Ranina palmea E. Sismonda, 1846: 64

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 : 5-7

Ranina palmea E. Sismonda, 1846: 64 , Pl. 3, figs. 3, 4.

Ranina palmea – Reuss 1859: 21. – Crema 1895: 672, Pl. 3, figs. 12a-e. – A. Milne Edwards 1872: 4, 9. – Fabiani 1910: 9. – Glaessner 1929: 362. – De Angeli et al. 2009: 120, 121. – De Angeli & Beschin 2011: 13, 15. – Van Bakel et al. 2012: 209. – Karasawa et al. 2014: 260.

Hela palmea - Lőrenthey in Lőrenthey & Beurlen 1929: 109.

Diagnosis: Sismonda (1846) only provided a limited morphological description and comparisons (in Italian language).

Type material: Reale Museo Geologico di Torino, today lost (Ormezzano pers. comm., 2014).

Type locality: Torino Hill sandstone (Piedmont, northwestern Italy) .

Geological age: Neogene (middle Miocene, “Helvetian”– now Serravallian).

Examined material: Line drawings proposed by Sismonda (1846: Pl. 3, figs. 3, 4) and later by Crema (1895: Pl. 3, figs. 12a-e).

Description: We provide herein a literal translation of the original description by the author, wrote in old Italian language and never previously translated, to facilitate comparisons and discussion of this lost species.

Literal translation: “… The specimen consists of a big sized crustacean, having maximum transversal diameter of 0,077 (meters), longitudinal of 0,083 (meters), abdomen excluded. (The carapace) has a triangular shield leaning to an ovate shape, convex dorsally and with thousands of small tubercles or spines fairly elongated, flattened, forward directed, bigger toward the abdomen, worsen to thinner tubercles on the frontal region. Upper, or frontal margin concave, divided in nine lobes, of which the outermost are separated each other by deep furrows. The central lobe is scarcely projected, origi- nating a triangular rostrum, strengthen at each side by a fairly acute tooth; this tooth is shorter than the others (teeth), giving the front concave, a distinctive character of the male individuals, as observed by Milne-Edwards (instead) the female front is arcuate and convex; and any- more, in added to the sexual differences, according to De Haan, that the upper margin of the palms of the Ranina males are armed by obtuse spines, while the spines are acute in females. The lobes nearby the median (mytoy- ens internes) end in a single tooth; the following (lobes) (mitoyens externes) are wide, flattened, and ending with two teeth, each splitting in other ones smaller, a detail not well represented in the drawing (= Pl. 3, fig. 3); finally the more external frontal lobes, the last and second last, are the more developed, flattened, wide, ending in three points or triangular teeth, they also bears smaller pointed spines here and there along the margins of the main tips of the anterolateral spines, and this is the main difference among the described specimen and the Ranina Dentata by Latreille [= R. ranina (Linnaeus, 1758) ]. Lateral margins convex, shaw-like rimmed, abdomen narrow, triangular, elongate, slightly down-turned, with seven dorsally carinate rings, having convex anterior margin, concave posteriorly. The sternum and maxilliped are covered by an hardened sandstone.... Walking legs poorly preserved. The left distal thoracic cheliped (fig. 4) is the only more or less preserved, limited to the carpus and manus that is very flattened, both are covered by rather higth and pro- truded small tubercles; the upper margins bears two large spines, moreover the lower margin of the fixed finger has five teeth, the dactylus, flattened, curved also bears some teeth along the margins. Fossil in the Miocene sandstone from the Torino hill.”.

Discussion. Since the type material is lost, the discussion is simply based on the original description by Sismonda (1846) and observations on the line drawings proposed by Sismonda (1846: Pl. 3, figs. 3, 4) and later by Crema (1895: Pl. 3, figs. 12a-e).

Crema (1895: 672) added some observations to the description by Sismonda (1846), and proposed a re-drawing of the species under direct observation: “(I) Refigure the right chela (fig. 12c) and propose a schematic representation of the anterior lateral side (fig. 12a) of the specimen, due that the original figures reported to date contains several inaccuracy” (literal translation). Moreover the author reported “(I) examined also several carapace fragments and the dorsal shield of a young specimen…”. The fossil site of the additional material is not clearly specified in the description by Crema, but the author reported at the end of his notes “ Elveziano: Colli Torinesi, Sciolze. Bardassano [Elvezian (Serravalian); Torino Hills, Sciolze. Bardassano – Piemont. northwestern Italy]”, that is not the type locality of the Sismonda’s specimen. Crema (1895: 672, 673) pointed out that the dorsal ornamentation “… specially in the anterior and median parts shows other smaller tubercles among the spiny tubercles, less marked than in the living species (= R. ranina ) …”; that “ the abdomen is very different from the ideal reconstruction proposed by Sismonda, shows the first five segments well preserved, but lacks of the telson; is perfectly close to this of R. serrata (= R. ranina )” (Pl. 3, fig. 12b); and moreover that “… the left chela is about 1/3 bigger than the right …(Pl. 3, fig. 12c), and that “ The parts observables of the walking legs are close to the of the R. serrata ”(Pl. 3, fig. 12e).

Ranina palmea shows all the typical proxy characters of the genus, such as: carapace subovate, convex dorsally, ornate by forward pointed spines or tubercles forward directed, smaller on the frontal region; rostrum triangular with two nearly acute spines at the wide bottom; anterolateral spines flattened and wide, trifid, the first one wider; the second one more inclined at a less than a 45-degree angle to the carapace longitudinal median axis, and in having same shape and ornamentation on the flattened spiny chela and elongate carpus; serrate anterolateral margin, convex; long serrate posterolateral margin, narrowing posteriorly, posterior margin straight; elongate, triangular pleon, smooth, with somites dorsally inflated longitudinally, convex anteriorly and nearly concave posteriorly; flattened, tuberculate chela with two wide dorsal spines forward directed; curved dactylus, flattened, with dentate dorsal margin; flattened fixed finger, occlusal margin with five rounded teeth.

Moreover, based upon the body size (lcxp: 83 mm; wcxp: 77 mm) and presence of well-developed anterolateral spines, according to Sismonda (1846), the specimens might belong to an adult (mature) male, in the hypothesis that also the fossil mature representatives of Ranina had a notable sexual difference in the shape of the anterolateral spines, as in the extant type species.

An hypothesis for the female and male growth-reproductive patterns (= adult stages) of the extant R. ranina is given for instance by the model proposed by Minagawa (1993: 2029, fig. 8), and also inferable to the different stages of growth of carapaces figured by Sakai (1937: 179, text-fig. 45), whereas according to Nyborg (pers. comm., 2016), the juvenile stage drawing proposed by Sakai (1937) is incorrect at level of the anterolateral spine (figured as bifid and trifid), whereas both are always trifid.

According to Sismonda (1846: 65) and Crema (1895: 672), the specimen has a general carapace shape and dorsal ornamentation close to those of the adult males of extant R. ranina . Indeed, Sismonda (1846: 65), pointed out that the “ major difference among the fossil described (= Ranina palmea ) and the R. dentata by Latreille [= R. ranina (Linnaeus, 1758) ]”, consist in the presence on “… the more external lobes of the front, the last and second one are the more developed, flattened, wide, ending in three points or triangular teeth, then also bearing smaller pointed spines here and there along the margins of the main tips of the anterolateral spines … ”.

The relative shortness of the frontal spines, the shorter wider triangular rostrum, the more serrate, spiny postorbital bifid spine, and the presence of accessorial sparse spines along both anterolateral spines are characters that can justify the specific assignment to R. palmea .

In conclusion we can consider R. palmea as a valid species within Ranina , representing the oldest fossil species known for the genus. The presence of Ranina in the paleo-Mediterranean almost since the middle Miocene is very intriguing, opening a new look to the possible origins for the genus, joined to some paleo-geographic problematics.