Bollettino del Museo Civico di Storia Naturale di Verona, 33, 2009 Botanica Zoologia: 105-112 Haploginglymus morenoi (Crustacea, Amphipoda, Niphargidae) a new interstitial Iberian species with unusual maxilliped VALENTINA IANNILLI*, ALESSANDRO MINELLI**, SANDRO RUFFO*** (*Dipartimento di Biologia Animale e dell’Uomo, Università di Roma “Sapienza”, **Dipartimento di Biologia, Università di Padova, ***Museo Civico di Storia Naturale di Verona) Abstract We describe here Haploginglymus morenoi n.sp. (Amphipoda Gammaridea Niphargidae) from the freshwater interstitial environment along Rio Mataraña, Beceite (Aragón), North-Eastern Spain. Sediment in the type locality is very ine-grained. Peculiar to the new species is article 6 of the maxilliped palp, which is spoon-like, with inely ciliated distal margin, rather than having the usual shape as a dactylus provided with a claw. Further diagnostic characters are provided by the sexually dimorphic gnathopods II and by the very elongated dactylus of pereiopods 6 and 7, whose claw is extremely short. One of the specimens of the type series is anomalous, in that its maxilliped has a pretty normal left dactylus, the right one being however shaped as in the other specimens of this species. Key words: Haploginglymus morenoi n. sp., interstitial environments, transformed maxilliped, saltationary evolution. Riassunto Si descrive Haploginglymus morenoi n. sp. (Amphipoda Gammaridea, Niphargidae) dell’ambiente interstiziale del Rio Mataraña, Beceite (Aragón), Spagna nordorientale; il sedimento del locus typicus è costituito da granuli inissimi. La nuova specie si distingue in particolare per il maxillipede che presenta l’articolo 6 del palpo, che normalmente si presenta negli Anipodi come dattilo provvisto di un unghia, trasformato nella nuova specie in una paletta espansa e concava, a guisa di cucchiaio, con il margine distale inemente ciliato. Altri caratteri distintivi sono negli gnatopodi 2, sessualmente dimorici, e nel dattilo molto allungato dei pereiopodi 6-7, con unghia estremamente corta. Nella serie tipica un esemplare anomalo presenta sul lato sinistro il maxillipede con dattilo quasi normale mentre il suo equivalente sul lato destro risulta, invece, trasformato in una paletta. Parole chiave: Haploginglymus morenoi n. sp., ambiente interstiziale, maxillipede trasformato, discontinuità evolutive. Introduction In the spring of 1998, during a collecting trip to North-Eastern Spain (Aragón), our friend Reinhard Gerecke from Tübingen (Germany), the well-known specialist of freshwater mites, collected in the intersti- tial environment along Rio Mataraña, Beceite (Aragón) four specimens of an amphipod species, likely belonging to the Niphargidae, conspicuous for the very unusual shape of their maxilliped. Unfortunately, the material did not allow for a safe identiication to the genus level because of the lack of some appendage pairs, in parti- cular uropods III, which are required to discriminate between Niphargus and Haploginglymus. he collector informed us that sampling of interstitial fauna at that site was far from easy because of the very ine-grained nature of sediments. However, following his advice we contacted dr. Josè Luis Moreno Alcaraz of the Centro Regional de Estudio del Agua, Universidad de Castilla-La Mancha, Albacei- te, who kindly sent us four additional specimens from a nearby site that provided evidence that the new species is a representative of genus Haploginglymus. Taxonomy Haploginglymus morenoi n. sp. (Fig. 1 – 4) Material examined 4 specimens (paratypes, on slides nr. 6981-6984), E 134, rio Mataraña, Beceite, Aragón, Spain, 40°50’N, 0°11’E, 600 m, interstitial, 18.04.1998, leg. R. Gerecke; 4 specimens (1 holotype, 3 paratypes) Valdeltormo, Aragón, Spain, 40°59’9”N, 0°6’44”E, leg. J.L. Moreno Alcaraz, at depth 30 cm. Conductivity 473μS/cm; water temperature 15.9°C; dissolved oxygen 10,9 mg/l, 117%; pH 8,6. Accompanying hyporheic fauna: Ephemerop- tera, Plecoptera, Hydracarina, Copepoda, Ostracoda (1