Thanks for that, Harry. Those characters together make a strong case
for separation.

>  The NZ species has a long fossil record and several synonyms
> according to the authors.

Yes, it arose by the early middle Eocene (local Bortonian stage, which
coincidentally is largely correlative to the Bartonian!), so it goes
back about 40my. Of course if we had the fossil animals to study we'd
probably decide that it was a continuous lineage of several species,
but on shell characters alone, which is all we will ever have, it has
to be regarded as a single species.


--
Regards
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
Mollusc, Toyota & VW van fan

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