Fimbriatella Sacco, 1895

Harzhauser, Mathias & Landau, Bernard, 2023, The Architectonicidae and Mathildidae (Gastropoda, Heterobranchia) of the Miocene Paratethys Sea-victims of the Miocene Climatic Transition, Zootaxa 5370 (1), pp. 1-74 : 53-54

Genus Fimbriatella Sacco, 1895

Type species. Cerithium fimbriatum Michelotti, 1847 ; original designation by Sacco (1985: 36). Miocene, Italy .

Note that Sacco (1895: 36 erroneously wrote “ F. fimbriatella (Micht.) ” but corrected this mistake in Sacco (1896: 81) (see also Bieler 1995: 600).

Original diagnosis. “ La specie di questo Gruppo distinguonsi dale vere Mathilda per la forma più conica, gli anfratti fortemente angulosi, la bocca meno rotunda, subcaudata, ecc.” [species of this group are distinguished from real Mathilda by its more conical shell, the strongly angular whorls, the less circular aperture, [its] subcaudate [base], etc.] (Sacco 1895: 36).

Revised diagnosis. Medium-sized to large, solid, broad turritelliform with strongly angled whorls with concave profile. Protoconch heterostrophic Sculpture on first teleoconch whorl of three primary spiral cords: S1 moderately developed, placed abutting upper suture; S2 placed mid-whorl weakest; S3 strongest, placed close above abapical suture. Later whorls with carinate S3, coinciding with periphery. Secondary spiral cords may appear between suture and S1, and between S1 and S2. Axial sculpture of close-set, narrow, arcuate axial lamellae that overrun cords forming tubercles at intersections. Aperture subcircular, anteriorly slightly angulated. Columella slightly twisted. Columellar callus indistinct. No parietal callus. Siphonal canal short, wide. Differing from Mathilda in it is weak S2, concave whorl profile and carinate S3, which coincides with periphery.

Discussion. Fimbriatella was synonymized with Mathilda by Bieler (1995: 600) but in our opinion the different mode of sculpture formation and the concave whorl profile justify a separation of Fimbriatella . Extant Mathilda species such as Mathilda cf. quinquelirata in Bieler (1995) and Mathilda fusca (Okutani & Habe, 1981) differ in that the periphery is formed by S2, which migrates towards the abapical suture during ontogeny giving them a ‘ Fibriatella -like’ profile, but their periphery is at S2, and therefore they should be placed in Mathilda .