Tethyranina, Pasini & Garassino, 2018

Pasini, Giovanni & Garassino, Alessandro, 2018, Critical review of fossil record of Ranina Lamarck, 1801 (Decapoda, Brachyura, Raninidae), with description of Tethyranina n. gen., Natural History Sciences 5 (2), pp. 3-12 : 8

Genus Tethyranina nov.

Diagnosis: Carapace ovate, tapering posteriorly; wide fronto-orbital margin convex; dorsal surface with triangular tubercles-spines randomly arranged; pointed triangular rostrum; triangular orbital spine; subtriangular supraorbital spine flattened, forward directed with slightly undulate, convex outer lateral margin, followed by two wide, flat anterolateral spines slightly projected; first anterolateral spine bifid, slightly oblique to the middle longitudinal axis; second anterolateral spine trifid, outward directed, forming an angle about 45-degrees to the carapace middle line.

Type species: Tethyranina propinqua (Ristori, 1891) n. comb.

Fossil species: T. propinqua (Ristori, 1891) n. comb.

Etymology: Alluding to the palaeogeographic distribution (Tethys Ocean) and the closer raninid genus, Ranina .

Geological range: early Miocene – early Pleistocene.

Palaeogeographic distribution: The genus appears to be, from the current knowledge of the fossil record, restricted to the paleo-Mediterranean area.

Discussion. We justify the description of the new genus in having a unique combination of substantial distinctive characters within the Ranininae , such as the triangular rostrum, postorbital spine subtriangular flattened, forward directed, with slightly undulate, convex outer lateral margin; first anterolateral spine bifid, and second anterolateral spine trifid, outward directed, forming an angle about 45-degrees to the carapace middle line. The chelipeds are poorly known, as reported by Pasini, Garassino & De Angeli in Baldanza et al. (2014: 274), but appear similar in ornamentation and shape to those of R. ranina .

Tethyranina n. gen differs from the others Ranininae genera as follows:

- Alcespina Pasini & Garassino. 2017 , has trifid point- ed rostrum; first anterolateral spine bifid, forward direct- ed, parallel to the middle longitudinal axis; second wide anterolateral spine pointed, flat, nearly straight anterior margin, strongly outward projected, forming an angle more than 75° (usually about 90°) to carapace middle line, with triangular unequal serrate spines (3-4) on the anterior edge.

- Lophoranina Fabiani, 1910 , has typical carapace surface with typical transverse terraces, usually parallel to one another, two bifid anterolateral spines, 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 carapace.

- Ranina Lamarck, 1801 , has sub-ovate convex carapace with wider surface covered by densely spaced inclined nodes; a single triangular rostrum tip; smaller orbital spines, postorbital spine bifid, forked with inner spine shorter than the inner; two anterolateral palmate trifid spines, first slightly anterolaterally directed, the second diverging at about a 45-degree angle to the carapace longitudinal median axis.

- 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 ex- panded, moderately broad antero-lateral margin, ovoid carapace slightly larger than wide, and carapace ornamentation granular on anterior half and strongly terraced in posterior half widest about half the distance posteriorly on carapace, anterolateral margins appearing to have two projections, 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.

Note. Tethyranina n. gen. seems to include fossil taxa only from the paleo-Mediterranean area. Indeed we cannot exclude that some of the European species (too poorly preserved for a certain assignment) and still considered doubtfully? Ranina (see Pasini & Garassino, 2017a) could also represent different taxa within this genus (see:? Ranina brevispina ,? R. haszlinskyi , and perhaps? R. granulata ).