Rogueus belgodereae, van Bakel & Ossó & Téodori, 2023

van Bakel, Barry W. M., Ossó, Àlex & Téodori, Dominique, 2023, Rogueus belgodereae, a new raninoid crab (Crustacea: Brachyura: Raninoidea) from the Upper Palaeocene (Thanetian) of Southern France, with comments on early palaeocene decapod crustacean faunules, Palaeontologia Electronica (a 45) 26 (3), pp. 1-16 : 9-10

Rogueus belgodereae n. sp.

Figure 3 A-C zoobank.org/ AF048BFB-6114-444C-BECC-662D65C4B05C

Etymology. Named after Valérie Belgodere (Pechbonnieu, France), who has supported the second author (D.T.) and his passion, for more than 30 years.

Diagnosis. Rogueus with short, stout anterolateral spines, a widened orbitofrontal margin with anterolaterally directed outer orbital spines, and smooth dorsal carapace surface.

Type. The holotype is MNHN.F.A88045, a well-preserved complete carapace with the cuticle preserved; maximum carapace length: 26.5 mm, maximum carapace width (including lateral spines): 19.5 mm, orbitofrontal width: 12.5 mm. Paratypes MNHN.F.A88046 and MNHN.F.A88047 represent partial carapaces with portions of cuticle preserved. All material comes from the Lafarge quarry, Martres Tolosane, Haute Garonne, France .

Description. Carapace of moderate size (length of holotype: 26.5 mm, width 19.5 mm), elongated, width 74% of length, outline subhexagonal, maximum width (excluding anterolateral spine) at approximately 43% of total carapace length from front; dorsal surface gently convex in transverse cross section, gently arched in longitudinal crosssection. Orbitofrontal width approximately 69% of maximum carapace width; front narrow, tip blunt, bifid; orbits large, horizontally orientated in dorsal view, supraorbital margin sinuous, with a single short, distinct notch, inner portion of orbital margin concave, outer part first convex, then concave towards prominent outer orbital spine, directed slightly outwards. Anterolateral margins short, rounded in cross section, short concave margin continuously curved into robust anterolateral spine, with broad basis, directed anteriorly and outwardly, anterior margin with anteriorly directed sub-spine. Margins posterior to the lateral spines diverging, straight or gently convex. Posterolateral margins long, smooth, gently sinuous, convergent. Posterior margin straight, narrow (approximately 28% maximum carapace width).

Dorsal regions undefined; cervical groove visible axially as arched scars; hepatic region weakly swollen, cardiac region large, wide, defined by crescent-shaped branchiocardiac grooves. Gastric pits minute, well separated.

Dorsal carapace surface appears overall smooth, exocuticle not preserved. Diminutive granules and pits present in frontal region and near base of anterolateral spine.

Remarks. Rogueus belgodereae n. sp. differs from the type of the genus, R. orri from the lower middle Eocene of southwestern Oregon, U.S.A., in having clearly shorter, more robust lateral spines (slenderer and more elongated in R. orri ), a stronger, more laterally directed outer orbital spine, and a smoother, less pitted carapace surface microstructure. Rogueus robustus , from the middle Palaeocene of northern Sjaelland, Denmark, is readily distinguished from R. belgodereae n. sp. by the former clearly having elongated anterolateral spines, a longer anterolateral margin between the outer orbital spine and anterolateral spines, and clearly pitted carapace microstructure. The subdistal spine of the anterolateral spine is distally placed in R. orri and R. robustus , giving the elongated anterolateral spine a bifurcate appearance; because the anterolateral spine is so short in R. belgodereae n. sp. the subdistal spine is positioned halfway the anterolateral spine.

Figures

FIGURE 3. A-C Rogueus belgodereae n.sp, A: holotype MNHN.F.A88045. B, paratype MNHN.F.A88046, C, paratype MNHN.F.A88047. Scale bar equals 1 cm.