Ranina (Ranina) speciosa (von Münster, 1840)

Pasini, Giovanni & Garassino, Alessandro, 2017, A new raninoid crab (Decapoda, Brachyura, Raninidae) from the early Oligocene (late Rupelian) of Italy, Natural History Sciences 4 (1), pp. 87-96 : 89-90

Ranina (Ranina) speciosa (von Münster, 1840) - Allasinaz 1987: 529-535, Pl.1, figs.11-16, Pl. 2, figs. 1-6, Pl. 3, figs. 1-8.

? Ranina speciosa - Pasini & Garassino 2017: 57-59 ,

Fig. 12.

Diagnosis: as for the genus.

Etymology: the trivial name alludes to Ovada, close to which the fossiliferous sites are located.

Holotype: MPOM 290 .

Paratypes: MPOM701 , 1770 , 1776 , 1779 , 1780 , 17 MT.

Examined material and measurements: MPOM 4, 5, 10, 11, 13, 20, 21, 23, 171, 288, 290, 701, 1770, 1776, 1779, 1780, C1, C3, RMT, 17 MT, 39C, from different localities of the Ligure Piemontese Basin. In the complete specimens, Ctw ranges between 44 mm to 56 mm; Ctl ranges between 45.5 mm to 70 mm.

Geological age: late Rupelian (early Oligocene).

Type locality: Galanti (Cassinelle, Alessandria, Piedmont, NW Italy).

Description: Allasinaz (1987) reported several specimens originally assigned to Ranina (Ranina) speciosa (von Münster, 1840) . The original description in Italian language has never been translated. In this study we provide an updated description based upon the direct close review of the sample reported by Allasinaz (1987).

More (male) or less (female) ovate carapace slightly convex, longer than wide, tapering posteriorly, with maximum widest posteriorly to the base of the second anterolateral spine; wide orbito-frontal margin; frontal region, orbital, and anterolateral spines with marked sparse small pits, becoming smaller on the postfrontal regions; median and posterior regions with spiny tubercles frontally directed ( Fig. 2 ). Convex front wide; trifid rostrum depressed medially, bounded on either bottom side by symmetrical lateral divergent triangular rostral teeth serving as inner-orbital spines ( Fig. 2 ). Wide orbital margins with two teeth divided by two deep slightly divergent fissures; supraorbital tooth flat, forward directed with subtriangular anterior margin; postorbital tooth longer and larger, with three alternate points rounded distally; convex anterolateral margin, with two flat developed anterolateral spines; first anterolateral spine frontally directed and bifid, posterior margin slightly convex; second anterolateral spine wider and longer than the first one, elk horn-like shaped; upper margin nearly straight, strongly outward directed at an about 90° angle to the carapace middle line, tapering to a blunt point and with three (occasionally a fourth spine is present) triangular smaller, serrate and unequal pointed spines on the upper margin, more or less slender and elongate ( Fig. 2A ); carapace dorsal regions indistinct; weak or obsolete branchiocardiac grooves concave longitudinally C-shaped; posterolateral margins slightly convex, tapering posteriorly and with a thin ridge; nearly straight posterior margin. Sexual dimorphism present, with a wider carapace inflated anteriorly and anterolateral spines wider and longer in mature adult males, above all the first one, forward projected at level of the rostrum and orbital spines, forming an apparently nearly straight frontal outline margin ( Fig. 3A, B ). Sparse punctate, broad sternum winged; sternites 1-3 reduced, fused and domed frontally; sternite 4 lateral margins concave, laterally expanded and convex on the anterior margin; sternite 5 with a medial longitudinal depression; triangular in outline and narrowing posteriorly ( Figs. 3C , 4A ). Pleonal six somites sparsely granulate, rounded in female; s1-s5 similar in thickness, decreasing in wideness posteriorly, inflated longitudinally, forming a middle blunt rounded carena marked by two parallel lateral depressions; s1-s5 with pleurae rounded distally; convex dorsal margin, concave posteriorly, tapering gently distally to the narrow s6; pleon subtriangular shaped in male, with first somite subtrapezoidal, wider than others and narrowing to s6 ( Fig. 4C ). Elongate subrectangular, narrow oxystomatous 3 rd maxilliped nearly complete, preserving articulate exo- and endopodite. Endopodite nearly twice longer than exopodite ( Fig. 4B ). Chelae subtriangular wider distally, with teeth similar in shape and size; very flattened transversely high palm, granulated dorsally, with outer side having transverse sinuous subparallel wrinkled rims; palm proportionally larger than long in adult male; dorsal margin of the palm with a strong distal forward pointed spine near the articulation with the dactylus; lower margin of the palm bearing five alternate and pointed triangular spines saw-teeth like shaped forward directed, decreasing in size posteriorly; the anterior first longer; dactylus pointed, tip strongly curved downward, straight occlusal margin armed with a serrate rim of short teeth; triangular wide straight index, transverse to the axis of the palm, downward directed, armed with a rim of same size alternate teeth; reduced triangular carpus ending with two distal spines, ornamented with smooth transverse subparallel rims on the outer side; merus subtriangular, longer than carpus with a spine frontally directed on the outer margin; prominent scale lines at the mid dorsal outer side ( Fig. 5 A-C); ambulatory legs poorly preserved, flattened laterally, distal dactyli not preserved.

Intraspecific variability. The availability of a rich sample of specimens at different stages of growth, sizes, and preservation, allows us to point out the possible range of intraspecific variability in the main ‘proxy characters’ sensu Schweitzer (2003). The carapace shape changes proportionally in outline, more or less elongate or inflate anteriorly, with the ornamentation of the dorsal exoskeleton variable in size and arrangement, with more or less sparse granulations and distribution of the pits, based on the individual size and sex, but always well distinct between the postfrontal and the dorsal-posterior regions. The rostrum is always distinctly trifid in all individual stages. The width of the anterolateral spines may be individually more or less marked, with the first always bifid with the inner spine more or less developed and pointed, frontally directed, whereas the second one may have 3 to 4 accessory spines on the upper margin, alternate or adjacent, pointed, thin, and elongate or shorter triangular, and flat ( Fig. 6 ). Tip of the second spine pointed or blunt, always strongly outward directed, pointed or smooth nearly perpendicular to the carapace midline. The first anterolateral spine in larger mature males is strongly developed frontally and flattened, proportionally longer than the second anterolateral spine. Moreover, the P1 chelae are distinctly wider than long in mature larger specimens.

Figures

Fig. 2 - Alcespina ovadaensis n. gen., n. sp., carapace in dorsal view.A) holotype, MPOM 290 (Galanti, Cassinelle) (x 1.6). B) paratype, 17MT (Rio Volpina, Ponzone) (x 1.4). C) paratype, MPOM 1770 (Ciglione) (x 1.4). D) paratype, MPOM 1779 (Ponzone) (x 1.5).

Fig. 3 - Alcespina ovadaensis n. gen., n. sp, MPOM 1780 (Ciglione), mature male.A) dorsal view (natural size). B) anterolateral out- line (x 1). C) pleonal view (x 1.1).

Fig. 4 - Alcespina ovadaensis n. gen., n. s.p., RMT (Giusvalla).A)?female sternum (x1.8). B) 3rd maxilliped with endo- and exopodites (x 1.1). C) MPOM 39 (Ciglione), female somites (natural size).

Fig. 5 - Alcespina ovadaensis n. gen., n. sp. A) C3 (Ponzone), right chela (x 1.3). B) MPOM 740 (Ciglione), right and partial left chela (natural size). C) MPOM 1780, male chelae (x1.1).

Fig. 6 - Alcespina ovadaensis n. gen., n. sp., variability in the 2nd anterolateral spine. A) MPOM 1770 (x 2.5). B) MPOM 23 (x 1.7). C) MPOM 701 (x 2.2). D) MPOM 1776 (x 2.5).