Mathilda praeclara Boettger, 1902

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

Mathilda praeclara Boettger, 1902

Figs 24B 1 –B 2

* Mathilda praeclara n. sp. — Boettger 1902: 155.

Mathilda praeclara Boettger — Cossmann 1912: 10.

Mathilda praeclara Boettger —Zilch 1934: 216, pl. 7, fig. 10.

Mathilda praeclara Boettger, 1901 — Bałuk 2006: 196: pl. 7, fig. 4.

? non Mathilda praeclara —Zunino & Pavia 2009: 360.

Type material. Holotype: SMF 372690 (XII 2491a), SL: 4.6 mm, MD: 2.3 mm, Senckenberg Museum, Frankfurt/ Main, Germany, Coşteiu de Sus ( Romania), illustrated in Zilch (1934: pl. 7, fig. 10), Figs 24B 1 –B 2 .

Revised description. Small, robust, moderately stout conical shell; apical angle 26°. Protoconch multispiral, of about 2.5 smooth whorls, heterostrophic, nucleus and about half of protoconch not exposed, tilted at angle of about 140°. Teleoconch of four angulated whorls with moderately incised suture. First teleoconch whorl with primary spiral cords: S1 moderately prominent; S2 prominent forming keel, coinciding with angulated periphery; S3 narrowest, weakly tuberculate close above abapical suture. On third cord weak spiral thread appears on slightly concave sutural ramp, and a further one, later two on last whorl between S1 and S2. Sutural ramp widening abapically. Axial sculpture of c. 28 prominent, narrow, straight lamellae, forming cancellate pattern, with small tubercles developed at intersections; axials weakening on last whorl. Base delimited by two weak peribasal cords, rapidly contracting, flattened. Umbilicus reduced to narrow chink, delimited by low periumbilical cord. Aperture subpentagonal, moderately wide, anteriorly slightly angulated. Columella straight. Columellar callus forming narrow rim persisting on parietal area. Outer lip thin. About four spiral lirae deep in aperture.

Discussion. Mathilda clara Boettger, 1902 , M. praeclara Boettger, 1902 are clearly closely related species differing from other Mathilda species in having a small umbilical chink delimited by a low periumbilical cord. Mathilda margaritula Semper, 1865 also has a weak periumbilical cord, but is quite different in sculpture. This feature is therefore not considered important a generic level. Apart from the differences between the two discussed under M. clara , M. praeclara has lirae within the outer lip. To our knowledge, this is the first time that lirae are documented from Mathildidae . The importance of these lirae is unknown. The sculpture of Mathilda praeclara is close to that of M. inhereditaria Lozouet, 1999 , from the Chattian of the Aquitaine Basin. Both species differ mainly in the slender profile of M. inhereditaria .

Mathilda preaclara was listed but not described or figured by Zunino & Pavia (2009) from the Burdigalian of the Colli Torinesi ( Italy). In view of the very low number of species shared between these two Miocene basins following this revision, this identification will need verification, and is provisionally excluded from the distribution.

Paleoenvironment. Unknown; probably middle to outer neritic.

Distribution. Only known from the Langhian equivalent of the Badenian in the Central Paratethys Sea.

Central Paratethys Sea. Middle Miocene (Badenian): Korytnica Basin: Korytnica ( Poland) ( Bałuk 2006); Făget Basin: Coşteiu de Sus (Semper 1865; Boettger 1902).

Figures

FIGURE 1. Descriptive terms used in descriptions of Architectonicidae (modified from Bieler 1993).

FIGURE 2. Whorl cross-sections of Architectonicidae genera. All modified after Bieler (1993) except for Simplexollata, Basisulcata and Ammotectonica. Solatisonax? refers to Solatisonax? kostejana (Boettger, 1907), Bold genera are represented in the Paratethys Sea. SSC: subsutural cord, MC: mid cord(s), UPC: upper peripheral cord, LPC: lower peripheral cord, IPC: infraperipheral cord; UC: umbilical crenae; PUC: proxumbilical cord.

FIGURE 24 A1–A2. Mathilda clara Boettger, 1902, lectotype, SMF 372692, Coşteiu de Sus (Romania). B1–B2. Mathilda praeclara Boettger, 1902, holotype, SMF 372690, Coşteiu de Sus (Romania).