Megaclavatula, Harzhauser & Landau & Janssen, 2022

Harzhauser, Mathias, Landau, Bernard & Janssen, Ronald, 2022, The Clavatulidae (Gastropoda, Conoidea) of the Miocene Paratethys Sea with considerations on fossil and extant Clavatulidae genera, Zootaxa 5123 (1), pp. 1-172 : 60-61

Genus Megaclavatula nov. gen.

Type species. Megaclavatula grunerti nov. sp., middle Miocene , Langhian (Badenian), Austria, Central Paratethys Sea .

Etymology. Combination of Mega - (Greek: large) and Clavatula .

Diagnosis. Medium to large sized, moderately slender fusiform, with high conical spire characterized by tripartite sculpture on early teleoconch whorls with two prominent, beaded adsutural cords and weaker, beaded mid-whorl cord. Subsutural collar coronate with pointed tubercles or spines. Base with weak sculpture; siphonal canal moderately long to long.

Description. Medium to large sized, moderately slender fusiform, with high conical spire. Protoconch not preserved. Early teleoconch whorls with prominent tripartite spiral sculpture comprising prominent, beaded subsutural cord. Slightly weaker, beaded cord in concave mid-whorl portion, and prominent beaded suprasutural cord. Beads in mid-whorl position and at the suprasutural cord form at ends of comma-shaped axial riblets. On later teleoconch whorls subsutural collar usually swollen, coronate, with small, pointed tubercles or trigonal spines (tubercles may be reduced in some species, e.g., M. evae ). Mid-whorl cord weakens, suprasutural cord weakens to subobsolete, bearing weak, wide-spaced tubercles. Secondary spiral threads may be present on spire whorls. Suture narrowly incised, weakly undulating. Last whorl typically ~ 55–60% of total height, attaining up to 65% in species with lower spire (e.g., M. pilleri nov. sp.). Weakly concave subsutural ramp, rounded periphery. Weakly delimited shoulder. Base moderately constricted, sculpture weak. Siphonal fasciole of medium length, weakly delimited. Aperture moderately wide, pyriform. Outer lip not thickened, smooth within. Anal sinus wide, moderately deep to deep, asymmetrically V-shaped, with apex below subsutural collar in deepest part of subsutural concavity. Siphonal canal moderately long to long, wide, often twisted and recurved, shallowly notched at tip. Columella straight to weakly twisted, smooth. Columellar and parietal callus thickened, sharply delimited, forming broad callus rim, without forming pseudoumbilicus.

Stratigraphic and geographic range. Middle Miocene (Langhian to Serravallian) of the Central Paratethys. Additional occurrences in the Miocene of the northeastern Atlantic and the Proto-Mediterranean Sea will need verification. Clavatula taurofusulata Sacco, 1890 and Clavatula subdepressa Sacco, 1890 , from the Burdigalian of the Colli Torinesi ( Italy), might be a Megaclavatula , but the early teleoconch whorls are poorly preserved and do not allow a clear identification. Similarly, Clavatula tortonica Peyrot, 1931 , might represent Megaclavatula , judging from the illustrations in Peyrot (1931), but we have not seen specimens. Pleurotoma asperulata Lamarck, 1822 , however, can clearly be placed in Megaclavatula based on early teleoconch sculpture.

Included species. Paratethys: Miocene: Megaclavatula grunerti nov. sp., Pleurotoma (Clavatula) amaliae Hoernes & Auinger, 1891 , Pleurotoma (Clavatula) antoniae Hoernes & Auinger, 1891 , Pleurotoma (Clavatula) evae Hoernes & Auinger, 1891 , Clavatula kowalewskii Bałuk, 2003 (= antoniae ), Pleurotoma laevigatum Eichwald, 1830 , Pleurotoma neudorfensis Schaffer, 1898 , Megaclavatula pilleri nov. sp., and Pleurotoma tuberculosa polonica Pusch, 1837 .

Proto-Mediterranean Sea: Miocene: Clavatula taurofusulata Sacco, 1890 , Clavatula subdepressa Sacco, 1890 , Pleurotoma ernesti Toula, 1901 . Northeastern Atlantic: Pleurotoma asperulata Lamarck, 1822 , Clavatula tortonica Peyrot, 1931 , Clavatula saubrigiana laurensii Peyrot, 1931 .

Discussion. Megaclavatula is reminiscent of Clavatula in general shape and the coronate spire, but differs distinctly in its tripartite early teleoconch sculpture and larger size. In addition, Megaclavatula species have a more constricted base and longer siphonal canal resulting in a more slender outline. A further difference is the deep U-shaped anal sinus of Clavatula , which contrasts with the moderately deep, broad V-shaped anal sinus of Megaclavatula .

Megaclavatula is mainly known so far from the Central Paratethys Sea and for most species from the ProtoMediterraean Sea and the northeastern Atlantic, included in Megaclavatula above, we have not seen early teleoconch whorls. Some morphologically similar species from the Serravallian of Turkey, described by Landau et al. (2013), display distinctly different early teleoconch morphology. Clavatula gracilis Erünal-Erentöz, 1958 , has two beaded adsutural spiral cords and Pleurotoma (Clavatula) francisci ( Toula, 1901) , develops a Perrona -like sculpture of opisthocline axial riblets (see Landau et al. 2013, pl. 70, figs 6–9).

Paleoenvironment. Coastal inner neritic to outer neritic environments.