A revision of the Pliocene and Quaternary Lutrinae from Europe

In this paper, a revision of the Pliocene and Quaternary Lutrinae from Europe is presented. Such a revision, including fossil material, has not been published since the work of Pohle (1919). Three tribes within the Lutrinae are recognized: the Lutrini, the Aonyxini and the Enhydrini. The latter comprises both Enhydra and the Enhydriodon group. The genus Nesolutra, consisting of three insular species, is not retained. Two are included in Lutra and for N. ichnusae a new genus, Sardolutra, is proposed. The genus Isolalutra is not retained either. Its only species, I. cretensis, is included in the genus Lutrogale. Some new material of this species is described. A number of well-preserved fossils of Cyrnaonyx antiqua are described, such as the hitherto unknown skull and upper carnassial as well as postcranial material from Tornewton Cave. The systematic position of the species and genus is reviewed in detail. A new specimen of Enhydra reevei from Bramerton is described. The morphology of the M1 supports the inclusion of the species in Enhydra. The functional morphology and the ecology of the reviewed species is discussed and compared to extant lutrines. Adaptations in the postcranial skeleton indicate a very aquatic way of life for Lutra simplicidens, L. trinacriae, L. euxena and, to an even greater extent, Sardolutra. Lutrogale cretensis on the contrary shows a more terrestrial adaptation. Cyrnaonyx shows adaptations similar to Lutra and probably was a stream dweller, thus differing from its extant relative Aonyx. From the dentition and the endocranial cast, conclusions on the feeding habits are drawn. The described Lutra and Sardolutra species were probably all specialized on motile prey, viz. fish. Lutrogale, Algarolutra, Megalenhydris and Cyrnaonyx show adaptations to a mixed diet, consisting of both fish and shellfish, though differences in the feeding habits between those forms are noted also. Enhydra reevei probably fed on shellfish exclusively. In the last part, the phylogeny and palaeogeography of the Lutrinae are discussed. It is argued that the oldest Lutrinae, Mionictis spp., originated from the Melinae. The phylogeny of the Lutrini can be reconstructed relatively well. The ancestry of the island forms in the Mediterranean is discussed in some detail. For the Aonyxini, the fossil record is rather poor and a reconstruction of the phylogeny is virtually impossible. The origin of Cyrnaonyx is uncertain and the ancestry of Megalenhydris is unknown. The origin of the Enhydrini is somewhat obscure. The group reached a wide distribution and gave rise to the Enhydra line. The relationships between the species are discussed. The problems involved in island species are considered. Remarks on the presence of otters in unbalanced island faunas are made. The peculiar taphonomy of otter fossils on islands is noted.