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Re: DINOSAUR digest 2977

This thread has wandered far from the mandate of the PhyloCode listserv; given recent issues with the volume of messages on that list, I am only replying to the DinoList.

Mike: please cc me with replies; I get the dinosaur list in digest form, so I find out about replies to my posts a day (or more) after they are sent. :)

Michael de Sosa wrote
But for many fossil genera with only one known species, the generic name HAS traditionally been used for the species. A name like

This is a source of confusion in the literature. Because the Linnaean binominal system requires a genus for every species, many monotypic genus names have been created (especially for fossils). The genus name is always unique, and it is often more efficient to refer to the generic epithet than the whole binomial. This is imprecise, and does not promote taxonomic clarity; if new species are subsequently added to the genus, generalizations about the genus may no longer be valid. The reader must then know how many of the currently referred species are actually included in the genus by the author. This is a general taxonomic problem not restricted to genera, but it can be perhaps most keenly felt there. I suggest that the more reasonable approach is to always reference statements to the most exclusive taxon to which they may be confidently referred, even if this means spelling out a binomial.

There is a similar problem with referring specimens to Genus sp. when the genus in question is monotypic. By implication, this would be a species that conforms to the generic diagnosis, but differs in the specific diagnosis but since both diagnoses are the same for monotypic taxa, the statement is meaningless. If more species are added to the genus, the status of Genus sp. becomes even more murky, because diagnosis of the genus changes. The use of open nomenclature ("cf." or "aff.") gets around this by making what you mean reasonably clear. cf. Genus or cf. (monotypic) Genus species implies uncertainty, whereas Genus sp. implies certainty in placement at the genus level but not the species level.

Regardless, I disagree with your premise: traditional taxonomists use the genus name for a GENUS, not a species. The fact that that genus includes only one species is irrelevant. I know this is a hard concept to swallow... that's part of the problem with ranks. :)

There is an additional "danger" in converting genus names for species. In some cases (e.g., Melanosuchus [Crocodylia: Alligatoridae]) there is only one extant member of a genus, but fossil members have been named. I suspect that many neontologists do not keep such fossil taxa in the forefront of their mind, and might forget them when erecting a phylogenetic taxonomy for the group. Continuity with the literature would be disrupted if Melanosuchus were converted as the species name, because the status of M. fisheri would be uncertain.