Cretacoranina Mertin, 1941

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 : 19-21

Genus Cretacoranina Mertin, 1941

Cretacoranina Mertin, 1941: 237 .

Type species. Raninella schloenbachi Schlüter, 1879 , by original designation.

Species included. Cretacoranina denisae ( Secretan, 1964) [as Notopocorystes ; Fig.10A, B ], C. fritschi (Glaessner, 1929) [as Notopocorystes ], C. schloenbachi ( Schlüter, 1879) [as Raninella ], C. testacea (Rathbun, 1926) [as Raninella ] and C. trechmanni ( Withers, 1927) [as Ranina ].

Material examined. Cretacoranina denisae : holotype, MNHN F.R03875; paratypes, MNHN F.R03876, F.R03877 and MNHN F.R03878 [as Notopocorystes australis Secretan, 1964 ]; all well-preserved carapaces, lower Campanian, Ampolipoly-Antsirasira-Behamotra, Menabe region, Madagascar (see Charbonnier et al. in press). C. schloenbachi: RME 551.763.333 A 3963 (of which MAB k. 2935 is a plaster cast), two carapaces with associated remains of chelae, upper Campanian, Coesfeld, northwest Germany; MGSB 75290 (of which MAB k. 2936 is a plaster cast), incomplete carapace with associated chela, thoracic sternum and mxp3, Campanian, Puerto de Vitoria, Vitoria, province of Álava, northern Spain. Cretacoranina cf. schloenbachi: NHMM JJ 13448A-C, incomplete carapace, late Maastrichtian ( Belemnitella junior Zone ), Gulpen Formation, Vijlen Member, CPL SA-Haccourt quarry (Liège, Belgium). C. testacea: MAB k. 2934 (a cast of GAB 37-844; Bishop 1983b: table 1), Coon Creek Formation, lower Maastrichtian, Union County, Mississippi, U.S.A. C. trechmanni : holotype, NHM In. 26011, carapace with associated right chela and pereiopod,?Campanian, between Cambridge and Catadupa, Jamaica.

Diagnosis. Carapace medium to large in size, subhexagonal in outline, widest at posteriormost lateral spine, slightly anterior to mid-length; axial carina absent; orbitofrontal margin wide, fissures deep, relatively open, orbital margin spinose; orbits large; front narrow, bifid, lateral sides concave, with axial furrows, 2 diverging distal spines, 2 weak subdistal nodes; anterolateral margins short, weakly arched, with 3 long, sharp, conical spines with narrow triangular bases; posterolateral margins longer, convex ( Cretacoranina schloenbachi [ Fig. 3B–E ], C. trechmanni ) or weakly concave ( C. testacea ; Fig. 3A ), anteriorly with small spine; posterior margin weakly concave, much shorter than orbitofrontal margin; dorsal regions not defined, cervical groove absent, only discrete, short branchiocardiac grooves. Carapace surface covered by dense mosaic of fungiform nodes.

Pterygostome with blunt crests, deep grooves; buccal margin with broad buccal collar. Mxp3 elongated; coxae large, flabelliform; exopod slender, smooth; endopod basis-ischium long, with distinct longitudinal groove.

Thoracic sternum elongated, relatively wide anteriorly; sternite 3 crown shaped; sternite 4 wider than long, trapezoidal, anteriorly much wider than sternite 3; episternite 4 widened; sternites 5, 6 increasingly narrowed, with acute lateral depressions. P1 large, homochelous; upper, lower margins spinose, fingers with strong teeth.

Remarks. Cretacoranina was until recently used to embrace several fossil species, with Tucker (1998: table 4) and De Grave et al. (2009: 29) each recognising 12 species. The current generic definition is too wide, and it is proposed here to subdivide Cretacoranina sensu lato into Cretacoranina emend., Joeranina n. gen., and Ferroranina n. gen., on the basis of dorsal carapace and sternal features ( Table 4). Cretacoranina emend. is distinguished from all other palaeocorystid genera by its large size, complete absence of areolation or cervical groove on the dorsal carapace surface, weak branchiocardiac grooves, long lateral and orbital spines, short furrows confined to a narrow rostrum, and a distinctly wide sternite 4. Because of the derived carapace and sternal characters, Cretacoranina is here considered to be the most derived amongst palaeocorystids.

In addition to the differences mentioned above, Cretacoranina emend. is easily distinguished from Joeranina n. gen. in having a relatively wider carapace, lacking the long and deep frontal furrows, the absence of an axial carina and cuticle exhibiting a microstructure of fungiform nodes (pits and granules in Joeranina n. gen.). Cretacoranina emend. is considered closely related to Ferroranina n. gen., both genera sharing the spinose orbital margin, cuticle microstructure and a wide sternite 4. However, Ferroranina n. gen. differs in having longer frontal furrows, which extend onto the carapace, a medially defined cervical groove and, most obviously, a clearly discernible post-frontal terrace. The front of Cretacoranina emend. also lacks distinct subdistal spines ( Fig. 3B and D ), which are present in Ferroranina n. gen. and Joeranina n. gen.

Members of Cretacoranina emend. are known from the Coniacian to the Maastrichtian, with records from Bohemia ( Czech Republic), England, Germany, northeastern Belgium, Spain, Madagascar, Jamaica and U.S.A.

Figures

FIGURE 3. A, Cretacoranina testacea (Rathbun, 1926b) (Palaeocorystidae), MAB k. 2934 (cast of GAB 37-844; indeterminate sex), lower Maastrichtian, Mississippi (U.S.A), dorsal view of carapace; B, Cretacoranina schloenbachi (Schlüter, 1879), MAB k. 2935 (cast of RME 551.763.333 A 3963; indeterminate sex), upper Campanian, Coesfeld (northwestern Germany), dorsal view of carapace; C–E, Cretacoranina schloenbachi (Schlüter, 1879), MGSB75290 (indeterminate sex), Campanian, Vitoria (northern Spain), dorsal; ventral, and oblique frontal views of carapace. Ventral view shows thoracic sternum and appendages, while left cheliped is visible in E. 3, 4, 5, thoracic sternites 3, 4, 5; P1, P2, pereiopods 1, 2. Scale bars: 5mm.

FIGURE 10. Palaeocorystids from Madagascar; A, B, Cretacoranina denisae (Secretan, 1964), lower Campanian, Ampolipoly-Antsirasira region; (A; paratype, labelled Notopocorystes australis Secretan, 1964; MNHN R03878) and MNHN R03875 (B; holotype); C, F, Notopocorystes bituberculatus Secretan, 1964, MNHN R03951 (holotype), Albian, Malandriandro, dorsal view of carapace, and ventral view showing thoracic sternum; D, E, Joeranina sp., MNHN R03930 (indeterminate sex), Cenomanian, Antsirane, dorsal view of fragmentary carapace and ventral view; G, H, Ferroranina australis (Secretan, 1964) n. comb., MNHN R03874 (G; holotype), lower Campanian, Berere, dorsal view of carapace, and MNHN R03903 (H; paratype), lower Campanian, Ampolipoly-Antsirasira, dorsal view of carapace. Scale bars: 5mm.