CretaceousResearch (1991) 12, 553-560
A new late Maastrichtian xanthid crab from southern Limburg (The Netherlands)
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J. W. M.
Jagt, t J. S. H. Collins & $ R. H. B. Fraaye
* Tweeo!eMaasveldstraat 47, NL-5921 JN Venlo, The Netherlands f 63 Oakhurst Grove, East Dulwich, Ladon SE22 9AH, UK ,tGeoCentrum Brabant, St Lambertusweg 4, NL-5291 NB Boxtel, The Netherlands Received 18Jantuq
1991 and accepted 4 April 1991
A new species of xanthid crab, Xanthosia semiomuta, and claw fragments placed, with reservation, in Aukopodia rienmfyki Bosquet, 1854, are described from the late Maastrichtian Meerssen Member (Maastricht Formation) in the type area of the Maastrichtian Stage, SE Netherlands. KEY WORDS:
Netherlands; late Maastrichtian; decapod crustaceans; Xanthosia semiornata sp. nov.
1. Imoduction The decapod fauna of the Campanian-Maastrichtian strata in the type area of the Maastrichtian Stage (the area between Maastricht, Liege and Aachen) (Figure 1) is still rather poorly known, and quite a number of species that have been described previously are in need of revision. Amongst the crabs, various species have been recorded, and recent stratigraphic collecting has yielded numerous specimens (lithostratigraphic terminology of Felder, 1975). Several specimens of the new species described and illustrated herein were collected by the authors from the Meerssen Member of the Maastricht Formation, as exposed at the Ankersmit Holding B.V. quarry (formerly Nekami) and at the ENCI N.V. quarry (Maastricht), and are of late (but not latest) Maastrichtian age.
2. Stratigraphy The holotype of the new species was collected from a large block of coarse-grained bryozoan biocalcarenite, characteristic of the lower part of the Meerssen Member (Maastricht Formation) as exposed in the Ankersmit Holding B.V. quarry (formerly Nekami, ‘t Rooth) at Bemelen, province of Limburg, some 4 km west of Maastricht (Figure 1). This is outcrop no. 62A-7 of the files of the Geological Survey Heerlen: topographical map of the Netherlands 1: 25,000, sheet 62A Valkenburg aan de Geul, co-ordinates 182.500/316.500. Owing to quarrying activities, this block had recently fallen from the top of the section exposed; a subsequent analysis of its bioclast content by P. J. Felder (pers. comm., May 1990) confirmed its provenance from the lowermost metre of the Meerssen Member. The paratypes were collected from the lower Meerssen Member (see Figure 2) as exposed at the ENCI N.V. quarry, the stratotype of the Maastrichtian Stage, and comprise two carapaces. Coincident on the block with one of the paratypes of the new species are two fragmentary chelae (MAB k.0023 and k.0024); their xanthid affinity is doubtful and there are certain propensities towards 0195~6671/91/060553 + 08 $03.00/O
@ 1991 Academic Press Limited
Figure 1. Simplified map of the Maastrichtian Campanian-Maastrichtian.
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type area (southern Limburg and adjacent Belgian and German territory) showing key localities of the Liege-Limburg
A new late Maastrichtian xanthid crab
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Aulacopodia
riemsdyki Bosquet, which influence us to place them tentatively with that species. In Figure 2, lithologic logs of three important sections (Ankersmit Holding B.V./Bemelen, Blom/Berg en Terblijt and ENCI N.V./Maastricht) are presented and the stratigraphic provenance of recently collected decapod species indicated. These data are of a preliminary nature; studies under way will undoubtedly contribute to refining this picture.
3. Systematic descriptions Section Brachyrhyncha Borradaile, 1907 Superfamily Xanthoidea Dana, 1852 Family Xanthidae Dana, 1852 Genus Xanthosia Bell, 1863 Type species-Xanthosia gibbosa Bell, 1863 (p. 3, pl. 1, figs 4-6) = Podophthalmus bwhii Reuss, 1845 (see Wright & Collins, 1972, p. 93) by subsequent designation of Glaessner (1929, p. 401). Xanthosia semiarnata sp. nov. Figures 3A-F. Diagnosis.
Carapace sub-hexagonal in outline, almost flat in both longitudinal and transverse sections; the anterior part of protogastric lobe, hepatic region, epi- and mesobranchial lobes ornamented with numerous sub-spherical tubercles. Derivation ofname. In allusion to the arrangement of the surface ornament. Material. The left-hand half of a carapace, holotype, late Maastrichtian Meerssen Member (Maastricht Formation), Ankersmit Holding B.V. quarry, Bemelen. Collection GeoCentrum Brabant, no. MAB k.0020 (leg. J. W. M. Jagt). Paratypes are carapaces MAB k.0021, and MAB k.0022, both from the Meerssen Member (Maastricht Formation), ENCI N.V. quarry, Maastricht (see Figure 2). Destiption. The carapace is subhexagonal in outline, length about half the breadth; it is flatly arched longitudinally and in transverse section it is almost flat medially and gently inclined at the margins. The orbitofrontal margin occupies rather more than two thirds of the carapace width. The front is broadly triangular with concave sides and slightly extended beyond the orbits; a deep median sulcus divides around the apex of the anterior mesogastric process. An incipient notch separates the front from a triangular inner orbital spine and the upper orbital margin is thin with two short notches. There is a pair of even-sized nodes on the rostra1 side of the margin, and the margin lateral to the outer orbital spine is sharp. The orbits are large, almost circular and forward facing. The anterolateral margin is gently rounded and armed, behind the outer orbital spine, with two rounded-triangular teeth (the one behind being the larger), separated from each other by a deep concave notch. The widest part of the carapace is at the epibranchial angle and the epibranchial lobe has a rounded spine with a small, rather more triangular one behind. The posterolateral margin is weakly concave in its upper part and concave in its lower part; it leads by way of a sharp posterior angle to shallow coxigeal embayments almost in line with the weakly concave posterior margin. Short hepatic furrows lead to a broad, postorbital depression. The cervical furrow is sinuous and almost transverse; narrow where it crosses the midline rather more than half the distance from the front, it becomes broad and shallow to the hepatic furrow, then deepens towards the margin. In contrast, the branchiocardiac furrows are vaguely defined; from a distinct pore,
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Figure 3A-F. Xunthosia semtitu sp. nov. Holotype (A-D) and paratypes (E, F). Collection GeoCentrum Brabant Boxtel (MAB k.0020, 0021 and 0022, respectively), views of carapaces, and composite picture (D), restoring the missing right-hand part of the holotype carapace, x2.5 (A-D, F) and x 2.0 E). G, H. Claws (MAB k.0023 and 0024, respectively) tentatively placed with Atdmopodti riemdyki Bosquet, 1854, found with paratype carapace MAB k.0021. Left-hand chela, inner surface (k.0023) and right-hand chela, outer surface (k.O024), x 2.0 and x 2.8, respectively.
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anterior branches run towards the cervical furrow lateral to the hepatic furrow and posterior branches run towards the posterior margin of the cardiac region. The anterior mesogastric process is broadly triangular and well-defined, it terminates some distance from the front level with the upper orbital margins, and a pair of granules at the base of the process separates it from the less well-defined mesogastric lobe. The urogastric lobe is more than twice as wide as it is long. It is separated from the cardiac region only by short lateral grooves, and a small median extension penetrates the base of the mesogastric lobe. The cardiac region is pentagonal with deeply excavated margins. Narrow, triangular epibranchial lobes are partially separated by a short furrow from the mesobranchial lobes. Clusters of sub-spherical tubercles crowd the rostra1 area, the anterior part of the protogastric lobes, the hepatic regions, and epi- and mesobranchial lobes. The largest of these tubercles occurs anteriorly on the hepatic region, but with this exception the clusters regularly comprise tubercles of two different sizes, with the smaller ones dominating that part of the cluster closer to the midline. The metabranchial lobe is crowded with wide, shallow pits and a number of deeper pits are scattered over the surface, the most conspicuous being the median gastric pits close to the midline and three or four marking the internal mandibular adductor muscles. There are deep muscle pits at the outer angles of the urogastric lobe and deep muscle grooves bounded by a ridge separate the cardiac region from the metabranchial lobes. Discussion. The surface ornament of X. semiornata immediately distinguishes it from any known member of the genus. In the outline of the carapace and arrangement of the lobes, and in particular, the anterior mesogastric process, there is a close resemblance to the Albian-Cenomanian Xanthosia buchii (Reuss, 1845), which also has, albeit very weak, clusters of granules covering much the same areas as on X. semiwnata (see Wright 8z Collins, 1972, pl. 20, fig. 3a); X. buchii differs, however, in being more tumid, the cervical furrow is more even in width, the branchiocardiac furrows are more prominent, and the upper orbital margin is devoid of tubercles. It seems probable that X. buchii was close to the ancestral root, if not the ancestor of X. semiornata. The Albian-Cenomanian Xantkosia similis (Bell, 1863; Wright & Collins, 1972, p. 95, pl. 19, figs 8-12; text-fig. 14~) and Albian Xantkosia aspera Rathbun, 1935 (p. 41) are granulated but the granules are coarser, less regular in size and more generally distributed; carapace outline and surface details further distinguish these species from X. semiornata. The new species would appear to belong to group 2 as distinguished by Secretan (1982, figure 2). Incertae familiae Genus Auhcopodia Bosquet, 1854 Type species-Aulucopodia riemsdyki, by monotypy of Bosquet (1854). ? Aulacopodia riemsdyki Bosquet, 1854 Figures 3G, H. 1854 Aulacopodia Riemsdyki Bosquet, p. 135, pl. 10, fig. 11. 1929 Aulacopodia riemsdyki Bosquet; Glaessner, p. 63. Remarks. The better preserved
of the claw fragments is a left-hand claw (MAB k.0023) viewed from the inner surface: the length of the propodus is rather more than twice the height, highest about mid-length. The upper margin is boldly convex to the almost circular carpal foramen, where it is damaged; the lower margin is continuously, but less strongly rounded and there is a weak concavity at the junction with the fixed finger. The interdigital margin appears to be straight, although there
A new late Maastrichtian xanthid crab
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is a certain amount of impaction from the dactylus. There is a shallow depression before this margin and another extends parallel to the upper margin as far as the carpal foramen. The median area (damaged) is tumid with at least one row of tubercles. There are also two granules on the rounded upper surface. The fixed finger was probably about two thirds of the length of the propodus, proximally ovate in cross-section and with a weak median groove. The upper margin of the dactylus is gently convex, proximally becoming more steeply curved towards the tip which is turned slightly inwards. There are a few pits along the midline and the opposing margin is lined with four or five even-sized, evenly spaced cusps. The other fragment (MAB k.0024) exposes the outer surface of a right-hand claw; the basal margin is almost straight proximally. There is a median groove along the fixed finger and the preserved part of the opposing margin has two large cusps and a smaller one separated by its diameter from the others. Aulumpodia riemsdyki Bosquet was founded on a left-hand claw seen in inner view; it has in common with the present material the relative proportions of height to length of the propodus, the relative length of the dactylus and fixed finger to the propodus, the median groove along the dactylus and fixed finger and the concavity at the base of the fixed finger; also, as far as preserved, the nature and distribution of the cusps lining the opposing margins. Bosquet’s figure lacks the tubercles on the propodus and upper surface, but their absence could be attributed to heterochely; in cases of heterochelous chelae the different claws may occur on either side within the species. Glaessner (1929) who, by placing the taxon in brackets, expressed doubt concerning the status of A. riemdyki, was of the opinion that the claw was possibly dromiid: he did not include the species in the Treatise (Glaessner, 1969). Acknowledgments
Our thanks are extended to E. C. M. J. Schmitz of Ankersmit Holding B.V. (Maastricht) for allowing access to the quarry at Bemelen, to W. M. Felder for assistance during field work, to Dr A. V. Dhondt (Brussels) for items of literature, to P. J. Felder for analyses of bioclast assemblages and to P. H. Kessels (Heerlen) for photographic work. References Bell, T. 1863. A Monograph of the fossil Malacostracous Crustacea of Great Britain, II. Crustacea of the Gault and Greensand. Monograph of the Palaeonwgraphical Soctety of Lundon 14, viii + 4Opp., pls l-10. Borradaile, L. A. 1907. On the classification of the Decapoda. Annals and Magazine of Natural Histoq 19, 4.57-486.
Bosquet, J. 1854. Les Crustaces fossiles du Terrain C&ace du Limbourg. In Ver~mfelingen
uitgegeven door h wmmissie belast met het vervaardigen eener geologische beschrijving en kaurt van Neo!erland, Tweeak &el, pp. 1-127 [lo-1371, pls l-10. (A. C. Kruseman, Haarlem). Dana, J. D. 1852. Crustacea. United States exploring expedition during the years 1838, 1839, 1840,
1841, 1842 under the command of Charles Wilkes, U.S.N., 13, 1620~~. (Philadelphia). Felder, W. M. 1975. Lithostratigrafie van het Boven-Krijt en het Dana-Montien in Zuid-Limburg en het aangrenzende gebied. In Toelichting bij geo&ische overzichtskaarten van Neokrland (eds Zagwijn, W. H. & van Staalduinen, C. J.), pp.63-75 (Rijks Geologische Dienst, Haarlem). Glaessner, M. F. 1929. Crustacea Decapoda. In Fossilium Catalogus (ed. Pompeckji, F. J.) 41, 464~~. (W. Junk, Berlin). Glaessner, M. F. 1969. Decapoda. In Treatise on invertebrate pahxmt&gy (ed. Moore, R. C.), Part R, Arthropoda 4(2), R 399-533, 626-628 (Geological Society of America, Boulder, and University of Kansas Press, Lawrence).
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Rathbun, M. J. 1935. Fossil Crustacea of the Atlantic and Gulf Coastal Plain. Special Paper of the Geological Society of America, 2, vii + 16Opp., 26 pls. Reuss, A. E. 1845-46. Die Versteiwungen der Biihmischen Kreidefonnation, pp.l-58, pls 1-13 (1845); iv+ pp.l-148, pls 14-51 (1846) (E. Schweizerbart, Stuttgart). Secretan, S. 1982. Xanthosiu robertsz, Crustace decapode du C&ace de Madagascar: nouveau nom et nouvelles hypothese sur son origine. Geobios, 15, 927-933. Wright, C. W. & Collins, J. S. H. 1972. British Cretaceous crabs. Monograph of the Pa.!aeontographicul Society of London, 126(533), 1-114, 22 pk.