Camarocarcinus, Holland & Cvancara, 1958

Guinot, Danièle, Vega, Francisco J. & Van Bakel, Barry W. M., 2008, Cenomanocarcinidae n. fam., a new Cretaceous podotreme family (Crustacea, Decapoda, Brachyura, Raninoidia), with comments on related families, Geodiversitas 30 (4), pp. 681-719 : 681-719

Genus Camarocarcinus Holland & Cvancara, 1958

Remarks

This genus comprises three Paleocene species: C.arnesoni Holland & Cvancara, 1958 ( Holland & Cvancara 1958: 499, figs 2, 3, pl. 74, figs 1-14), the type species, from Paleocene of North Dakota; C. obtusus Jakobsen &Collins, 1979 ( Jakobsen &Collins 1979: 63, pl. 1, figs 3-5), from upper Paleocene of eastern Denmark, and C. quinquetuberculatus Collins & Wienberg Rasmussen, 1992 ( Collins & Wienberg Rasmussen 1992: 33, fig. 19), from middle Paleocene of West Greenland. The genus, first described as a raninid ( Holland & Cvancara 1958: 499, 502), was placed within the Calappidae ( Glaessner 1969: R494; Collins & Wienberg Rasmussen 1992: 33; Schweitzer & Feldmann 2000: 241, 246 key, fig. 3; see also Schweitzer 2001: 810), and then tentatively assigned to the Leucosiidae by Schweitzer et al. (2003a: 34). Affinities between Camarocarcinus and Necrocarcinus have been pointed out ( Glaessner 1960: 46), in particular with “ N. ” pierrensis ( Bishop& Williams 1991:458; Collins&Wienberg Rasmussen1992:38; Fraaye 1994: fig. 1; Fraaije 2002: 914). Fortunately, the venter is preserved in C. arnesoni ( Holland & Cvancara 1958: pl. 74, figs 5, 13) and in C. quinquetuberculatus ( Collins & Wienberg Rasmussen 1992: fig. 19B) and shows extremely deep orbits; a large branchiostegite, bearing an oblique ridge which is markedly raised from the base of buccal frame to at least level of the P3, i.e. the “pterygostomian rim” of Holland & Cvancara (1958: 501, pl. 74, figs 5, 9, 11); elongate “oxystomian” mxp3; and a nearly complete thoracic sternum, last sternite excepted (see

Guinot & Breton 2007: 617).

Cenomanocarcinidae n. fam. ( Crustacea, Decapoda ) from Cretaceous

sternites 2-4. Scale bars: A-E, 10 mm; F, 5 mm.

Guinot D. et al.

Thanks to a cast of the holotype of the thickshelled C. quinquetuberculatus (MGUH 21609; courtesy of S. L. Jakobsen), probably a male ( Fig.9B, D ), the good original description by Collins & Wienberg Rasmussen (1992: 35, 36, fig. 19b) may be completed herein. The sternal plate has a narrow, flat and deeply recessed bottom showing as an undivided plate, lacking a median line (“median furrow” of Collins & Wienberg Rasmussen 1992: 36) and with almost vertical flanges. The anterior sternites are slightly shield-shaped. Sternites 4 to 7 have about the same width along the whole sternal plate; the gynglymes for the articulation of P2 and P3 are visible at the top of the raised lateral flanges of their corresponding sternites (5 and 6), indicating that P2 and P3 (and probably also P4) were close to each other above the median depression; in ventral view, the articular condyles of P2 and P3 coxae on the sternal plate are located well above the level of the median depression. Sternite 4 is markedly overhung by the preserved coxae of the chelipeds (displaced to one side) which effectively are close to each other. The sternal sutures are distinct only on the sides. Such a thoracic sternum ( Fig. 9D ) differs markedly from the wide and largely exposed thoracic sternum in leucosiids (see Guinot & Bouchard 1998: fig. 19).

The thoracic sternum of the Paleocene Camarocarcinus does not correspond to any known configuration in Recent Brachyura and obviously represents the structure of an extinct family. Since we have no data on the venter of Necrocarcinus labeschii , the question is whether the Camarocarcinus sternum represents the necrocarcinid disposition or not. The partially preserved sternum of “ N.” wrighti , with a similar undivided, deep median depression bordered by lateral portions of sternites 4 and 5 (see Feldmann et al. 1993: fig. 29.5), is not substantially different. However, the sternum of Camarocarcinus ( Fig. 9D ) and presumably of “ N.” wrighti is different from that found in Cenomanocarcinus ( Figs 3D, E ; 6A ). The only known thoracic sternum which may be comparable to that of Camarocarcinus is found in the Palaeocorystidae (see Discussion).Thus, the tentative assignment of Camarocarcinus to the Raninoidea , close to the Palaeocorystidae , by Holland & Cvancara

(1958: 502, 503), proves to be correct.

REMARKS ON OTHER GENERA ASSIGNED TO THE NECROCARCINIDAE

Figures

FIG. 9.— A, “Necrocarcinus” senonensis Schlüter in von der Marck & Schlüter 1868,middle Danian,Denmark,Fakse quarry,reconstructed photograph of the carapace (Collins & Jakobsen 1995: pl. 10, fig. 11), with two strong lateral spines; B, D, Camarocarcinus quinquetuberculatus Collins & Wienberg Rasmussen,1992, holotype, probably male (cast, MGUH 21609;courtesy of S. L. Jakobsen), dorsal and ventral views; C, Cretacoranina cf. dichrous (Stenzel, 1945) (Palaeocorystidae), middle Cenomanian, Karai Formation, between Odiyam and Kunnam,Tamil Nadu, India,leg.A.S.Gale, 1999 (OUM KY.2861), thoracic sternum, see individualised sternite 3, lateral expansions of sternite 4,and deep sutures 4/5; E, F, Orithopsis tricarinata (Bell,1863);E, upper Albian,Upper Greensand,England,Cowstones,holotype of O. bonneyi Carter, 1872, “unretouched photograph of specimen prepared since the original illustration” (Wright & Collins 1972: pl. 12, fig.3) (SM B58557);F, upper Albian,Cambridge Greensand (KBIN,Van Straelen Collection,unnumbered),thoracic sternum,with preserved

FIG. 3. — A-D, F, Cenomanocarcinus vanstraeleni Stenzel, 1945; A, B, C, F, late Cenomanian-Turonian, Eagle Ford Group, Turonian, Múzquiz, Coahuila, Mexico; D, late Cenomanian, Eagle Ford Group, Britton Formation, California Crossing, Dallas County, Texas; E, Cenomanocarcinus sp., upper Albian,Colombia;A, female (MUZ-216),thoracic sternum (anterior portion of sternite 4 exposed) covered laterally by abdomen, mxp3, and pereiopods; at left, inflated P4 propodus (MUZ-212); B, mxp3 (MUZ-212); C, female (MUZ-201), sternite 4 with pair of tubercles, and abdomen;D,?female,paralectotype (BEG-21091-A1),thoracic sternum without abdomen; E, thoracic sternum (associated with carapace) showing a crown-shaped plate,long sternite 4, and deep, curved sutures 4/5 (INGEOMINAS/ Jur-1; Vega et al. in study); F, male (MUZ-215), thoracic sternum (see deep sutures 4/5) and abdomen. Scale bars: 10 mm.

FIG. 6. — Cenomanocarcinus aff. vanstraeleni Stenzel, 1945, Coniacian (according to the accompanying label), Apulo, Colombia, female, 160 × 150 mm (estimated carapace measurements not including lateral spines) (RGM M902):A, ventral view; B, chelipeds.