Maja, Lamarck, 1801

Authors, The, 2014, Short communications, Natural History Sciences 1 (2), pp. 139-144 : 139

Maja cf. M. squinado (Herbst, 1788)

Figs. 1 , 2

Material and measurements: One incomplete right dactylus 18 mm long. (MSNM i27874).

Description: Elongate slender dactylus, finely granu- late dorsally, nearly straight, slightly curved downward distally; transverse section subrectangular proximally towards the articulation with the palm, and slightly compressed laterally, becoming subrounded towards the tip; unarmed occlusal margin with a median longitudinal finely serrate ridge, slightly convex and subtriangular in outline proximally, becoming straight dorsally and less marked towards the rounded pointed tip.

Discussion: Even though the studied specimen is poorly preserved, it shares morphological characters with the morphology of the dactylus of Maja Lamarck, 1801 , as follows: the dorsal granulation; the elongate nearly straight form, slightly curved downward distally, with subrounded transverse section; and the peculiar shape of the ridge on the cutting inner margin. Three extant species of Maja live in the Mediterranean Sea, Maja crispata Risso, 1827 , M. goltziana d’Oliviera, 1888 , and M. squinado (Herbst, 1788) . These species share similar dactyli but M. goltziana is an eurybathic species with very recent subtropical origin, inhabiting only the most south-eastern Mediterranean area without fossil records, whereas the more widespread M. crispata has never been recognised as fossil to date. So, the only fossil species known to date from the Cenozoic of the Mediterranean area is M. squinado , previously reported from different localities in Italy by complete specimens and loose dactyli. Indeed, the studied specimen could be compared with the right dactylus of an adult extant specimen of M. squinado , collected from the Adriatic Gulf (Mediterranean Sea) ( Fig. 2 ). Moreover, the specimen has been also compared with the two fossil dactyli having similar characters reported by Ristori (1891a, Pl. 1, fig. 28), from the Early Pleistocene of Monte Mario, Rome (central Italy), and by Varola (1981, Pl. 3, fig. 1) from the middle Pliocene of Rocca Vecchia (Lecce, southern Italy), both assigned to Maja squinado . Therefore, based on the above-mentioned characters and size, lacking comparative fossil records for the others two extant Mediterranean species, the studied specimen is tentatively compared and assigned to a juvenile individual of Maja squinado . This species has been previously reported in Italy from the Pliocene of Monte Mario (Roma), Rocca Vecchia (Salentina Peninsula, Puglia), Capo San Marco (Sardinia), Arda river (Emilia Romagna), Masserano (Piedmont) and La Serra quarry (Tuscany) (Meneghini, 1857; Ristori, 1891 a, b; Varola, 1981; Garassino & De Angeli, 2004; Pasini & Garassino, 2009; Garassino et al., 2012) and from the Pleistocene of Monte Pellegrino (Sicily) (Gemmellaro, 1914). The specimens reported from the Pliocene of Monte Mario (Rome) by Ristori (1891b) could be probably assigned to the Santernian (Early Pleistocene) (Cosentino et al., 2009). Substantially, this is the second report for the species along the northern borders of the paleo-Adriatic Gulf, increasing the scarce knowledge on the presence and distribution of the decapods crustacean fauna from this Mediterranean area during the Pliocene.

Figures

Fig. 1 - Maja cf. M. squinado, MSNM i27874, right dactylus. Scale bar 17 mm.

Fig. 2 - Extant Maja squinado, right cheliped; fine granulation of the dorsal surface of the dactylus (rectangular) and occlusal ridge, slightly convex and subtriangular in outline proximally (arrow) (adult female, Mediterranean Sea). Scale bar 120 mm.