Ibericancridae

Artal, Pedro, Guinot, Danièle, Bakel, Barry Van & Castillo, Juan, 2008, Ibericancridae, a new dakoticancroid family (Decapoda, Brachyura, Podotremata) from the upper Campanian (Upper Cretaceous) of Spain, Zootaxa 1907, pp. 1-27 : 7-8

Ibericancridae n. fam.

Type genus. Ibericancer n. gen. (gender masculine).

Diagnosis. Large-sized crabs; carapace suboval, thick, with high flanks; fronto-orbital margin gently salient; front relatively broad, protuberant at inner-orbital angles, somewhat concave from dorsal view, noticeably notched medially; rostrum narrow, strongly downturned, axially grooved, bilobed; orbits small, directed forwards, with deep fissure and supramarginal tooth; dorsal regions relatively inflated, poorly differentiated except for moderately deep branchiocardiac grooves, some depressions, scarcely pronounced swellings; posterior margin of carapace concave, rimmed, axially raised; pterygostomial region large; pleural suture at sides of carapace; thoracic sternum well developed, conspicuously elevated laterally, with strong pointed prominence on each side of the anterior portion of sternite 4; only relative narrow portion of sternum exposed laterally at level of P2–P4; sternum bent, narrowing posteriorly at level of P4, P5; sternite 5 relatively large, sternite 6 as narrow, elongated plate, sternite 7 very reduced, oblique, sternite 8 completely covered by abdomen, not exposed; abdomen weakly dimorphic sexually, relatively broad in males; locking mechanism of press button type; male gonopore on P5 coxa; female gonopore on P3 coxa; spermathecae at extremities of suture 7/8; chelipeds homochelous, slender, with propodus longer than wide; P2, P3 extremely robust, long; P4, P5 markedly reduced, subequal, subdorsal.

Remarks. There are many differences between Ibericancridae n. fam. and the Dakoticancridae Rathbun, 1917 . These differences mostly concern ventral characters but there are additional differences in the carapaces. In the Dakoticancridae the deflected rostrum is directly connected to the orbital margins, and the orbitofrontal margin is broadly concave, with advanced outer orbital spines. In Ibericancer n. gen. the frontal margin is more salient, somewhat concave in dorsal view, clearly notched medially, and the outer corners are lobed; the rostrum is strongly downturned, with a pronounced axial furrow. In the new genus the orbital margin is small in dorsal view, directed forwards, with the supraorbital tooth bounded by fissures. In contrast, in the Dakoticancridae the orbits are large and broadly concave, divided into two concave portions in dorsal view. Bishop (1984b) and Bishop et al. (1998) provided a detailed description of the orbits and of a presumed sensory structure, ‘orbital bulla reticularis’ found in D. overana .

In Ibericancer n. gen. the posterior margin is concave, slightly convex in dorsal view through the raised posterior portion of the carapace, extremely thick, and medially inflated by the robust conical protuberance of the intestinal region; when seen from posterior view, it shows an unusual V-shape with the apex directed upwards. The posterior margin of the Dakoticancridae is nearly straight in dorsal view, thin, slightly rimmed, and there is no space in the dorso-ventral connection.

The thoracic sternum of Ibericancer n. gen. is narrower than in the Dakoticancridae , elevated at the sides, stout, and with very thick cuticle; sternites 1–4 are smooth and continuous axially, while in Dakoticancridae the sternum is broader, the upper margin of sternite 3 is noticeably rimmed, marking a discontinuity of the anterior sternites 1, 2 (see Fig. 3D ). The abdomen shows a weak sexual dimorphism, in contrast to the Dakoticancridae . The supposed propodus of Tetracarcinus figured by Bishop et al. (1998: fig. 2.2) was noted as not having been found attached to the crab. This isolated propodus could be perfectly well assigned to a macruran, probably close to Ctenocheles Kishinouye, 1926 .

The cheliped propodus in the Ibericancridae n. fam. is slender and somewhat dorsoventrally flattened, longer than wide, with very thin and long fingers. In dakoticancrids, the chelipeds are variable among the different species, varying from robust and globose in D. australis and Avitelmessus to slender in D. overana .

Both P4 and P5 are subdorsally located, strongly reduced in thickness but weakly reduced in length, subequal, whereas in the presently known Dakoticancridae only the P5, when preserved, is reduced and subdorsal.

The dorsal regions, somewhat less pronounced in the anterior portion of the carapace, are more uniformly inflated than in the four genera assigned to the family Dakoticancridae . Ibericancer n. gen. shows small and dense granules uniformly distributed on the carapace, thoracic sternum and pereiopods, in contrast to larger granules that tend to be grouped on the more prominent regions in D. overana , Tetracarcinus , Seorsus and Avitelmessus . In the latter, there are spines on the carapace, lateral carapace margins and pereiopods (see Kesling & Reimann 1957). The granulation over the entire surface is more distinct in D. australis than in Ibericancer sanchoi n. gen., n. sp.

Ibericancer sanchoi n. gen., n. sp. is closer to Dakoticancer autralis than to D. overana by having a narrow and more quadrate carapace (more parallel sides in D. australis ), prominent posterior portion (see key in Bishop et al. 1998: 246), narrower thoracic sternum, and more uniformly distributed dorsal granulation; the propodus is long and slender as in D. overana .

Figures

FIGURE 3 A – E. Casts of Dakoticancer overana; A. MNHN B 22902 - 1 (cast of USNM 173529 - 1), ventral view of a male; B. posterior view of the same specimen; C. details of the abdominal holding mechanism, the arrow indicating the press button protuberance on sternite 5; D. MNHM B 22902 - 2 (cast of USNM 173529 - 2), ventral view of a female, without the abdomen; the arrow indicating the aperture of the spermatheca; E. MNHN B 22903 (cast of USNM 173544), ventral view of a female; the arrow indicating the female gonopore on P 3 coxa.