Cenomanocarcinus cantabricus, Van Bakel & Guinot & Artal & Fraaije & Jagt, 2012

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 : 54-55

Cenomanocarcinus cantabricus n. sp.

( Fig. 17E, F )

Diagnosis. Carapace of medium size for genus, dorsal surface weakly convex in both directions; anterolateral margins arched, with 4 teeth of similar size, additional larger tooth corresponding to epibranchial region; posterolateral margins with 2 teeth, anteriormost close to epibranchial tooth; dorsal grooves weakly marked; dorsal regions with few, coarse, blunt tubercles; hepatic region without clear tubercles.

Derivation of name. In reference to Cantabria, the region in northern Spain from where specimens of the new species were collected.

Material examined. Holotype, a complete carapace with the majority of cuticle preserved ( MGSB75431 ) (ex Manuel Díaz Collection); paratype ( MGSB75423 ) (ex Pedro Artal Collection), a carapace with fragments of cuticle preserved, both from the Cabo de Ajo sea cliff, within the township of Bareyo (Cantabria) from levels considered to be of Albian age ( Baron-Szabo & Fernández-Mendiola 1997).

Description. Carapace medium sized for genus, subcircular in outline, wider than long; maximum width at epibranchial spine; front advanced, trilobate, with 2 additional blunt teeth at inner orbital corner; orbits small, directed forwards, with 2 short fissures in supraorbital margin, outer orbital node robust, fairly salient; anterolateral margin long, arched, with 5 teeth (excluding outer orbital node, including epibranchial spine), anterior 4 stout, fairly salient, of similar size; epibranchial tooth not completely preserved, appears to have been strong; posterolateral margin longer, converging backwards, sharp edged, with 2 small teeth, anterior one close to epibranchial node, second near posterior corner; posterior margin axially concave, defined by fine rim behind a narrow groove, slightly wider than orbitofrontal margin; dorsal carapace regions weakly vaulted, defined by shallow grooves, with coarse, blunt tubercles; protogastric region with 2 small tubercles; hepatic region barely defined with indistinct inflations, no evident tubercles present; mesogastric region with 2 elongated tubercles; epibranchial region with faint ridge, with large medial tubercle, additional barely inflated lateral tubercle; postbranchial regions with 2 longitudinally positioned tubercles, anterior one larger, rounded, weakly raised, posterior one close to end of lateral margin; cardiac region relatively broad, defined by elongated tubercle, bounded by shallow lateral grooves; intestinal region small, somewhat depressed, bounded by 2 small tubercles; cervical groove weakly marked, even axially, but clearly notching anterolateral margin; branchiocardiac groove well defined at inner portion of epibranchial region. Ventral parts or appendages not preserved. Dorsal carapace surface with dense, small granules.

Remarks. The new species is assigned to Cenomanocarcinus on the basis of the curvature and armature of the anterolateral margin, the strong epibranchial spine, the narrow orbitofrontal margin, triangular five-spined rostrum, division of coarse tubercles on the dorsal carapace, and possession of three ridges on the posterior carapace. The new species can be clearly distinguished from congeners on account of the shallow, weakly defined dorsal grooves; the longitudinal and transverse ridges being only weakly salient; the dorsal surface with few dorsal tubercles; the lack of tubercles in the hepatic region; the posterior half of the carapace with large, blunt tubercles; and the anterior tooth of the posterolateral margin being positioned close to the epibranchial spine.

The only other European species, C. inflatus , shows more marked transverse and longitudinal ridges with more numerous, evenly spaced tubercles and more convex branchial ridges. There is also a strong posterolateral tooth at mid-length, instead of being closer to the epibranchial tooth; there is an additional anterolateral tooth and the hepatic region bears several clear tubercles.

Of the American species, C. beardi exhibits a more subhexagonal carapace, with more divergent posterolateral margins, more salient longitudinal and transverse ridges, stronger dorsal tubercles, a longer epibranchial and posterior anterolateral spine and more distinct H-shaped grooves in the cardiac region. Cenomanocarcinus vanstraeleni exhibits a more subhexagonal carapace; more salient transverse and longitudinal ridges, with more numerous tubercles; the antero- and posterolateral margins with numerous small denticles. Cenomanocarcinus oklahomensis is characterised by stronger longitudinal and transverse ridges, the H-shaped groove pattern in the cardiac region being strongly marked; C. pierrensis exhibits a more distinct, continuous cervical groove; the dorsal tubercles are more raised and conical; the branchial ridges are more salient; the tubercles in the posterior branchial region are not lined up. Cenomanocarcinus pierrensis exhibits a mixed set of characters, which make it difficult to ascribe this species with certainty to Cenomanocarcinus or Necrocarcinus . More completely preserved material is needed to decide in this matter; for the time being, it is retained in the former genus.

Two species from Nigeria were recently described by Collins (2010). Cenomanocarcinus tenuicarinatus , of early Turonian age, has a more elongated carapace; posterolateral margins lack strong teeth and clearly tuberculate hepatic ridges; the axial carina is more salient and continuous, less tuberculate, whereas C. dissimilis , from the lower Cenomanian, exhibits a wider carapace with more distinct longitudinal ridges, clear hepatic tubercles and a narrower cardiac region.

Figures

FIGURE 17. A–D, Cenomanocarcinus beardi Schweitzer, Feldmann, Fam, Hessin, Hetrick, Nyborg & Ross, 2003a (Cenomanocarcinidae); A, D, MAB k. 2544 (female), Cenomanian (Woodbine Formation), Wagner Park, Texas (U.S.A), dorsal view of carapace, and ventral view showing thoracic sternum and mxp3; B, C, MAB k. 2916 and k. 2917 (both indeterminate sex), partial carapaces, same locality and provenance; E, F, Cenomanocarcinus cantabricus n. sp., Albian, Cabo de Ajo (Cantabria, Spain); E, MGSB75431 (holotype; ex Manuel Díaz Collection), dorsal view of carapace; F, MGSB75423 (paratype; ex Pedro Artal Collection), dorsal view of carapace. Scale bars: A-D: 5mm; E, F: 10mm.