Mangelia angulicosta, Scarponi & Bella & Dell’Angelo & Huntley & Sosso, 2016

Scarponi, Daniele, Bella, Giano Della, Dell’Angelo, Bruno, Huntley, John Warren & Sosso, Maurizio, 2016, Middle Miocene conoidean gastropods from western Ukraine (Paratethys): Integrative taxonomy, palaeoclimatogical and palaeobiogeographical implications, Acta Palaeontologica Polonica 61 (2), pp. 327-344 : 331-332

publication ID	https://doi.org/ 10.4202/app.00158.2015
persistent identifier	https://treatment.plazi.org/id/A8608798-FF80-FFB0-1CDC-7437FB6F445B
treatment provided by	Felipe
scientific name	Mangelia angulicosta
status	sp. nov.

Treatment

Mangelia angulicosta View in CoL sp. nov.

Figs. 3A View Fig , 4 View Fig , 5A View Fig ; SOM 1: fig. 3A, SOM 2.

Etymology: From Latin angulus, angle and costa, rib; named after the distinctive, sharply angulated profile of its axial ribs.

Type material: Holotype, MGGC-24505 , adult, well-preserved shell . Paratypes, MGGC-24506 /1–14 from the type locality (SOM 2) .

Type locality: Varovtsi , Ukraine .

Type horizon: Massive, white sandstone of the Pidhirtsi Beds, early Serravallian (~14.0−12.7 Ma).

Material.— Six topotype specimens from Varovtsi: IGS- NANU-B-I-1/2015 (1 sh), MGPT-PU135044 (1 sh), NHMW-2015 /0404/0001 (2 shs), and ZISP-62073 (2 shs) .

Diagnosis.—A small Mangelia species (shell lengthm 5.1mm, sd 0.7 mm; shell widthm 2.2 mm, sd 0.2 mm), characterised by a multispiral protoconch (lengthm 0.52 mm, sd 0.04 mm; widthm 0.49 mm, sd 0.03 mm), a relatively short spire (0.34 shell lengthm, sd 0.02) and a slightly bent columellar lip. Teleoconch sculpture of strongly angulated, narrow and prominent ribs (max 10 on the second whorl) along with dense, thin and, in the last whorl, fairly uniform, flat topped spiral elements.

Description.—Shell small-sized, fusiform, spire turreted 0.34 shell lengthm, sd 0.02); last whorl narrow (2.2 mm, sd 0.2 mm), elongated (3.3 mm, sd 0.4 mm). Protoconch dome-shaped, of 1.9 convex whorls (sd 0.1 wh); nucleus medium-sized, smooth as remaining whorls except the final quarter, where 3−5 weak cordlets override comma-shaped, thin, slightly opisthocline, axial riblets strengthening at the protoconch-teleoconch boundary. Teleoconchm of 4.2 whorls sd 0.4 wh), angulated in profile, with noticeable axials and subdued spiral sculpture; suture undulating.Axials of narrow, well developed, slightly opisthocline, angulated, far apart ribs typically 9 on second whorl), extending across sutures on spiral whorls, until the base of the last whorl. Spiral sculpture dense, fairly uniform, made of thin, flat-topped threads separated by incised lines; on early whorls, a few (usually 3 on second whorl) thin spiral cords also present. Growth lines occasionally evident. Aperture moderately narrow, sub-rectangular (lengthm 2.2 mm, sd 0.3 mm), siphonal canal short. Outer lip thin-edged, slightly convex in profile, internally thickened; anal sinus C-shaped; columellar lip slightly bent.

Remarks.— Mangelia angulicosta sp. nov. is similar to Mangelia atlantica Pallary, 1920 , an extant Atlantic− Mediterranean taxon (SOM 1: fig. 4A, SOM 2), that is currently considered a synonym (or subspecies) of Mangelia costata Pennant, 1777 ) ( Scarponi and Della Bella 2010; WoRMs 2014 and references therein). In particular, the two species share comparable shell dimensions, teleoconch sculpture, and morphology of the aperture and sinuses (e.g., SOM 1: fig. 3A vs. fig. 4A). Quantitative comparison of the previously mentioned teleoconch parameters support a strong overlap between the new species and M. costata (e.g., shell lengthm 5.1 vs. 4.8 mm, respectively; p = 0.29) as well as comparable coefficients of intraspecific variation (for further details see Fig. 2 View Fig , Table 1, SOM 3). However, M. costata is characterised (and distinguishable from M. angulicosta ) by its: (i) smaller number of teleoconch whorls (i.e., 3.2 vs. 4.2) at comparable shell length (see above); (ii) less numerous teleoconch ribs (average on second whorl 8.4 vs. 9.1, p << 0.01; (iii) bigger protoconch (lengthm 0.76 vs. 0.52, p << 0.01; widthm 0.66 vs. 0.49 mm, p << 0.01) and higher number of protoconch whorls (2.8 vs. 1.9, p << 0.01; further details in Fig. 2 View Fig , Table 1, SOM 3). Furthermore, with respect to M. costata , the axial ribs in M. angulicosta are sharply angulated at approximately 2/3 of the whorl, then proceed straight toward the adapical suture, giving the spire its characteristic angulated profile ( Fig. 3A View Fig vs. SOM 1: fig. 4A).