Antonioranina, Van Bakel & Guinot & Artal & Fraaije & Jagt, 2012

Van Bakel, Barry W. M., Guinot, Danièle, Artal, Pedro, Fraaije, René H. B. & Jagt, John W. M., 2012, A revision of the Palaeocorystoidea and the phylogeny of raninoidian crabs (Crustacea, Decapoda, Brachyura, Podotremata) 3215, Zootaxa 3215 (1), pp. 1-216 : 108

Genus Antonioranina n. gen.

( Figs. 34C, D ; 35A–D )

Type species. Cyrtorhina globosa Beschin, Busulini, De Angeli & Tessier, 1988 , by present designation.

Diagnosis. Carapace oval, with rounded lateral margins. Front triangular, advanced, with 2 adjacent teeth. Orbits small, extraorbital teeth falciform. Orbitofrontal region clearly delimited from dorsal surface of carapace by horizontal row of closely spaced granules. Anterolateral margins with 3 or 4 teeth. Dorsal carapace surface densely granular, posterior portion with larger, scabrous granules. Thoracic sternum narrow; sternite 2 narrow, inclined; sternite 3 V-shaped, wide; sternite 4 elongated, only slightly broadened; episternites 4 subparallel, straight, directed backwards; sternite 5 anteriorly wide, with moderate sternum/exposed pleurites connection; sternite 6 rhomboid, developed, with narrow sternum/exposed pleurites connection; medial line on sternites 5‒8. Buccal frame relatively large, mxp3 narrow; endopod with slender, elongated elements; merus small; exopod wider than endopod. Chelipeds homochelous, homodontous; coxae stout; basis-ischium fused; merus long, robust, curved; carpus elongated; propodus dorsoventrally flattened; fingers long, slender. P2‒P4 rather robust, propodus flattened; P5 reduced, subdorsal.

Species included. Antonioranina fusseli ( Blow & Manning, 1996) , A. globosa ( Beschin, Busulini, De Angeli & Tessier, 1988) , A. ripacurtae ( Artal & Castillo, 2005) and, tentatively, A. oblonga ( Beschin, Busulini, De Angeli & Tessier, 1988) .

Derivation of name. In honour of Antonio De Angeli, in recognition of his numerous contributions to our knowledge of fossil decapod crustaceans from Italy.

Remarks. Carapace features of the new genus are closely similar to those of Cyrtorhina , a name that is here exclusively used for extant members. The two closely allied genera share a broadly ovate carapace, a characteristic orbitofrontal construction and dorsal surface ornament ( Fig. 34 A-D). Differences are nevertheless visible in the ventral construction. In Antonioranina n. gen. sternite 4 is much broader than in the extant genus, where this is markedly restricted between the P1 coxae and practically leaves only room for the gynglymes; episternites 4 are subparallel, nearly straight in fossils, whereas in Cyrtorhina episternite 4 is long and arched. In Antonioranina n. gen. sternite 5 is wider anteriorly; sternite 6 is longer, rhomboid and better developed than in the extant genus. This results in a greater interspace between the bases of P2 and P 3 in the fossil form.

The middle Eocene A. oblonga from northern Italy ( Fig. 35C, D ) is tentatively assigned to the new genus. Carapace features reveal some slight differences: more slender than other species of the genus, elongated, and with the dorsal surface without distinct granules or ornament in the posterior portion. The partial thoracic sternum preserved in this species shows the wide type of sternite 4, hence favouring assignment to the new genus, but also presents a slightly better-developed episternite 4. More completely preserved material is needed to clarify its taxonomic position .

Include here is A. fusseli from the middle Eocene of North Carolina, U.S.A. and A. ripacurtae from the lower Ypresian (lower Eocene) of northeastern Spain, which have similar carapaces; however, ventral parts are still unknown in either species. The latter is the oldest member so far known, and is of much smaller size compared to the type species. More confident taxonomic placement awaits the discovery of material retaining the ventral features.

Figures

FIGURE 34. A, B, Cyrtorhina granulosa Monod, 1956 (Raninidae, Cyrtorhininae), MNHN-B16181 (female), Príncipe, Gulf of Guinea; dorsal and ventral views; C, D, Antonioranina globosa (Beschin, Busulini, De Angeli & Tessier, 1988) n. comb. (Raninidae, Cyrtorhininae), MCZ 1135 (holotype; female) [see also Fig. 35A, B], lower Eocene, Chiampo (Vicenza, northern Italy); dorsal view of carapace and left cheliped, and ventral view showing thoracic sternum and appendages (photographs A, B by J.-F. Dejouannet; C, D by A. De Angeli). Scale bars: 10mm.

FIGURE 35. A, B, Antonioranina globosa (Beschin, Busulini, De Angeli & Tessier, 1988) n. comb. (Raninidae, Cyrtorhininae), MCZ 1135 (holotype; female) [see also Fig. 33C, D], lower Eocene, Chiampo (Vicenza, northern Italy); left lateral view, and posterior view showing abdomen; C, D, Antonioranina oblonga (Beschin, Busulini, De Angeli & Tessier, 1988) n. comb., MCZ 1100 (C, holotype), lower Eocene, Arzignano (Vicenza, northern Italy); MCZ 1102-I.G.211641; D, indeterminate sex; ventral view showing thoracic sternum. (photographs A,B by A. De Angeli) Scale bars: 10mm.