Eur. J. Entomol. 101: 145-151,2004 ISSN 1210-5759 A new Upper Cretaceous species of Chresmoda from Lebanon - a latest representative of Chresmodidae (Insecta: Polyneoptera inc. sed.): first record of homeotic mutations in the fossil record of insects ANDRE NEL 1 , DANY AZAR 2 , XAVIER MARTINEZ-DELCLOS 3 and EDOUARD MAKHOUL 4 'Laboratoire d'Entomologie and CNRS UMR 8569, Museum National d'Histoire Naturelle, 45 Rue Buffon, F-75005 Paris, France; e-mail: anel@mnhn.fr 2 Lebanese University, Faculty of Science II,, Biology Department, Fanar - Matn - B.P. 26110217, and Saint-Joseph University, Campus of Sciences and Technology, MarRoukos (Mkalles), B.P. 11-1514 Beirut, Lebanon; e-mail: azar@mnhn.fr 3 Departament d'Estratigrafia, Paleontologia i Geociencies Marines, Facultat de Geologia, Universitat de Barcelona, E-08071, Barcelona, Spain; e-mail: xdelclos@geo.ub.es "Saint-Joseph University, B.P 165507, Beyrouth, Lebanon; e-mail: maked@cyberia.net.lb Key words. Insecta, Polyneoptera, Chresmodidae, Cenomanian, Lebanon, systematic palaeontology, Palaeoecology, leg morphology, pleustonic life Abstract. The most recent representative of the semi-aquatic insect family Chresmodidae is described from the Lebanese Cenoma- nian marine lithographic limestone. Its highly specialized legs, with a high number of tarsomeres, never observed in other orders of insects, were probably adapted for water surface skating. We hypothesize the occurrence of a unique, extraordinary "antenna" muta- tion affecting the distal part of the legs of the Chresmodidae, maybe homeotic or affecting some genes that participate in the leg development and segmentation. The Chresmodidae had a serrate ovipositor adapted to endophytic egg laying in floating or aquatic plants. They were probably predaceous on nektonic small animals. As the Chresmodidae and the aquatic water skaters of the bug families Veliidae and Gerridae were contemporaneous during at least the Lower Cretaceous, these insects'probably did not cause the extinction of this curious group. The Mid Cenomanian "fish beds" of Nammoura, Leba- non, contain a rich and diverse fauna of marine fishes, aquatic and terrestrial reptiles, bird remains, some small crustaceans (Schram et al., 1999), cephalopods, copro- lithes and small fecal pellets. A well-preserved plant assemblage was also described, with aquatic ferns, gym- nosperms, and angiosperm flowers and leaves (Krassilov & Bacchia, 2000). Despite the presence of these terres- trial plant remains in this "lithographic" limestone, no insect was recorded from this outcrop, except for an indi- cation of the presence of a beetle, not confirmed yet. One of us (E.M.) has found recently three well-preserved chresmodid larval exuviae and another larva, which we describe now. These fossils are the most recent Chresmo- didae and its first record for the Middle East. They are of great interest for the palaeoautoecology and palaeobioge- ography of this enigmatic group and the reconstruction of the palaeoenvironment of the Nammoura "fish beds". Family Chresmodidae Handlirsch, 1908 Polyneoptera of uncertain position (after Rasnitsyn, 2002) Type genus. Chresmoda Germar, 1839. Type species. Chresmoda obscura Germar, 1839 (Tithonian, Upper Jurassic, lithographic limestone, Solnhofen, Germany). Other species. Chresmoda aquatica Martinez-Delclos, 1989 (Barremian, Rasnitsyn & Martinez-Delclos, 2000, Montsec, Lleida, Spain); Chresmoda orientalis Esaki, 1949 (Early Creta- ceous, Rasnitsyn, 2002, Lingyen-hsien, Jehol Province, China); Chresmoda libanica sp. n. The Chresmodidae are also present in the Aptian Santana palaeolake (Brazil) (Bechly, pers. comm.), and in the Middle or Late Jurassic of Bakhar in Mongolia (Rasnitsyn, 2002). Other genus. Saurophthiroides Ponomarenko, 1986. Chresmoda libanica sp. n. Figs 1-14 Material. Holotype specimen NI 3a-b, paratypes specimens NI la-b, NI 2a-b, and NI 4 (Nammoura Insect), collection Edouard Makhoul, Beyrouth, Lebanon. Type locality. Nammoura, El Ghabour valley, Caza Kes- rouane, Mouhafazit Jabal Loubnan (Mont-Liban district), Leba- non. Stratigraphic horizon. Mid-Cenomanian, Upper Cretaceous. Etymology. After Lebanon. Diagnosis. Differing from other Chresmoda spp. in the following characters: prothoracic tibia very short, repre- senting 23% of femoral length; tarsi with a high number of tarsomeres, about 18 in prothoracic legs and more than 40 in meso- and metathoracic legs. Description. Specimens NI 1, NI 2, and NI 4 are nym- phal exuviae because their thoraces are dorsally opened. Specimen NI 3 is a nymph visible from ventral surface. NI 4 is smaller than the other specimens and has no visible ovipositor (younger nymph or male specimen?). Body 13.0 mm long (including ovipositor), 5.4 mm wide (NI 3), 9.5 mm long, 4.0 mm wide (NI 2), 11.6 mm long, 4.8 mm wide (NI 1>; 4.0 mm long, 2.8 mm wide (NI 4). The heads are poorly preserved, 2.3 mm long, 2.4 mm wide (NI 3). Two structures are visible, 0.8 mm long and 145