>Not sure what you mean by "valid,"

I meant available names.

>but the phenomenon of cryptic species is real: taxa that have
>speciated without readily visible features that track that
>speciation.  Evolution doesn't proceed for the convenience of
>systematists or nature aficionados.  Because the chief function of
>zoological nomenclature is to provide a vocabulary for talking about
>and understanding biological diversity, the "use [of] ... separating
>two species on such grounds" is to effectively communicate about
>that biological reality.

They may be real species, but only the individuals examined by
molecular (or possibly anatomical) techniques, or say observed to be
spawning at a certain time of year, can be identified. So for
practical purposes such cryptic species are indeterminable. This is a
quandary not easily decided either way. The names have to stand, but
the vast majority of specimens will not be able to be named to
species level.

Families such as Littorinidae, Hydrobiidae, Epitoniidae and
Pyramidellidae, which shells are often lacking in distinctive
characters, spring to mind.
--
Regards
Andrew

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