Graptocarcinus urbasaensis, Van, Barry W. M., Guinot, Danièle, Corral, José Carmelo & Artal, Pedro, 2012

Van, Barry W. M., Guinot, Danièle, Corral, José Carmelo & Artal, Pedro, 2012, Graptocarcininae n. subfam., an extinct subfamily of Dynomenidae Ortmann, 1892 (Crustacea, Brachyura, Podotremata), Zootaxa 3534, pp. 40-52 : 47-50

Graptocarcinus urbasaensis n. sp.

( Figs. 2 , 3 )

Etymology. From Urbasa, the Spanish name of the mountain range where the fossils were collected.

Material examined. Holotype: MGSB 78.337a–c (female), carapace with abdomen, left-hand cheliped, and pereiopods, Santonian, Contrasta, Álava province, Spain. Paratypes: MCNA 8562 (male), well preserved carapace with abdomen, left-hand cheliped, and pereiopods, Santonian, Egibil quarry (“Cantera de Margas”), Olazti- Olazagutía, Navarra Province, Spain. MGSB 28.148a–b, carapace and isolated cheliped, Maastrichtian, Puerto de Urbasa, Navarra Province, Spain.

Description. Carapace relatively large (maximum carapace width 34mm), wider than long, width 1.25x length, widest slightly posterior to midlength. Dorsal surface convex in longitudinal section, gently tumid in transverse section, with strongly inclined sides; surface ornamented with large, blunt granules, cuticle with numerous minute setal pits. Cervical groove indistinct, only defined in medial third, broadly V-shaped. Branchial groove obsolete, branchiocardiac grooves curved, crescent-shaped, diverging anteriorly. Anterolateral margins long, evenly curved, well defined, sharp, without teeth, set with granules; corner of lateral margins produced as sharp flange; posterolateral margin weakly defined, blunt, straight in dorsal view; posterior margin relatively narrow, straight in dorsal view, markedly concave per se, distinctly thickened. Front weakly projecting, strongly downturned, broadly triangular, continuous with supraorbital margin; supraorbital margin oblique, arched, continuous above orbits, thickened, rimmed, without notches; infraorbital margin short, without notches. Orbits oblique, elongated, well defined, outer orbital corner rounded. Subhepatic region, pterygostome flattened, grooved, surface non-ornamented; cervical groove ventrally present as shallow groove. Pleural line absent; branchiostegite low, inclined.

Mxp3 operculiform, coxae elongated, twisted; endopod: basis separated from ischium by complete, distinct suture, ischium smooth, widened distally, inner margin arched; exopod: incompletely preserved, rather wide, straight. Abdomen entirely covering thoracic sternum (i.e. in width, length) in both sexes, thus in contact with pereiopod and mxp3 coxae; sexual dimorphism distinct, female abdomen much wider than in male (31% of maximum carapace width, versus 23% in male); all somites separate, somites 2–6 subequal in length, width; somites with median portion vaulted, lateral portions produced as anteriorly directed flanges. First somite subdorsal, conspicuously short, strongly curved, matching curvature of concave posterior carapace margin; somite 6 with salient dorsal uropods along majority of somite length. Telson elongate, posterior corners rounded, posterior part with subvertical margins with weak depressions, anteriorly broadly triangular with straight sides, rounded tip. Coxal abdominal holding mechanism present in both sexes at P1–P4 coxae; P1 coxa with granules, P2–P4 coxae with distinct granular prominence, overhanging lateral portions of abdominal somites. P1 strongly developed; basis, ischium separated; merus thick, rounded triangular in section, lower margin arched; carpus short, granular; chelipeds robust; propodus, carpus proximally with distinctive articulating bulge; palm tumid, coarsely granular, with rounded upper, lower margins; fingers short, stout, dactylus with furrow parallel to arched upper margin, both fingers with single crushing tooth, distally spoon-tipped. P2–P4 (partially preserved) robust; coxae large, anteriorly with distinctive coxo-sternal sliding arch; merus long, oval in section; carpus short; elements of P1–P4 granular. P5 (partially preserved) conspicuously reduced, carried subdorsally in oblique position, smooth.

Graptocarcinus urbasaensis n. sp. differs from G. m u i r i by the absence of an anterior mesogastric process and frontal sulcus (present in G. m u i r i); the supraorbital margin being more vaulted than G. m u i r i; and having the corner of the lateral carapace margins produced as a sharp flange (blunt in G. m u i r i).

G. urbasaensis n. sp. differs from G. texanus by the absence of an anterior mesogastric process and frontal sulcus (present in G. texanus ); the supraorbital margin being more vaulted than in G. texanus ; having the corner of the lateral carapace margins produced as a sharp flange (blunt in G. texanus ); the carapace being wider relative to its length; having sparser granules on the dorsal carapace surface (more granular in G. texanus ); the anterolateral carapace margin not being strongly granular as in G. texanus ; and the posterolateral carapace margin being blunt (sharp in G. texanus ).

G. urbasaensis n. sp. differs from G. bellonii by absence of the anterior mesogastric process / frontal sulcus (present in G. bellonii ); having much larger orbits relative to the carapace than G. bellonii ; and the corner of lateral carapace margins produced as a sharp flange (blunt in G. b e l l o n i i).

The claw figured by Jagt et al. (2010: fig.4e–h) as Graptocarcinus sp. differs from the claws of G. urbasaensis n. sp. and G. texanus , the fingers being more spatulate and without teeth.

Amézarri Grandal et al. (1977: 49, 50) illustrated the dorsal and ventral side of a well preserved female specimen with pereiopods, abdomen and mxp3 that corresponds to the new species described here, but they failed to formally describe and name it. This publication is rare, never referred to, and the whereabouts of the specimen is unknown.

Figures

FIGURE 2. Graptocarcinus urbasaensis n. sp., MGSB 78.337 a – c (holotype, female), Santonian, Contrasta, Álava, Spain. A, dorsal view; B, right lateral view; C, ventral view; D, frontal view; E, posterior view; F, left cheliped. a 1, a 2, a 3, a 4, a 5, a 6, abdominal somites 1, 2, 3, 4, 5, 6; d, depression; u, uropod; t, telson. Scale bars: 10 mm. Specimen whitened with ammonium chloride sublimate prior to photography.

FIGURE 3. Graptocarcinus urbasaensis n. sp., MCNA 8562 (paratype, male), Santonian, Egibil quarry, Olazti-Olazagutía, Navarra, Spain. A, dorsal view; B, frontal view; C, ventral view; D, posterior view; E, detail of abdomen and pereiopod coxae; F, detail of posterior view. a 1, a 2, a 3, a 4, a 5, a 6, abdominal somites 1, 2, 3, 4, 5, 6; ab, articulating bulge; cx 1, cx 2, cx 3, cx 4, cx 5, P 1 – P 5 coxae; cmxp 3, mxp 3 coxa; d, depression; gr, granules; mP 5, P 5 merus; pr, prominence; pt, pterygostome; u, uropod; t, telson. Scale bars: 10 mm. Specimen whitened with ammonium chloride sublimate prior to photography.