The Cheiron Mountain (Alpes-Maritimes, southeastern France) sample of Tornquistes Lemoine was collected in the Arkelli Biohorizon (Vertebrale Subzone, Plicatilis Biozone). Its study reveals its homogeneity whereas its morphology is between two nominal and classical species of literature : Tornquistes tornquisti (de Loriol) and Tornquistes oxfordiense (Tornquist). It appears that the features
... [Show full abstract] usually taken into account to establish specific denominations in this genus (whorl section thickness, strength and density of the ornamentation, widening of the umbilicus) are in fact manifestations of the laws of covariation of the characteristics, and the extreme morphologies are interrelated by all intermediaries. There is now no taxonomical reason not to consider all the nominal taxa described in the Plicatilis Biozone as a single paleobiological species : Tornquistes helvetiae (Tornquist). On the other hand, the stratigraphic polarity of the position of the primary ribs point of bifurcation (which decreases through time) is a major evolutionary feature in Tornquistes. It now allows defining at least three, maybe four, successive chronospecies : (1) (?) Tornquistes greppini (de Loriol), (2) Tornquistes leckenbyi (Arkell ), (3) Tornquistes helveticus (Jeannet) and (4) Tornquistes helvetiae (Tornquist). Finally, although Protophites Ebray has often been regarded as a microconch, it is clearly not the one of Tornquistes. The oldest species of Protophites now recognized is Protophites chapuisi (de Loriol) at the top of the Mariae Biozone (Praecordatum Subzone).
