Lithophylax trigeri A. Milne-Edwards & Brocchi, 1879 from the French Cretaceous (Cenomanian) and placement of the family Lithophylacidae Van Straelen, 1936 (Crustacea, Decapoda, Brachyura) Danièle GUINOT Département Milieux et Peuplements aquatiques, Muséum national d’Histoire naturelle, case postale 53, 57 rue Cuvier, F-75231 Paris cedex 05 (France) [email protected] Gérard BRETON Laboratoire Géosciences, Université de Rennes I, campus de Beaulieu, 263 avenue du Général-Leclerc, F-35042 Rennes cedex (France) [email protected] Guinot D. & Breton G. 2006. — Lithophylax trigeri A. Milne-Edwards & Brocchi, 1879 from the French Cretaceous (Cenomanian) and placement of the family Lithophylacidae Van Straelen, 1936 (Crustacea, Decapoda, Brachyura). Geodiversitas 28 (4) : 591-633. Abstract Based on numerous and remarkably preserved specimens from the Upper Cre- taceous, Cenomanian, at Lamnay and Le Mans (Sarthe), France, the fossil crab Lithophylax trigeri A. Milne-Edwards & Brocchi, 1879 is redescribed. Characters which were thought not to be easily fossilized (rostrum, vulvae, female and male abdomen, male pleopods, thoracic sternal sutures, stridulating apparatus and the reduced fifth pereopod) are present. It was possible by careful clearing of the fossil crab from the matrix to expose most of the parts, so that the structures could be studied almost as completely as in a recent species. Lithophylax trigeri is Key words Crustacea, one of the most complete brachyuran crabs so far discovered from the Cenoma- Brachyura, nian, from the Cretaceous in general, and even more recently. The monotypic Lithophylacidae, Lithophylax, family Lithophylacidae Van Straelen, 1936 is redefined, and its relationships stridulating apparatus, with the fossil and extant brachyuran families known from the Cretaceous, in Cretaceous, particular the Carcineretidae Beurlen, 1930, Necrocarcinidae Förster, 1968, Cenomanian, Maine (France), Hexapodidae Miers, 1886, Retroplumidae Gill, 1894, Palicidae Bouvier, 1897, taphonomy. and the Goneplacidae MacLeay, 1838, are discussed. GEODIVERSITAS • 2006 • 28 (4) © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris. www.geodiversitas.com 591 Guinot D. & Breton G. Résumé Lithophylax trigeri A. Milne-Edwards & Brocchi, 1879 du Crétacé de France (Cénomanien) et statut de la famille des Lithophylacidae Van Straelen, 1936 (Crustacea, Decapoda, Brachyura). Grâce à la découverte de nombreux spécimens remarquablement préservés du Crétacé supérieur (Cénomanien), trouvés en France à Lamnay et au Mans (Sarthe), le crabe fossile Lithophylax trigeri A. Milne-Edwards & Brocchi, 1879 est redécrit. Plusieurs structures (rostre, vulves, abdomen femelle et mâle, pléo- podes mâles, sutures sternales thoraciques, appareil de stridulation, et dernier péréopode, réduit), supposées ne pas se fossiliser aisément, sont présentes. Un minutieux dégagement a permis d’exposer la plupart des régions du crabe, si bien que son organisation a pu être étudiée presque aussi complètement que Mots clés chez une forme actuelle. Lithophylax trigeri est l’un des Brachyoures les plus Crustacea, complets découverts à ce jour, du Cénomanien, du Crétacé en général, voire Brachyura, plus récemment. La famille monotypique des Lithophylacidae Van Straelen, Lithophylacidae, Lithophylax, 1936 est redéfinie, et ses affinités avec les familles brachyouriennes actuelles et appareil de stridulation, éteintes connues depuis le Crétacé, en particulier les Carcineretidae Beurlen, Crétacé, 1930, Necrocarcinidae Förster, 1968, Hexapodidae Miers, 1886, Retroplumi- Cénomanien, Maine (France), dae Gill, 1894, Palicidae Bouvier, 1897 et les Goneplacidae MacLeay, 1838, taphonomie. sont discutées. Table of contents Introduction ............................................... 593 Other brachyuran crustaceans reported from Abbreviations .......................................... 593 the stratotypic Cenomanian with Lithophylax Occurence and stratigraphy ........................ 594 trigeri ...................................................... 608 Middle-upper Cenomanian ..................... 594 Discussion ............................................... 610 Lower Cenomanian ................................. 595 Lithophylacidae vs Carcineretidae Beurlen, Material examined and prepared ................. 595 1930 ....................................................... 612 Middle-upper Cenomanian material ....... 595 Lithophylacidae vs Necrocarcinidae Förster, 1968 Lower Cenomanian material ................... 596 and Orithopsidae Schweitzer, Feldmann, Fam, Method ...................................................... 596 Hessin, Hetrick, Nyborg & Ross, 2003 ... 615 Taphonomy ................................................ 597 Lithophylacidae vs Hexapodidae Miers, 1886 .. Cuticular structure .................................. 597 ................................................................ 617 Petrography of the nodules ...................... 598 Lithophylacidae vs Retroplumidae Gill, 1894 .. Paleoecology and ethology .......................... 600 ................................................................ 618 Systematics ................................................. 600 Lithophylacidae vs Palicidae Bouvier, 1898 ..... Family Lithophylacidae Van Straelen, 19366 ... ................................................................ 620 ................................................................ 600 Lithophylacidae vs Goneplacidae MacLeay, Genus Lithophylax A. Milne-Edwards & Brocchi, 1838 ....................................................... 620 1879 ....................................................... 602 Conclusion ................................................. 622 Lithophylax trigeri A. Milne-Edwards & Brocchi, Acknowledgements ..................................... 623 1879 ....................................................... 602 References .................................................. 623 Remarks on the stridulating apparatus .... 607 Annexe ....................................................... 631 592 GEODIVERSITAS • 2006 • 28 (4) Lithophylax trigeri and placement of Lithophylacidae Introduction or goneplacid, or portunid, or carcineretid with more agreement. Abundant material of the rare and not well known The present paper reports on exceptionally well fossil crab, Lithophylax trigeri A. Milne-Edwards & preserved specimens of Lithophylax, where most Brocchi, 1879, was collected by one of us (GB) from parts were rescued by gently removing the matrix the Upper Cretaceous (Cenomanian) of France in in several individuals. The under parts were vis- the Louvre quarry, Lamnay (Sarthe, France). Several ible after the matrix was removed. Male pleopods, specimens of the same species, from the stratotypic vulvae, and the reduced fifth pereopod, characters middle-upper Cenomanian of Le Mans (Sarthe), that are believed not to be readily fossilized, were were also discovered in the collections of several present. The antennular and antennal regions, and institutions. the distal part of the eyes were unfortunately not The genus Lithophylax was established by A. Milne- preserved. A spectacular stridulating apparatus has Edwards & Brocchi (1879: 116) for L. trigeri col- been found and prepared. It was possible to study lected by J. Triger in the “Grès verts du Maine” the external structures of Lithophylax almost as (Cenomanian Greensand of the Maine: terminology completely as in a recent species. Lithophylax trigeri in Rathbun 1935: 57). The same species was also proved to be one of the most complete crabs so far collected in the same place by Guéranger but not discovered from the Cenomanian, and even from published in his 1867 papers. A. Milne-Edwards the Cretaceous. The partial elimination of the abdo- & Brocchi (1879), based on males and females, men, which allowed the observation of the vulvae characterized the species as having a transversally and gonopods, clearly allowed its placement in the hexagonal carapace, extremely narrow front, and Heterotremata Guinot, 1977. large and bipartite orbits that implied particu- Slight morphological differences between lower larly well developed eyes, presumed to be carried Cenomanian and middle-upper Cenomanian mate- on angled stalks. No figure was provided. The rial seem to be not regarded as specific and are not genus was assigned to the “tribu Gonéplaciens” sufficient to warrant naming it a new species. H. Milne Edwards, 1837 (Goneplacidae MacLeay, 1838). Lithophylax trigeri was again quoted as ABBREVIATIONS “rather frequent” by Guillier (1886: 238, 244) in A1-A6 abdominal segments (or somites) 1 to 6; the “Sables supérieurs à Rhynchonella compressa” G1 first male pleopod or first gonopod; G2 second male pleopod or second gonopod; (middle-upper Cenomanian) of the Sarthe De- LC lower Cenomanian material; partment. Juignet (1974) provided a history and L/W length/width; synonymy of the stratigraphic units of the Ceno- MUC middle-upper Cenomanian material; manian stratotype. mxp3 third maxilliped; Lithophylax trigeri was not recorded for a long time. P1-P5 first to fifth pereopods; 1/2-7/8 thoracic sternal sutures 1/2 to 7/8. A new record from the same geologic formations (“Sables à Rhynchonella compressa”) was given by Van The material used in this study is deposited in the fol- Straelen (1936: 43, pl. 4, fig. 9), who presumably lowing institutions: saw the original material of A. Milne-Edwards & MHNH Muséum d’Histoire naturelle, Le Havre Brocchi and established a separate family, the