Cenomanocarcinus vanstraeleni Stenzel, 1945

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

Cenomanocarcinus vanstraeleni Stenzel, 1945 ( Figs 2 ; 3 A-D, F; 4; 5)

MATERIAL EXAMINED. — Late Cenomanian, Eagle Ford Group , Britton Formation , California Crossing , Dallas County, Texas , 9 syntypes ; Stenzel’s syntype 3 ( BEG- 21098 ) is designated here as lectotype, all others become paralectotypes: males ( BEG-21079-2 , BEG-21079-6 , BEG-21079-12 , BEG-21088 , BEG-21090 , BEG-21092 ), females ( BEG-21079-1 , BEG-21091 ). — Middle Turonian, Mancos Shale , 50 km northwest of Albuquerque , 1 specimen, possibly a female (UNM-3938). — Turonian , Eagle Ford Group , Mexico, Múzquiz , Coahuila, 11 specimens, males (MUZ-212, MUZ-215, MUZ-226, IGM-7655 ), females (MUZ-201, MUZ-204, MUZ-208, MUZ-209, MUZ-211, MUZ-216, MUZ-246).— Lower to middle Turonian , Colombia, San Rafael Formation , 1 male (UN-DG-CR004), 2 females (INGEOMINAS- NZ4b-03, INGEOMINAS-B4V/6). — Coniacian (according to label with the specimen), Colombia, Apulo , 1 female, 160 × 150 mm (estimated carapace measurements, exclusive of lateral spines), Cenomanocarcinus aff. vanstraeleni Stenzel, 1945 ( RGM M902 ) .

OCCURRENCE. — Cenomanian-Turonian of New Mexico, Texas, Mexico (Eagle Ford Group) and Colombia.

ECOLOGY AND BIOLOGY. — The Cenomanocarcinidae n. fam. as exemplified by the large-sized C. vanstraeleni exhibit extremely thin carapace cuticle, overall construction being strengthened by elevations (the H-shape), and

lightweight. The carapace which bears strong epibranchial

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

carapace; F, detail of the front. Scale bars: A-E, 10 mm; F, 5 mm.

Guinot D. et al.

spines which would have deterred possible predators. The chelae are armed with strong fingers, and the tips of fingers with hooks to catch or clamp, whereas the molariform teeth of the fingers may have been used to crush objects. The morphology is perfectly suited to catch and crush (swimming) molluscs such as ammonites. The flattened propodi of P3 and P4, to increase surface area, are modified for swimming and burying.

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

Remarks

Cenomanocarcinus vanstraeleni Stenzel, 1945 (Sten-

zel 1945: 447, fig. 15, pl. 44) was established for nine specimens, all syntypes, from Texas. Recent biostratigraphic researches on the Britton For-

mation of the Eagle Ford Group indicate a late

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Cenomanian age for the stratigraphic unit that includes this species ( Kennedy 1988; Friedman 2002; Jacobs et al. 2005). In the type series, syntype 3 with a well-preserved venter, figured by Stenzel (1945: pl. 44, fig. 3), is designated here as lectotype (all other specimens becoming paralectotypes; see Material examined).

It was interpreted by Stenzel (1945) as a female probably because of the width of the abdomen (Fig. 5A, B). This wide abdomen may also be that of a male since even in males the space between the legs (i.e. the sterno-abdominal depression) is entirely filled laterally by a relatively wide abdomen. A portion of the sternum is visible anteriorly, as indicated by Stenzel (1945: pl. 44, fig. 4; see also

Stenzel 1952: 215, pl. 59, figs 9, 10).

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

part of left chela. Scale bars: 10 mm.

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Scale bar: 50 mm.

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

bar: 10 mm.

Guinot D. et al.

The relationships thoracic sternum/abdomen evoke a typical podotreme organization following Guinot & Bouchard (1998) and Guinot & Tavares (2001). Such a condition led Larghi (2004) and Vega et al. (2007) to include C. vanstraeleni in the Podotremata, a view similarly envisaged by Guinot & Quenette (2005: 329) and Guinot & Breton (2006: 616). Cenomanocarcinus vanstraeleni , the commonest crustacean species in the Múzquiz deposits of Mexico, was documented in detail by Vega et al. (2007): it is among the largest crabs known from the Cretaceous (see also Finsley 1989: 98, 99, pl. 78, photographs 307, 308).

Important material of C. vanstraeleni from several localities in Mexico, Colombia, and Texas has been examined and compared for the present study. Virtually all parts (with the exception of eyes, cephalic appendages and pleopods) of C.vanstraeleni are now known: carapace ( Figs 2B ; 5D), chelae ( Figs 2 ; 3A ; 5E), P2-P5 ( Figs 2 ; 4 ; 5A), mxp3 ( Figs 2 ; 3A, B ; 5A), thoracic sternum ( Figs 3A, C, F ; 5A-C), and male and female abdomens ( Fig. 3A, C, F ). The male abdomen is only slightly narrower than the female one; it seems to have a wider segment 6 than in the female; the telson is short and semi-circular in males, more elongate and triangular in females. In both sexes, there are three small transverse ridges on each abdominal segment, not aligned on segment 6 (one on the median part, and two at the lower margin). Two marked tubercles are present medially on the long sternite 4 of several Mexican and Colombian specimens. The reduced and thin P5 is preserved in a number of specimens ( Figs 2B ; 4E, F ).

According to Stenzel (1945), characters distinguishing C. vanstraeleni from C. inflatus concern only the number of tubercles on the longitudinal rows of the dorsal carapace. As that number is not constant between specimens of C. vanstraeleni (from Texas, for example) and in the absence of more complete material of C. inflatus , the idea that all this material could belong to a single widely distributed species (with records from France, Germany, Israel, Texas, Mexico and Colombia) during the Albian-Turonian cannot be ignored. Nevertheless, C. inflatus and

C. vanstraeleni show some differences in the dorsal tubercles and curvature of the epibranchial ridge; in addition, the front seems to be less produced in C. vanstraeleni .

A huge and three-dimensionally-preserved female specimen (carapace 160 × 150 mm, estimated measurements, not including spines) from Colombia, known by chelae, subhepatic and pterygostomian regions, partially exposed thoracic sternum, and wide, unfolded abdomen ( Fig. 6A, B ), is herein referred as Cenomanocarcinus aff. vanstraeleni . Sternite 6 is devoid of a vulva, which confirms its status as a non-eubrachyuran crab. Similarly, other isolated sterna interpreted to presumably belong to females do not show vulvae on sternite 6. Each episternite 5 shows a pair of prominences which is blunt, weathered, but well preserved and recognisable on left side (crab seen by ventral view). This pair of prominences is assumed to be a part of the abdominal holding system.

The sternum (associated with a carapace) of a smaller Cenomanocarcinus from the upper Albian of Colombia (Vega et al. in study) shows a crownshaped plate (at least sternites 2 and 3), long sternite 4, and deep, curved sutures 4/5 ( Fig. 3E ).

Both abundance and completeness of the fossils available for the present study provide critical information and ample evidence to erect a new family.

SPECIES POSSIBLY SYNONYMOUS WITH

EITHER CENOMANOCARCINUS VANSTRAELENI

OR C. INFLATUS

Ophthalmoplax spinosus Feldmann, Villamil & Kauffman, 1999 ( Feldmann et al. 1999: 96, figs 3, 4) From the upper lower Turonian of Colombia, assigned to the Carcineretidae Beurlen, 1930 (see Vega et al. 2001: 323; Feldmann & Villamil 2002: 718), O. spinosus has recently been placed by Vega et al. (2007: 412, 414) in the synonymy of C. vanstraeleni . We agree that O. spinosus may be a species of Cenomanocarcinus , notably in respect to its thoracic sternum being completely filled by the abdomen, and the enlarged propodi of P3-P4. New material (two deformed specimens) from Colombia found at the same locality and stratigraphic unit (San Rafael Formation) examined by one of us (FV) shows

mxp3, P4 and sternum to be similar to those found in specimens of C. vanstraeleni from Mexico ( Vega et al. 2007: figs 8.10, 8.11). However, with only the two deformed specimens available, it is not possible to verify the precise status of O. spinosus .

Contrary to the Cenomanocarcinidae n. fam., the extinct eubrachyuran (heterotreme) family Carcineretidae – in referring only to the ventral features – shows a wide thoracic sternum and a deep sterno-abdominal cavity laterally bordered by a broad sternal portion, as in Carcineretes planetarius Vega, Feldmann, Ocampo & Pope, 1997 (Vega et al. 1997: 320, figs 2-5), Ophthalmoplax triambonatus Feldmann & Villamil, 2002 ( Feldmann & Villamil 2002: fig.4.2), or as in O. stephensoni Rathbun, 1935 ( Schweitzer et al. 2007: fig. 1b, g). In all these species, P5 are not reduced and exhibit ovate articles; articles of both P4 and P5 are modified, P4 with a flattened carpus and merus, P5 with paddle-like propodi and dactyli ( Schweitzer et al. 2007: 19). Modification of P3 as in Cenomanocarcinus vanstraeleni ( Figs 2 ; 4 ; 6A ) is not yet known.

Carcineretes sp. ( Neumann & Jagt 2003: 162, fig. 1) From the lower Turonian of Germany, attributed to Carcineretes with a query, it shows actually, posteriorly to the huge chelipeds, only three pairs of long appendages, here interpreted as P2 to P4. The specimen thus appears to belong to a species of Cenomanocarcinus despite the merus, carpus, propodus and dactylus of P5 (in reality P4) having been described as flabelliform.

Cenomanocarcinus hierosolymitanus Avnimelech, 1961 ( Avnimelech 1961: 1-3, figs 3, 4)

From the upper Cenomanian (Neolobites horizon) of Jerusalem, Israel, represented by an incomplete carapace, C. hierosolymitanus was previously identified as C. cf. vanstraeleni by Remy & Avnimelech (1955: 314) on the basis of an incomplete specimen. The carapace is subcircular in outline and lacks a “hepatic” (?epibranchial) ridge. The differences used to introduce a new species fall within the intraspecific variation of C. inflatus . The species was attributed provisionally ( Larghi 2004: 534) to Corazzatocarcinus Larghi, 2004 (type species:

Geryon hadjoulae Roger, 1946 ), a genus suspected

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

to have podotreme affinities ( Roger 1946; Larghi 2004: 530; Vega et al. 2007: 412, 417). The precise status of Corazzatocarcinus is problematic.

Figures

FIG. 2. — Cenomanocarcinus vanstraeleni Stenzel, 1945, Turonian, Eagle Ford Group, Múzquiz, Coahuila, Mexico: A, female (MUZ- 211), ventral view, see chelae, slender P2, and P3 and P4 with inflated propodi; B, female (MUZ-208), dorsal view, see reduced P5 visible on both sides (see Figure 4E, F). Scale bars: 10 mm.

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. 4. — Cenomanocarcinus vanstraeleni Stenzel, 1945, Turonian, Eagle Ford Group, Mexico, Múzquiz, Coahuila: A, female (MUZ- 209), P2 and P3; B, female (MUZ-204), P3; C, female (MUZ-216), P4 with inflated propodus; D, female (MUZ-246),narrow P2, P3 and P4 with inflated propodi; E, F, female (MUZ-208), reduced P5. 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.