Ranina, Lamarck, 1801

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 : 4-5

Ranina - De Haan 1839: 137. – Poore 2004: 322. – Karasawa et al. 2014: 45.

Diagnosis by Karasawa et al. (2014): Carapace generally widest in anterior one quarter, narrowing posteriorly; rostrum trifid, with axial two spines serving as inner orbital spines, central spine triangular; intra- and outer orbital spines triangular; anterolateral margin generally with two spines that are bifid or trifid, often larger and more complexly ornamented in males; postfrontal region depressed slightly below level of remainder of carapace, can be granular or scabrous; remainder of carapace ornamented with forward directed spines; appendages and pterygstome ornamented with less densely-spaced spines; sternum smooth.

Remarks: The diagnosis of Ranina is based on the characters of the extant type species R. ranina .

The systematics adopted in this study follows partially the recent diagnosis for the genus proposed by Karasawa et al. (2014: 45), but pointing out that the first and second anterolateral spines are trifid in both sexes, also in juvenile stages, and never bifid as previously reported by some authors (Sakai, 1937; Poore, 2004; Karasawa et al. 2014). Moreover, we add herein some others useful proxy generic characters to the diagnosis by Karasawa et. al. (2014), as follows:

- the postorbital spine shape, divided distally into two spines, is forked (= bifid), with the outer spine shorter than the inner; however, as pointed out by Luque (pers. comm., 2017) “ some small specimens seem to have not just bifid but multi-spinose outer orbital/postorbital spines; this clearly seems to change during ontogeny, and those additional small spines become obsolete and disappear ”.

- the first anterolateral spine, slightly inclined outward and the second anterolateral spine more inclined at about a 45-degree angle to the carapace longitudinal median axis, never strongly forward or outward directed; however, as pointed out by Luque (pers. comm., 2017) “ this seems to change quite a bit among populations (of extant R. ranina ); some tend to have closely spaced spines directed forwards, whereas others have a wider spaced spines and inclined at more pronounced angles ”. We were unable, however, to consider in the fossil record these variations due to the scarcity of specimens.

The combination of these unambiguous additional morphological characters are also adopted in this study to distinguish Ranina from others fossil genera within Ranininae .

Type species: Cancer raninus Linnaeus, 1758 , subsequent designation by Latreille (1810).

Stratigraphic range: middle Miocene – middle Pleistocene and extant.

Including fossil species: Ranina palmea E. Sismonda, 1846 ; R. ranina (Linnaeus, 1758) .

Paleogeographic distribution: Mediterranean area (exclusively fossil) - Indo-Racific area (fossil and extant).

Emended diagnosis (present study): Carapace subovoid, wider anteriorly; dorsal ornamentation, with sparse granular-spiny tubercles directed forward, never ranging into tegulate rims; triangular rostrum; postorbital spine bifid, forked, with the outer spine shorter than the inner in adult extant species [small specimens (immaturejuveniles) seem to have not just bifid but multi-spinose outer orbital-postorbital spines, whereas in some large sized specimens the secondary spine can be much developed than the outer-postorbital spine (Luque pers. comm., 2017)]; first and second anterolateral spines always trifid, often larger and more complexly ornamented in males; first one slightly inclined outward with the second diverging usually at but not more than a 45-degree angle to the carapace longitudinal median axis, more complexly ornamented and developed in adult males. Large, flat chelae with transverse dactylus; dactylus bearing 7 spines on the upper margin and pointed tip downward directed; propodus flat, lined with tubercles; propodus with 2 prominent dorsal spines and 5 prominent spines on the lower margin; elongate carpus with 2 parallel spine on the anterior upper margin pointing outward in opposite direction; merus with a single spine on the upper anterior margin. Appendages and pterygstome ornamented with less densely-spaced spines; sternum shield smooth, s1-s3 fused, s4 broad at the anterior margin, convex and lateral margin concave; s5 with shallow longitudinal depression.