Galeodinopsis cf. tiberiana ( Coppi, 1876 )

Garilli, Vittorio & Parrinello, Daniela, 2014, Taxonomy and palaeobiogeography of the Cenozoic Euro-Mediterranean rissoid gastropod Galeodinopsis and its relationship with close genera, Acta Palaeontologica Polonica 59 (2), pp. 379-406 : 398-400

Galeodinopsis cf. tiberiana ( Coppi, 1876)

Figs. 14D, E , 15.

Material studied.— 4 shells in MZPD (Mal 2033), ex AR, as Alvania sp. , from the Pliocene yellow fine sand cropping out in the right side of the Milicia River, Altavilla Milicia, Palermo, NW Sicily, Italy .

Description.—Shell conical, more elongate than typical Galeodinopsis tiberiana , reaching 3.2 mm in height and 2.05 mm in width. Ht/W ratio of about 1.5–1.6. Protoconch as for G. tiberiana . Teleoconch of little more than 3 convex whorls, with more-or-less marked subsutural ramp. Whorls sculptured by delicate to raised ribs, becoming obsolete to lacking on last whorl, crossed by finer spiral cords. Ribs weakly opisthocline or almost straight; 18–20 on penultimate whorl. Spiral cords quite narrow, numbering 3 on very early teleoconch, 4–6 and 9–11 on penultimate and last whorls, respectively. Each cord has pitted microsculpture, consisting of microscopic subcircular pores forming 4 spiral alignments. Pitted pattern formed by few flat threads connected by very short microscopic axial elements. Microsculpture between cords as for G. tiberiana . Last whorl inflated, well-expanded, comprising about 0.7 total shell height; two shells bear a single varix with angle of 180°. Aperture ovate, very rounded anteriorly, weakly angulated posteriorly, comprising 0.45–0.5 and 0.7 of total shell and last whorl heights, respectively. Outer lip very weakly

Fig. 15. Rissoid gastropod Galeodinopsis cf. tiberiana ( Coppi, 1876) , from the Late Zanclean–early Late Piacenzian, Pliocene of Altavilla Milicia, → Palermo, NW Sicily. A. Specimen ex AR, MZPD Mal 2033c with varix, in apertural (A 1), dorsal (A 2), and profile (A 3) views, protoconch (A 6), detail of protoconch 1 with trace of the netted sculpture (A 4), the Manzonia -like teleoconch pitted microsculpture on spiral cord (A 5). B. Specimen ex AR, MZPD Mal 2033d without varix in apertural (B

1

), dorsal (B

2

), and profile (B

3

) views, details of teleoconch sculpture (B

4

, B

5

) and microsculpture (B

6

), protoconch in profile view (B

7

). Note the variability of the outer lip: weakly sinuous and curved backward in the lower part (A

3

) to almost straight and opisthocline

B 3). Black and white arrows indicate the protoconch 1/protoconch 2 and protoconch/teleoconch boundaries, respectively. Scale bars: A 1 –A 3, B 1 –B 3, mm; A

6

, B

4

, B

5

, B

7,

100 μm; A

4

, A

5

, B

6

, 20 μm.

sinuous, opisthocline to almost straight; internally smooth, with thin rim on its edge; externally with marked varicose swelling, covered with spiral sculpture, with very narrow ridge on its base, towards aperture, forming weak double rim. Inner lip weakly curved, with very narrow columellar thickening, forming obsolete umbilical chink.

Remarks.—It is difficult to establish whether the material described here as Galeodinopsis cf. tiberiana really represents an extreme case of intraspecific variability. No similar morphs have been observed within the abundant material more than 200 shells) of G. tiberiana described above, and Coppi (1876) did not mention any intraspecific variation in the original description. Agatino Reitano (Tremestieri, Catania, Italy) provided this material as collected from unspecified layers from the Pliocene succession of Altavilla Milicia, in a lot containing also several shells indisputably belonging to G. tiberiana ( Fig. 14A ). Among these shells, three show a characteristic galeodiniform shape (Fig. 15A 1 –A 3, B 1 –B 3) strongly resembling species of Alvania , such as A. carinata Da Costa, 1778) and A. rosariae Garilli, 2008 (see Garilli 2008: figs. 1, 2, 4–8, 62–69); one shell ( Fig. 14D 1 –D 3) with more prominent sculpture might be regarded as somewhat intermediate between the galeodiniform shells and those typical of G. tiberiana .

Galeodinopsis cf. tiberiana (as illustrated in Fig. 15B 1 – B 3) resembles Rissoa moniziana Watson, 1873 (type of Moniziella Nordsieck, 1972), which has a somewhat atypical shell shape for Manzonia , but has the typical pitted surface of the genus (see Moolenbeek and Faber 1987c: figs. 58–60; Ponder 1985: figs. 102g and h). The two species share a strongly inflated shell and their sculptural pattern, with delicate, narrow spiral cords, a common character. However, M. moniziana has a paucispiral protoconch, indicating non-planktotrophic larval development, whereas G. cf. tiberiana has a multispiral protoconch indicating planktotrophic development. Furthermore, some specimens of G. cf. tiberiana bear varices on the last whorl, a typical Galeodinopsis character.

Figures

Fig. 14. Rissoid gastropods Galeodinopsis tiberiana (Coppi, 1876) (A–C, F, G) and G. cf. tiberiana (D, E), from the Neogene of the Mediterranean area. Altavilla Milicia, Palermo, NW Sicily, Late Zanclean–early Late Piacenzian, Pliocene (A, D, E); Stirone River, San Nicomede, Parma, N Italy, Pliocene (B); Rio Grizzaga sands, Gagliardella, Fogliano, Maranello, Modena, N Italy, Piacenzian, Pliocene (C, F, G). A. Specimen ex AR, MZPD Mal 2032, in apertural view, showing the typical G. tiberiana-morph. B. Specimen ex MF, MZPD Mal 2034 in profile view, showing the sinuous outer lip curved backwards in the lower part. C. Specimen ex MF, MZPD Mal 2035d, in apertural view, showing more axial and spiral elements. D. Specimen ex AR, MZPD Mal 2033a, in apertural (D 1), profile (D 2), and dorsal (D 3) views, somewhat transitional between specimen as in C and galeodiniform specimens as in E and in Fig. 15; protoconch in profile view (D 4). E. Galeodiniform specimen ex AR, MZPD Mal 2033b, in apertural (E 1) and profile (E 2) views, tentatively assigned to G. tiberiana. F. Specimen ex MF, MZPD Mal 2035e, showing detail of teleoconch sculpture with marked axial ribs. G. Specimen ex MF, MZPD Mal 2035f, showing protoconch in profile view. Black and white arrows indicate the protoconch 1/protoconch 2 and protoconch/teleoconch boundaries, respectively. Scale bars: A–C, D –D , E, 1 mm; D , F, G, 100 μm.

Fig. 1. Location of the study sites in the Euro-Mediterranean area. Open circles, studied from bibliographic sources; shaded circles, studied from museum/private collections.