Turritellinella, Harzhauser & Landau, 2019

Harzhauser, Mathias & Landau, Bernard, 2019, Turritellidae (Gastropoda) of the Miocene Paratethys Sea with considerations about turritellid genera, Zootaxa 4681 (1), pp. 1-136 : 74-75

Genus Turritellinella new gen.

Type species: Turbo tricarinatus Brocchi, 1814 . Pliocene , Italy .

Diagnosis. Small to medium sized, turriculate shells of 15–20 convex to moderately convex teleoconch whorls. Mammilate protoconch consisting of 2.5 smooth, strongly convex whorls of c. 250 μm diameter. First neanic whorl tricostate with very prominent B spiral cord, A and C cords much weaker; order of appearance B-C-A (almost simultaneously). Spiral sculpture extremely variable consisting basically of three primary cords and variable numbers of secondary and tertiary cords; primary cords often distinctly weakening during ontogeny and secondary/tertiary cords rivaling primary ones on late teleoconch whorls. Spiral cords weakly papillate on early whorls. Growth lines prominent especially in interspaces between spiral sculpture. Lateral sinus moderately steep; deep to moderately deep with well-defined vertex; faint adapical and abapical inflection points ( Fig. 6 Ai). Base weakly convex. Aperture subcircular to subquadrate; inner lip thin, narrowly reflected.

Etymology. Referring to Turritella and the small size of the species included in the new genus.

Included species. Turbo tricarinatus Brocchi, 1814 (Pliocene, Italy) [= T. tricarinata Brocchi, 1814 ], Turritella communis Risso, 1826 (Recent, Mediterranean Sea) [= T. tricarinata Brocchi, 1814 ], Turritella communis ariesensis Fontannes, 1897 (Pliocene, France) [= T. tricarinata Brocchi, 1814 ], Turritella communis pliorecens Scalia, 1900 [= T. tricarinata Brocchi, 1814 ], Turritella tricarinata percincta Sacco, 1895 (Pliocene, Italy) [= T. tricarinata Brocchi, 1814 ], Turritella tricarinata laevicincta Sacco, 1895 (Pliocene, Italy) [= T. tricarinata Brocchi, 1814 ], Turritella tricarinata miofasciata Sacco, 1895 (late Miocene, Italy) [= T. tricarinata Brocchi, 1814 ], Turritella tricarinata pseudocarinata Sacco, 1895 (Pliocene, Italy), [= T. tricarinata Brocchi, 1814 ], Turritella torinensis d’Orbigny, 1852 (Pliocene, Italy) [= T. tricarinata Brocchi, 1814 ], Turritella communis subuliformis Boettger, 1907 (middle Miocene, Badenian, Central Paratethys).

Remarks. Landau et al. (2004) synonymized the fossil Turbo tricarinatus Brocchi, 1814 with the extant Turritella communis Risso, 1826 (based on Pliocene populations from southern Spain) and doubted that these taxa (including pliorecens) can be treated as chronosubspecies, because all morphotypes may co-occur in Pliocene and Recent assemblages. This view is supported by a comparison of the protoconchs of T. tricarinata and T. communis , which are nearly identical (see Bernasconi 1990: 32, pl. 1, figs 1–2 versus Fretter & Graham 1981: 287, fig. 216). In both morphotypes, the first neanic whorl is tricostate with a very prominent B spiral cord and much weaker B and C cords. Therefore, we follow the concept of Landau et al. (2014) and treat all these taxa, including the ‘varieties’ described by Sacco (1895) from the Miocene and Pliocene of Italy, as T. tricarinata .

Stratigraphic and geographic range. The oldest record of T. tricarinata is mentioned by Sacco (1895) from the Oligocene of Dego ( Italy), which is most probably based on misidentifications. Records that might be more reliable are listed by Sacco (1895) from the early Miocene (Burdigalian) of the Torino Hills ( Italy), but these will need confirmation. Turritellinella subuliformis ( Boettger, 1907) , from the middle Miocene of Romania, is the earliest verified occurrence of the genus. The type species T. tricarinata appeared at least during the late Miocene, reported from Stazzano and San Agata in Italy ( Sacco 1895), and became abundant in the Mediterranean Sea during the Pliocene when it reached also the Atlantic. Pleistocene occurrences are documented by Caprotti (1975) from the central Mediterranean. The modern distribution of T. tricarinata ranges in the Eastern Atlantic from North Africa to Norway ( Fretter & Graham 1981; Gofas 2011) and covers the entire Mediterranean Sea and parts of the Black Sea ( Poppe & Goto 1991; Snigirov et al. 2013).

Paleoenvironment. Recent specimens of Turritellinella tricarinata inhabit soft bottom environments in 10–200 m water depth ( Fretter & Graham 1981; Gofas 2011). The Miocene T. subuliformis seems to have preferred similar habitats, based on its occurrence in basinal clays.

Discussion. The type species of Turritellinella and all its junior synonyms have been listed as Turritella Lamarck, 1799 by all authors (e.g. Sacco 1895; Caprotti 1975; Gude 1981; Bernasconi 1990; Landau et al. 2004; Gofas 2011). Cossmann (1912: 111, 113) treated Turritella communis Risso, 1826 and Turritella tricarinata ( Brocchi, 1814) as Turritella sensu stricto, which was followed by Guillaume (1925: 282). As Marwick (1957) was mainly focusing on type species, he did not discuss this species at all. A relationship with Turritella Lamarck, 1799 , however, is highly unlikely. Aside from the distinctly smaller size of all Turritellinella species, the lateral sinus differs considerably from the wide and simple lateral sinus of Turritella . Moreover, the order of appearance of primary spiral cords is B-A-C in Turritella but B-C-A in Turritellinella . This formula differs also from Oligodia and Peyrotia (B-D), Ptychidia (B-A-C) and Zaria and Haustator (C-B-A). Only Helminthia has the same order of appearance of primary spirals but differs in its larger size, less convex whorls and less incised suture, the nearly flat base and the characteristic secondary spiral sculpture covering the prominent primary cords.

Figures

FIGURE 6. Growth line traces of Turritellidae species based on own data; bold: type species of genera; black: Paratethyan species; asterisk: non-Paratethyan species (unknown basal sinuses are left blank).