Patella mahamensis Martín-González, 2018

Martín-González, Esther, Vera-Peláez, José Luis, Castillo, Carolina & Lozano-Francisco, M. Carmen, 2018, New fossil gastropod species (Mollusca: Gastropoda) from the upper Miocene of the Canary Islands (Spain), Zootaxa 4422 (2), pp. 191-218 : 200-202

Patella mahamensis Martín-González sp. nov.

Figure 5 G, H, I

1976 Patella cf. intermedia (Jeffreys) . Meco: pp. 78,83.

Type material. Holotype: Medium-size adult specimen with broken apex (L: 34.7 mm; W: 25.1 mm; H: 11.5 mm), record number TFMCFO-4605. Paratypes: Four samples, two of them very well conserved, with record numbers TFMCFO-4602 (L: 22.2 mm; W: 17.3 mm; H: 9.7 mm); TFMCFO-4 606 (L: 32 mm; W: 21.8; H: 13.2 mm); TFMCFO-4606b (L: 40.6 mm; W: 29.4 mm; H: 15.6 mm); TFMCFO-3527 (L: 22 mm; W: 14.9; H: 8.1 mm).

Type locality. Barranquillos Blancos ( Fuerteventura , Canary Islands). UTM 28 R 590819 m E 3156129 m N , 15 m asl. The level is composed of cemented biogenic sandstones with basaltic boulders, approximately 1 m thick. Tortonian dating, defined by the gastropod association described above. The paratypes are from Playa del Valle and Barranco del Cuervito, both in Fuerteventura.

Etymology. The species name derives from Maham, name of the subbmarine edifice common to the modern islands Lanzarote and Fuerteventura.

Description. Shell small (Lmax: 40.6 mm; Wmax: 29.4 mm; Hmax: 15.6 mm), slightly conical, longer than wide. Fragile apex, present in a single shell (although severely worn away), situated further towards anterior region. Very fluted sculpture (between 25 and 30 ribs) starting from the very apex, with three slightly pronounced ribs in the posterior region. Deep narrow flutes divide these ribs. All grooves display concentrically arranged nodules or scales. Growth lines barely visible. In ventral view, the shell profile is quadrangular and sinuous in contour. The mantle edge of the studied specimens leaves no impression.

Remarks. The shell of P. mahamensis sp. nov. is very similar to that of P. intermedia Murray, 1857 in Knapp , although the latter has a more rounded profile. Its radial ribs are more numerous and more evenly thick. However, in the fossil species P. mahamensis sp. nov. from the Canary Islands, the posterior ribs are more robust than the anterior ribs. Furthermore, the apex of P. intermedia is closer the center, whereas in P. mahamensis sp. nov., it is located towards the anterior end.

The fossil taxon P. mahamensis sp. nov. resembles P. vulgata Linnaeus, 1758 in shell shape and in the position of the apex closer to the anterior region; however, P. vulgata has a higher shell. Patella mahamensis sp. nov. has a more quadrangular profile with a rough margin, whereas the extant species P. vulgata displays an oval profile and a smooth margin. Finally, the main ribs are located near the center of the posterior region in the fossil species P. mahamensis sp. nov. while in P. vulgata , they are more equally distributed. Patella rustica Linnaeus, 1758 , another taxon similar to P. mahamensis sp. nov., is characterized by black tubercles in a spiral arrangement on the radial ribs. It is also higher and more conical than the fossil species P. mahamensis sp. nov., with an apex in a notably posterior position, a fine edge and a rounded profile. These same features differentiate P. mahamensis sp. nov. from P. piperata Gould, 1846 , a species closely related to P. vulgata , but distributed across the Canary Islands and Madeira.

Patella mahamensis sp. nov. resembles P. ulyssiponensis Röding, 1798 in some aspects. However, P. mahamensis sp. nov. is smaller, has a more rounded profile and an apex situated in the posterior region. Patella mahamensis sp. nov. shows groups of main ribs located close to each other with two intercalated moderatelydefined secondary ribs. However, in the extant species P. ulyssiponensis Röding, 1798 the main ribs are not well differentiated from the secondary ones and are arranged more towards the sides. Finally, Patella lugubris Gmelin, 1791 from Cape Verde has a more rounded profile, an anteriorly located apex and more evenly thick ribs than Patella mahamensis sp. nov. Table 3 contains the biometric variables and descriptive statistics for P. mahamensis sp. nov.

Distribution. Upper Miocene, Tortonian, Fuerteventura.

Figures

FIGURE 5. Patella tintina sp. nov., holotype, L: 100.6 mm; W: 85.2 mm; H: 50.1 mm; A. dorsal view; B. ventral view; C. lateral view. Patella maxoratensis sp. nov., holotype L: 93.6 mm; W: 80.5 mm; H: 42.9 mm; D. dorsal view; E. ventral view; F. lateral view. P. mahamensis sp. nov., holotype, L: 34.7 mm; W: 25.1 mm; H: 11.5 mm; G. dorsal view; H. ventral view.; I. lateral view. Scale 2 cm.