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Upper upper Albian (Mortoniceras rostratum Zone) cephalopods from Clansayes (Drôme, south-eastern France)

Jattiot Romain, Lehmann Jens, Latutrie Benjamin, Tajika Amane, Vennin Emmanuelle, Vuarin Pauline, Brayard Arnaud, Fara Emmanuel, Trincal Vincent

Acta Geologica Polonica

2022

Vol. 72, no. 2

187--233

We document an upper upper Albian (Mortoniceras rostratum Zone) cephalopod assemblage from Clansayes (Drôme, south-eastern France). Although fossils are rare in local exposures and in the single sampled level, a decade of intensive fossil collecting yielded 290 ammonite and 5 nautilid specimens. In total, we describe 1 species of nautilid and 24 species (within 17 genera) of ammonites, including 13 heteromorphs. Only two of these ammonite taxa were previously recorded from the upper upper Albian at Clansayes, which demonstrates the value of this fauna with regard to taxonomy, palaeobiology and palaeobiogeography. Based on morphological and biometric analyses performed on an extensive material (104 specimens), we discriminate two species for the heteromorphic ammonite genus Mariella Nowak, 1916 within the Mortoniceras rostratum Zone. In addition, we investigate shell chirality patterns in Mariella from the late Albian of southern France. Upon comparison of the Clansayes material with older material from the immediately underlying upper Albian Mortoniceras fallax Zone at the neighbouring Salazac locality, we identify an increase in the proportion of sinistral specimens. This observed increase in the frequency of sinistral Mariella specimens may hypothetically be part of a global evolutionary pattern, considering that nearly all documented younger Cenomanian Mariella (and more generally Cenomanian turrilitids) are sinistral.

Ontogeny and variability in ribbing of Late Valanginian lamellaptychi (Ammonitina)

Vašíček Z., Klein J., Janssen N. M .M.

Annales Societatis Geologorum Poloniae

2016

Vol. 86, No. 1

17--28

Late Valanginian (Early Cretaceous) lamellaptychi of the genus Mortilletilamellaptychus were collected from seven ammonite-controlled sections in south-eastern France demonstrate distinct changes in ribbing during growth. Simpler juvenile ribbing, which is essentially uniform for all of the specimens studied, differs distinctly from the complicated arrangement of the adult ribs. Changes in ribbing morphology were observed in the five species studied, two of which were identified as new (i.e. Mortilletilamellaptychus heterocostatus sp. nov. and M. bicostatus sp. nov.).

Palaeontology, taxonomic revision and variability of some species of the genus Gassendiceras Bert et al., 2006 (Ammonitina, Upper Barremian) from southeastern France

Bert D., Bersac S., Delanoy G., Canut L.

Acta Geologica Polonica

2013

Vol. 63, no. 3

355--397

Bed-by-bed sampling of twelve Barremian sections in southeastern France from pelagic basin (Vocontian Basin) to neritic platforms (Arc of Castellane, Arc of Nice and Provencal Domain) has enabled the collection of isochronous samples of the ammonite genus Gassendiceras. Three poorly known species of the Toxancyloceras vandenheckei Zone (Upper Barremian) are revised: G. alpinum, G. multicostatum and G. hoheneggeri; two new species are described (G. rebouleti nov. sp. and G. bosellii nov. sp.). The intraspecific variability of particular species was recognised. This variability is between slender peramorphic and robust paedomorphic extreme morphologies, with the presence of all intermediates.