6533b86dfe1ef96bd12c949c

RESEARCH PRODUCT

Apparition d'une morphologie scaphitomorphe par miniaturisation chez une ammonite oxfordienne : Scaphitodites scaphitoides ()

Didier MarchandJacques RossiPascal NeigeetJacques Lance

subject

AmmonitebiologyOcean EngineeringAmmonoideaAnatomybiology.organism_classificationlanguage.human_languageCretaceousPaleontologyAdult sizeSensuGenusPhanerozoiclanguageMesozoicEcology Evolution Behavior and SystematicsGeology

description

The pyritized fossil-bearing marls of the Jura (Lower Oxfordian) contain an ammonite that is remarkable because of its tiny adult size (less than 16 mm) and of the scaphitoidal coiling of its body chamber, which is similar to that of certain Cretaceous Scaphitaceae. Anatomical and ontogenetic analysis demonstrates that these individuals, which are ascribed to Scaphitodites scaphitoides (Coquand, 1853), formed a single species. We argue that the genus Scaphitodites derived from Taramelliceras by a complex process of progenesis (sensu Landman et al., 1991).

https://doi.org/10.1016/s1251-8050(97)88301-2