Alcespina, Pasini & Garassino, 2017

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 : 88-89

Genus Alcespina nov.

Diagnosis: carapace ovate, wide fronto-orbital margin convex; trifid pointed rostrum, depressed medially; first anterolateral spine bifid, forward directed, parallel to the middle longitudinal axis; second wide anterolateral spine pointed, flat, strongly outward directed, forming by the straight upper margin, an angle around 90° to the carapace middle line, with triangular unequal serrate spines (3-4) on the upper margin; dorsal regions indistinct.

Type species: Alcespina ovadaensis n. sp.

Included fossil species: Alcespina berglundi ( Squires & Demetrion, 1992) n. comb. (this paper).

Etymology: from Alces (elk), and spina (spine), alluding to the second anterolateral spines shape, remembering elk horns.

Geological range: early Eocene – early Oligocene.

Palaeogeographic distribution: the genus is reported from the NE Pacific [ Alcespina berglundi ( Squires & Demetrion, 1992) n. comb.] and Mediterranean area ( A. ovadensis n. sp.); probably also reported in the NE Atlantic (Biarritz, SE France) with R. bouilleana A. Milne Edwards, 1872 .

Description: as for type species.

Discussion: we justify the description of the new genus, in having a unique combination of distinctive characters within the Ranininae , different from the other genera ascribed to the subfamily, as follows:

- Lophoranina Fabiani, 1910 , has distinct carapace surface with typical transverse tegulate rims, usually parallel to one other, two anterolateral spines bifid, broad sternum with C-shaped concave lateral margins.

- Lophoraninella Glaessner, 1936 , has carapace with short scabrous ornamentation in anterior third, serrate transverse rimmed ornamentation on remainder of carapace.

- Ranina Lamarck, 1801 , has triangular rostrum, smaller orbital spines, two anterolateral palmate spines that are respectively bifid or trifid in mature individuals, both ante- rolaterally directed, broad sternum at level of sternites 1-3.

- Raninella A. Milne Edwards, 1862 , has carapace widest about half the distance posteriorly, carapace surface covered by densely spaced inclined nodes, anterolateral margin generally with two flattened spines triangular or more narrow, sternum lanceolate distally, narrow anteriorly and wider at level of the last posterior sternites.

- Remyranina Schweitzer & Feldmann, 2010 , has expanded, moderately broad fronto-orbital margin, ovoid carapace slightly larger than wide, and carapace ornamentation granular in anterior half and strongly terraced in posterior half.

- Vegaranina Van Bakel, Guinot, Artal, Fraaije & Jagt, 2012 , has anterolateral margin with three triangular spines, carapace ornamented with developed broadly spaced transverse terraces.

For detailed diagnosis see Karasawa et al. (2014).