Remyranina ornata ( Remy, 1960 ) Schweitzer & Feldmann, 2010

Schweitzer, Carrie E. & Feldmann, Rodney M., 2010, New fossil decapod crustaceans from the Remy Collection, Muséum national d’Histoire naturelle, Paris, Geodiversitas 32 (3), pp. 399-415 : 401-402

Remyranina ornata ( Remy, 1960) n. comb. ( Fig. 1A )

Raninella ornata Remy, 1960: 57 , fig. 2; figs 8, 9 of the unnumbered plate.

TYPE MATERIAL. — Holotype (dorsal carapace) by monotypy ( MNHN R03847, coll. Tessier).

TYPE LOCALITY. — From probable Eocene rocks on the seacliff below Kraïebouen hill, near Fresco, 5.03°N, 5.31°W, Ivory Coast, Africa ( Remy 1960).

MEASUREMENTS. — Measurements (in mm) taken on the holotype of Remyranina ornata n. comb.: maximum carapace length,> 18.7; maximum carapace width, 14.3; frontal width, 21.0; fronto-orbital width, 10.0.

EMENDED DESCRIPTION

Carapace small for family, longer than wide, moderately vaulted transversely, weakly arched longitudinally; regions not well defined; surface granular in anterior half and strongly terraced posteriorly. Front narrow, about 17% carapace width; fronto-orbital margin moderately broad, about 68% carapace width; maximum carapace width, measured at midlength, less than 80% maximum carapace length; posterior margin broken, estimated to be about 54% maximum width. Front projected slightly in advance of postorbital spines; rostrum sulcate,trifid, with axial spine projected in advance of lateral spines; axis of rostrum with subtle granular ridge. Orbital margin not well preserved; apparently sinuous with at least one orbital fissure at about midpoint; terminating laterally in prominent outer orbital spine. Lateral margin of outer orbital spine convex, widest near tip and narrowing to tip and to intersection with anterolateral margin. Anterolateral margin widening posteriorly; with two spines (broken) dividing margin into thirds; general outline of carapace widest posterior to spines. Posterolateral margins nearly straight, converging posteriorly, rimmed by beaded marginal rim. Posterior margin broken.

Surface of carapace divided into granular anterior half and terraced posterior half. Mesogastric region discernable as extremely subtle pyriform swelling widening posteriorly from rostral ridge to anterior termination of prominent, deep, arcuate branchiocardiac pits. Regions on remainder of front half of carapace indistinguishable; surface with fine gran- ules, somewhat coarser axially and finer laterally. Posterior half of carapace crossed by prominent, continuous to discontinuous, digitate, sinuous terrace structures; terrace structures generally concave forward; tips of digitations broken, fine, about 2.6 digitations per mm, forward-directed. Regions not defined in posterior half.

Remainder of carapace, ventral surface, and appendages not observed.

DISCUSSION

The description of this species given by Remy (1960: 57) is quite complete and little can be added to it. The emended description has been written to use consistent, modern terminology to facilitate comparison with other raninids.

The nature of the fine structure developed on the terraced ornamentation on Remyranina ornata n. comb. is very much like that seen on Lophoranina georgiana (Rathbun, 1935) ( Feldmann et al. 1996: fig. 5), L. precocia Feldmann, Vega, Tucker , García- Barrera & Avendaño, 1996 and L. cristaspina Vega, Cosma, Coutiño, Feldmann, Nyborg, Schweitzer & Waugh, 2001 . In those three species and, in all likelihood, other species within the genus, the digitate margins of terraced structures are broken ends of fine spines that are directed anteriorly ( Vega et al. 2001: fig. 4.7). Th ese small spines were interpreted by Feldmann et al. (1996) to function as hooks to anchor the organism in very fine sediment or to capture bits or organic debris as camouflage ( Savazzi 1981). It is possible that Remyranina ornata n. comb. also possessed small spines that had a similar function.

Subsection HETEROTREMATA Guinot, 1977 Superfamily CALAPPOIDEA De Haan, 1833 Family CALAPPIDAE De Haan, 1833

Figures

FIG. 1. — Fossil Brachyura from Monségur (Gironde, France): A, Remyranina ornata (Remy, 1960) n. comb., cast of holotype, MNHN R03847, dorsal carapace; B, Calappilia? gorodiskii (Remy in Gorodiski & Remy, 1959) n. comb., cast of holotype, MNHN R03840, dorsal carapace; C, D, Calappidae gen. et sp. indet., dorsal (C) and ventral (D) surfaces, MNHN R03836; E, Mursia simplex (Remy, 1960) n. comb., cast of holotype, MNHN R03849, dorsal carapace; F, Szaboa lamarei n. sp., holotype, MNHN R03779, dorsal carapace. Scale bars: 1 cm.