Dear Gary and others,

In his 1995 paper, Yuri draw another picture (leaving out many of the taxa
in the figure reproduced by Gary), which I will try to reproduce here

_ _
                             |-----------|----------------Oliva
  |
                             |           |
    | Olividae
                             |           |----------------Amalda      ___|
                             |
-----------------------------|----------------------------Olivella
  Olivellidae

(the figure is somewhat modified as Kantor also mentioned anatomical
changes that occurred along the lines, which are very hard to reproduce in
a good figure through this medium).
This figure made me make -I admit, a bit awkwardly phrased- the remark:
As far as I understand the figure by Kantor, Olividae are derived from
Olivellidae. Before they "became" Olivinae (subfamily), the subfamily
Ancillinae arose from the Olividae stock.
But maybe Gary can correct me in the interpretation of this figure.

Gijs


----------
> Van: Gary Rosenberg <[log in to unmask]>
> Aan: [log in to unmask]
> Onderwerp: Re: Olivellidae??
> Datum: donderdag 2 september 1999 23:05
>
> In answer to Art's question, there is no set amount or number of
> differences required to determine that something is a different species,
> genus or family. What is more important is the pattern of relationships.
In
> particular, the rules of phylogenetic classification demand that all taxa
> must be monophyletic. This means that all the descendants of a lineage
must
> be included within the taxon. In everyday terms, this means that the only
> things that you should name (above the species level) are the ones that
you
> remove from the tree with a single cut. Kantor's (1991) tree of
> relationships of oliviform gastropods, which I reproduce below, does not
> fulfill this requirement.
>
>        |---- Benthobia
> |------|
> |      |---- Pseudoliva (two species)
> |
> |------ Melapium
> |
> |              |-----Amalda dimidiata
> |         |----|
> |----*----|    |-----Amalda montrouzieri
>           |
>           |    |-----Oliva bulbosa
>           |----|
>                |     |----Olivella borealis
>                |-----|
>                      |----Olivella verreauxii
>
>
> Kantor places Olivella in Olivellidae and Amalda and Oliva in Olividae,
but
> Olividae is not monophyletic--to remove Olividae takes two cuts--one at
the
> asterisk, and one to remove the Olivellas. To be consistent, the
> classification should recognize either three subfamilies or three
families,
> Ancillidae/Ancillinae, Olividae/Olivinae and Olivellidae/Olivellinae.
Each
> of these can be removed with a single cut.
>
> I don't care whether they are ranked as subfamilies or families--that's
an
> arbitrary decision, and hence not a scientific one. However, I'd advocate
> retaining the traditional classification using subfamilies since it is
> consistent with the structure of the tree, whereas the classification
that
> Kantor proposed is not.
>
> >As far as I understand the figure by Kantor, Olividae are derived from
> >Olivellidae. Before they "became" Olivinae (subfamily), the subfamily
> >Ancillinae arose from the Olividae stock.
>
> Given that Kantor placed Amalda and Oliva in Olividae, his figure shows
> Olivellidae being derived from Olividae, not vice versa.
>
> Gary
>
> ---------------------------------------------------------------------
> Gary Rosenberg, Ph.D.                     [log in to unmask]
> Malacology & Invertebrate Paleontology    gopher://erato.acnatsci.org
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