Patella maxoratensis Martín-González & Vera-Peláez

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: 197-200

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Patella maxoratensis Martín-González & Vera-Peláez

sp. nov.

Patella maxoratensis Martín-González & Vera-Peláez  sp. nov.

Figure 5 D, E, F View Figure

Type material. Holotype: complete shell of a large adult, perfectly preserved (L: 93.6 mm; W: 80.5 mm; H: 42.8 mm), record number TFMCFO-3437. Paratype: five well-preserved specimens: TFMCFO-4597a (L: 104 mm; A: 91.3 mm; H: 50.7 mm); TFMCFO-4597b (L: 86 mm; A: 71.8 mm; H: 43.5 mm); TFMCFO-3722 (L: 63.7 mm; A: 56.5 mm; H: 26.2 mm); TFMCFO-4594 (L: 48.9 mm; A: 35 mm; H: 18.1 mm); TFMCFO-6107 (L: 24.3 mm; A: 18.4 mm; H: 7.7 mm).

Other material examined. Two specimens from Lanzarote (TFMCFO-3836, Punta Gorda), 21 from Fuerteventura (TFMCFO-3463, TFMCFO- 6503, Playa del Águila; TFMCFO-3486, Agua Ovejas; TFMCFO- 3535, Caletones Mansos; TFMCFO-3630, La Bonancita; TFMCFO-3718, Punta del Viento; TFMCFO-3722, TFMCFO-4594, TFMCFO-4597, TFMCFO-4600, TFMCFO- 6107, Aljibe de la Cueva; TFMCFO-3437, TFMCFO- 4603, TFMCFO-4604, TFMCFO-5991, TFMCFO-6404, TFMCFO-6555, Bajas Amarillas; TFMCFO- 4606, Playa del Valle; TFMCFO-4607, Barranco León) and one from Gran Canaria (TFMCFO-6336, La Esfinge) have been examined. The biometric and statistical variables of P. maxoratensis  sp. nov. are displayed in Table 2.

Type locality. Bajas Amarillas (Fuerteventura, Canary Islands). UTM 28 R 593643 m E 3161892 m N, 10 m asl  . The level is composed of cemented bioclastic sandstones, 1 m in thickness. Tortonian dating defined by the gastropod association described above. The paratypes are from Aljibe de la Cueva, in the north of Fuerteventura.  

Etymology. The specific name derives from Maxorata, the name given to the island of Fuerteventura by its aboriginal population.

Description. Shell cap-shaped, large (Lmax: 104 mm; Wmax: 91.3 mm; Hmax: 50.7 mm), narrowly conical, slightly longer than wide, with many strong axial ribs radially arranged from apex to base. Apex situated at the geometric center of the shell. Fourteen primaries, well-defined radial ribs; primary ribs slowly increasing in width during ontogeny (widening from apex towards base). Four primary ribs are directed towards the posterior area. Also starting from the apex, there are one or two finer secondary ribs between each pair of primary ribs. During ontogeny, two additional tertiary ribs are visible between each pair of secondary ribs. As consequence, the adult shell is strongly fluted axially by numerous radial ribs (between 50–60). The primary ribs have by four or five finer ribs on their surface. As a result, a total of approximately 90 fine radial ribs are present at the shell margin. Most ribs are interrupted by axially elongated nodules or scales and are crossed by well-defined growth lines, which circumscribe a circular, slightly sinuous contour. The base displays a sinuous outline with four rounded edges at position of ribs, widely separated posteriorly. This base contour traces an oval-pentagonal outline with four tips in the posterior region and one at the anterior end, with a sinuous contour across the whole perimeter. In ventral view, no growth lines are visible. Impression of the mantle edge shows a dark broad band at half of the height of the shell, open anteriorly. Shell color has not been conserved; the holotype is black, probably due to taphonomic processes.

Remarks. Like Patella tintina  sp. nov., this species differs from P. ambroggii Lecointre, 1952  in its much higher number of finer ribs, a centrally positioned apex and greater size. Patella maxoratensis  sp. nov. can be separated from P. tintina  sp. nov. by its apex located in a central, instead of a posterior, position; its greater number of radial, finer ribs; and its nodules or scales along the whole length of the radial ribs, not present in P. tintina  sp. nov. In addition, the shell is more conical, and the outline is oval-pentagonal but never star-shaped, whereas in P. tintina  sp. nov. the outline is star-shaped with strongly protruding ribs, displaying radial fluting on the inner side where the primary ribs are. Such fluting is not present in Patella maxoratensis  sp. nov. The juvenile shell stages are similar in both species, which suggests they might share a common evolutionary origin. Patella maxoratensis  sp. nov. differs from other Miocene Patella  species in both, size and shell morphology. The large South African limpet Cymbula oculus ( Born, 1778)  closely resembles P. maxoratensis  sp. nov. However, Cymbula oculus  differs in having finer radial ribs, in having a flatter shell profile and in having five main ribs towards the posterior part. The South African species Cymbula granatina ( Linnaeus, 1758)  and Scutellastra barbara ( Linnaeus, 1758)  both differ in their rib layout and in their more rounded base contour. The South African Scutellastra granularis ( Linnaeus, 1758)  displays small scales on the ribs, its shell profile is rounded and its ribs are less marked. The Mediterranean limpet, P. ferruginea Gmelin, 1791  can be distinguished from P. maxoratensis  sp. nov. by the regular layout of ribs, which are wider and stronger. Patella rustica Linnaeus, 1758  , also from the Mediterranean, shares the ornamentation with nodules on the radial ribs, but differs in its shell size and in having a rounded profile. Patella maxoratensis  sp. nov. resembles P. piperata  in having axially elongated nodes on the radial ribs and in having a narrowly conical shell shape. However, P. piperata  is much smaller and has a circular-oval base contour instead of a sinuous-pentagonal like that of the fossil species P. maxoratensis  sp. nov. Additionally, Patella maxoratensis  has a sinuous contour similar to that of P. ulyssiponensis  , whereas the extant species displays a larger number of ribs, which are closer to each other and with an irregular appearance. The latter is also less conical, with the apex toward the posterior area.

Distribution. Upper Miocene, Tortonian: Fuerteventura, Lanzarote and Gran Canaria.