergence (Early Middle Bathonian), 2) first gradual evolution (Middle-Upper Bathonian), 3) first morphological diversification (Uppermost Bathonian), 4) second gradual evolution, 5) second morphological diversification and e…