Based on examination of the type material deposited by Jacques Sigal at the Musée National d'Histoire Naturelle in Paris, we have validated the hypothesis of Randrianasolo and Anglada (1998) that the holotype and para type of Ticinella bejaouaensis Sigal 1966 belong to two different species, the distributions of which do not overlap. Indeed, the holotype is of late Albian age and from Madagascar whilst the paratype is of a latest Aptian age and from Tunisia. Sigal's paratype is here confirmed to be the holotype of the species eubejaouaensis Randrianasolo and Anglada, 1998. It displays a distinctive wall texture bearing perforation cones that coalesce to form irregularly arranged rugosities and ridges, which tend to parallel the periphery. In addition, flaps may cover the umbilical area. However, it lacks true umbilical supplementary apertures and therefore cannot be included in the genus Ticinella Reichel, 1950. The new genus Paraticinella, with Paraticinella eubejaouaensis as the type species, is here formalized to accommodate uppermost Aptian trochospiral individuals with a wall texture bearing perforation cones, rugosities, and ridges in patterns paralleling the margin, and possessing an umbilical cover-plate. Paraticinella eubejaouaensis evolved from Hedbergella trocoidea in the upper Aptian. The evolutionary trend is exemplified by the increasing number of chambers, by flattening of the spire height, by widening of the umbilicus with the appearance of a cover-plate, by acquisition of well-developed ridges on wall surfaces, and by the appearance of weakly developed infralaminal accessory apertures in later specimens of P. eubejaouaensis. A close study of the holotype of Ticinella bejaouaensis Sigal, 1966 reveals a substantial similarity in morphology and wall structure with Ticinella roberti and a lack of distinguishing criteria between the two species. Consequently, the species Ticinella bejaouaensis is invalidated and is considered to be a junior synonym of T. roberti. A third species was observed associated with Ticinella roberti and Biticinella breggiensis in Madagascar and Spain, and it is attributable to the genus Ticinella based on the presence of true umbilical supplementary apertures and a typical Ticinella wall structure (muricate to coarsely pustulose), while in gross morphology, it resembles Paraticinella eubejaouaensis. We have named this new taxon Ticinella moulladei. It differs from T. roberti by its thinner test, more numerous chambers, and wider umbilicus.
|Titolo:||Paraticinella n. gen. and taxonomic revision of Ticinella bejaouaensis Sigal, 1966|
PREMOLI SILVA, ISABELLA (Primo)
|Settore Scientifico Disciplinare:||Settore GEO/01 - Paleontologia e Paleoecologia|
|Data di pubblicazione:||2009|
|Digital Object Identifier (DOI):||10.2113/gsjfr.39.2.126|
|Appare nelle tipologie:||01 - Articolo su periodico|