B.M. LANDAU, F. FRYDMAN & C.M. DA SILVA NOVAPEX 8 (3-4): 111-121, 10 décembre 2007 111 Morum (Oniscidia) domingense from the Caribbean Neogene vs. the Recent M. (O.) lindae: One taxon or two? Bernard M. LANDAU International Health Centres, Av. Infante D. Henrique 7, 8200 Albufeira, Portugal. Centro de Geologia. Universidade de Lisboa. C6. Campo Grande. 1749-016 LISBOA. Portugal. bernielandau@sapo.pt Franck FRYDMAN 3, Rue Charles François Dupuis, 75003 Paris, France. Carlos M. DA SILVA Departamento e Centro de Geologia. Universidade de Lisboa. C6. Campo Grande. 1749-016 LISBOA. Portugal. KEYWORDS. Gastropoda, Harpidae, Morum, Caribbean, Neogene. ABSTRACT. The Morum chipolanum-group of Morum (Oniscidia) species has a long geologic history in Tropical America, although their specimens are never abundant. Most of the original descriptions were based on very few shells. The lack of information concerning intraspecific variability makes classification sometimes difficult within this group of species with somewhat conservative shell design. This study attempts to distinguish several Caribbean Neogene taxa on the basis of combined shell morphometry and qualitative shell characteristics, paying special attention to the distinction between the shells of M. (O.) domingense from the Upper Miocene- Lower Pliocene of the Dominican Republic and those of the Recent M. (O.) lindae from the coasts of Colombia and Venezuela, in order to ascertain if they should be assigned to the same or to distinct taxa. The largest number of specimens yet considered is assembled, drawn from adequately illustrated specimens in the literature, collections and high quality digital photographs posted on the Internet. Analysis shows that by morphometry alone these two taxa cannot be reliably distinguished, but when the morphometric data is considered in combination with other observable shell characteristics the two sets of shells are most likely distinct, actually representing two different taxa. This conclusion is further strengthened by palaeobiogeographical data. INTRODUCTION The genus Morum Röding, 1798, now placed in the family Harpidae Bronn, 1849 (Hughes & Emerson, 1987) superfamily Muricoidea Rafinesque, 1815 (Bouchet & Rocroi, 2005), comprises a small group of species of carnivorous marine gastropods (J. Smith in Beesley et al., 1998), occurring in tropical to subtropical seas worldwide. They are found in shallow to fairly deep waters, but are always uncommon to very rare (J. Smith in Beesley et al., 1998). The subgenus Oniscidia Mörsch, 1852 (= Cancellomorum Emerson & Old, 1963, see Vokes, 1998) comprises a group of Morum species with a cancellate sculpture; for full discussion on the taxonomic problems regarding the name Oniscidia we refer to Beu (1976) and Vokes (1998). In this paper we will only discuss what Vokes (1998) called the M. chipolanum-group of species, characterized by an ornamentation of elongated pustules on the parietal shield as opposed to coarse rugae, as seen in Morum (“Oniscidia”) sp. from the Middle Eocene Gatuncillo Formation (Woodring, 1959) and the Recent Brazilian M. (O.) matthewsi Emerson, 1967. A handful of species belonging to the M. chipolanum- group have been described from the Caribbean Neogene and Recent faunas. The earliest Tropical American records are for the Peruvian M. peruvianum Olsson, 1931 from the Eocene Chira Formation (Olsson, 1931) and for M. (O.) harpula (Conrad, 1848) from the Lower Oligocene Vicksburg group of Mississippi, USA (MacNeil & Dockery, 1984). From the Lower Miocene the following species have been reported: Morum chipolanum Dall, 1925 from the Chipola Formation of Florida, USA and Baitoa Formation of the Dominican Republic (see Vokes, 1998), and M. (Onicidia) jungi Landau, 1996 from the Cantaure Formation of Venezuela (see Landau, 1996). M. harrisi Maury, 1925, from the Lower Miocene Pirabas Limestone of Brazil, is based on internal moulds and its apertural features are unknown (Maury, 1925). Morum (O.) coxi (Trechmann, 1935) occurs in the lower Middle Miocene (Robinson &