Phylogeny, taxonomy and nomenclature:the problem of taxonomic categories and of nomenclatural ranks

............................................................................................................................................................................27 Introduction .......................................................................................................................................................................28 Ranks and nominal-series in zoological nomenclature ..................................................................................................... 29 The problem of equivalence between taxa of the same nomenclatural rank .................................................................... 31 The confusion between nomenclatural ranks and taxonomic categories ..........................................................................35 The usefulness of nomenclatural ranks in taxonomy........................................................................................................ 38 Clarity and ambiguity in the meaning of nomina ..............................................................................................................39 Systems of allocation of nomina to taxa, monosemy and polysemy ................................................................................41 Extensional definitions of nomina ............................................................................................................................. 41 Intensional definitions of nomina ..............................................................................................................................42 Ostensional allocation of nomina to taxa ...................................................................................................................44 Discussion .........................................................................................................................................................................46 The distinction between nomenclatural ranks and taxonomic categories ..................................................................46 Compulsory and optional nomenclatural ranks ......................................................................................................... 48 Should the Code be fundamentally modified to become fully monosemic? .............................................................50 The need of clarifications in the Code .......................................................................................................................52 Phylogenetic definitions of taxa and the Code ...........................................................................................................52 Conclusion .........................................................................................................................................................................54 Acknowledgements ...........................................................................................................................................................55 References .........................................................................................................................................................................55 Appendix. Cladognoses, apognoses and diagnoses: the example of the family Megophryidae (Amphibia, Anura) .......60