The Lower Pliocene marine gastropods of Santa Maria Island, Azores: Taxonomy and palaeobiogeographic implications Author Sacchetti, Claudia 0000-0002-3225-3139 claudiasacc@icloud.com Author Landau, Bernard 0000-0002-7768-8494 bernardmlandau@gmail.com Author Ávila, Sérgio P. 0000-0002-3225-3139 claudiasacc@icloud.com text Zootaxa 2023 2023-05-24 5295 1 1 150 http://dx.doi.org/10.11646/zootaxa.5295.1.1 journal article 53396 10.11646/zootaxa.5295.1.1 82286fdc-a858-447c-9980-da2e8985d19c 1175-5326 7965273 F3A52660-70B8-439F-A7A0-F45ADC975EA5 Hipponix sulcatus ( Borson, 1820 ) Plate 2 G 1 -G 3 * Patella sulcata Borson 1820: 185 . Hipponyx [ sic ] granulatus de Basterot 1825: 62 , pl. 4, fig. 14. Pileopsis granulosa Grateloup 1836: 279 , pl. 1, figs. 29-30. Pileopsis granulosa Grat. —Grateloup 1847: 1, figs. 29-30. Hipponyx sulcatus Borson — Mayer 1864: 54 . Gadinia sulcata (Borson) —Cossmann 1895: 145, pl. 6, figs. 20-22. Amalthea? sulcata (Bors.) —Sacco 1895: 44, pl. 5, fig. 24. Amalthea? sulcata var. pyramidata Sacco 1895: 45 , pl. 5, fig. 25. Amalthea? sulcata var. subcrenulata Sacco 1895: 45 , pl. 5, fig. 26. Amalthea? sulcata var. plioparva Sacco 1895: 45 , pl. 5, fig. 27. Amalthea? sulcata var. dertonatulina Sacco 1895: 45 , pl. 5, fig. 28. Hipponyx [ sic ] sulcatus (Borson) —Cossmann & Peyrot 1919: 522, pl. 14, fig. 64, pl. 15, figs. 12-15. Hipponyx [ sic ] sulcatus (Borson) — Lozouet et al. 2001: 40 , pl. 15, fig. 3. non Amalthea sulcata Borson, 1820 — Glibert 1949: 20 , pl. 12, fig. 13 (= Hipponix helveticus Cossmann & Peyrot, 1919 ). non Hipponix sulcatus ( Borson, 1820 ) — Chirli & Linse 2011: 93 , pl. 27, fig. 3. [= Hipponix bistriatus ( Grateloup, 1827 ) ]. Santa Maria material examined. Maximum height 5.3 mm, diameter 14.0 mm. DBUA-F 937-1 (1), DBUA-F 469- B (1), Ponta do Castelo, Santa Maria Island, Azores , Touril Complex, Lower Pliocene. Description. Shell medium sized, solid, relatively depressed, patelliform, with an elliptical profile. Protoconch eroded in all specimens. Apex placed just posterior to center. Dorsal sculpture of rounded ribs ( 74 in Azorean specimen) of equal strength, cut by numerous concentric growth lines, making ribs tuberculose. Ventral aspect smooth, except for horse-shoe shaped muscle scar. Discussion. A single well-preserved Hipponix specimen from the Azores is identical to specimens of Hipponix sulcatus ( Borson, 1820 ) , which was originally described from the Lower-Middle Miocene of the Colli Torinesi, Italy (NHMW collection). Cossmann & Peyrot (1919: 524) correctly noted that the Atlantic Lower-Middle Miocene Aquitanian-Langhian specimens from the Aquitaine Basin of France were identical to those from the Colli Torinesi (see also Lozouet et al . 2001: 40 , pl. 15, fig. 3). These specimens are characterised by having coarse radial ribs strengthening toward the periphery and an apex placed on the dorsum just posterior to center. Glibert (1959: 201), considered the Atlantic Middle Miocene Langhian specimens from the Loire Basin conspecific.Numerous specimens at hand from several localities in the Loire Basin (Ferrière-Larçon, Pauvrelay, Mathelan: NHMW collection) suggests this is not correct. Apart from being smaller, as noted by Cossmann & Peyrot (1919) and Glibert (1959), the radial sculpture is finer, and the apex is more pointed and placed far more posteriorly, and in fully adult specimen, overhangs the posterior margin. These differences were already noted by Cossmann & Peyrot (1919: 324), who erected the variety helvetica for the Loire Basin form. We agree with Peyrot (1938: 88) , in separating these smaller specimens, and elevate the name to full-species rank: Hipponix helveticus Cossman & Peyrot, 1919 . Although a predominantly Lower and Middle Miocene Atlantic species, Sacco (1895), reported it from the Upper Miocene of Italy and the single Lower Pliocene Italian locality of Bussana Vecchia, Imperia, Liguria . We are not aware of any subsequent Pliocene references to the species, and it is not present in the Pliocene of the Estepona Basin. Hipponix bistriatus ( Grateloup, 1827 ) , which does occur in the Estepona Basin deposit ( Landau et al. 2004a: 69 , pl. 18, fig. 2), differs in being less depressed, in having the apex overhanging the posterior margin, and finer axial sculpture consisting of ribs of alternating strength. Hipponix explicatus Landau, Marquet & Grigis, 2004a , also from the Estepona assemblages, is characterised by a peculiar shell without axial sculpture and a strongly disjunct last whorl, quiet unlike H. sulcatus , H. bistriatus or H. helveticus . Chirli & Linse (2011: 93 , pl. 27, fig.3) illustrated a specimen from the Pleistocene of Rhodes Island as H. sulcatus . The specimen illustrated is far less depressed than usual for the species, the apex is placed at the posterior margin and there is a secondary rib between each primary. It probably represents H. bistriatus . Hipponix sulcatus seems to have survived into the early Pliocene in the Mediterranean, now known from a single locality in Italy (Sacco 1895), and in the Atlantic, in the Azores (this paper). These records probably represent relict populations that did not survive the cooling events at the end of MPPMU1. Distribution. Lower Miocene: Atlantic (Aquitanian and Burdigalian), Aquitaine Basin, France (de Basterot 1825 ; Grateloup 1836 , 1847; Cossmann & Peyrot 1919; Lozouet et al. 2001 ); central Proto-Mediterranean, Colli Torinesi, Italy ( Borson 1820 ; Sacco 1895). Upper Miocene: central Proto-Mediterannean, Italy (Sacco 1895). Lower Pliocene: Atlantic, Santa Maria Island, Azores ( Mayer 1864 ); central Mediterranean, Italy (Sacco 1895).