As has been noted, almost all details of classification have been questioned by
at least one author.  Another difficulty is the issue of cladistic
classification versus traditional nomenclature.  Despite the efforts of some
cladists to throw out the Linnaean system in favor of some cladistic approach,
the best way to express cladistic classification is with a diagram.  The
Linnaean system provides a good way to unambiguously identify taxa and give a
general idea of its characteristics and relationships.

For the Bivalvia, most recent classifications are strongly influenced by the
Treatise on Invertebrate Paleontology, which in turn drew largely on papers by
Cox and Newell.  However, very different classifications have been put forward
by Starobogatov and Scarlato.  The most recent version of this of which I am
aware is Starobogatov, 1992, in Ruthenica.  The Cryptodonta of the Treatise has
largely been abandoned, with most workers putting the solemyoids with the
paleotaxodonts and the remainder as pteriomorphians, but recently Paul Johnston
and co-authors have advocated recognizing the non-solemyoid cryptodonts, along
with some traditionally pteriomorph groups, as a distinctive Cryptodonta.  I
would group them as a distinctive subgroup within Pteriomorphia.  These
cryptodonts are all extinct.

The Southern Synthesis has a somewhat mixed classification for the Gastropoda,
as it acknowledges.  The project was started and organized before major
revisions came into prominence, so you need to read carefully to decide what is
what rather than simply copying the table of contents.

For the Bivalvia, a variety of modifications in classification have been
proposed which seem well-founded.  Some of the relevant papers postdate the
Southern Synthesis; others are relatively obscure; and some unpublished data
from last year's meetings and my rsearch also affect the comments.  As the
original post noted, taxa not known from Australia  are not always mentioned,
though some do receive at least brief coverage either as being of particular
interest or likely to be found at a later time.

The phylogenetic diagram on p. 5 is very peculiar for the Bivalvia, both in the
suggested times of origin and in the relationships.

For the general section on Bivalvia, a couple of notes on the fossil history
section:
Fordilla is Early Cambrian, not Middle or Upper.  Pojetia has been recently
reported from the Middle Cambrian.  An Early Ordovician pterineid has been
reported recently from Wales (Cope, 1996).

For Protobranchia, the systematic placement of several proposed families
remains debated, primarily for the rarely-collected deep sea taxa.

For Pteriomorphia, unpublished DNA work and morphological cladistic studies
will lead to some rearrangements of Limoida, Plicatuloidea, Anomioidea and
Pectinoidea.  Published DNA studies, as well as some previous morphological
work going back at least to Jackson, 1890 and unpublished DNA work, groups
Ostreoidea with Pterioida rather than with Pectinoida.  The  exact placement of
arcoid families is also uncertain, with some probably paraphyletic or
polyphyletic.  The families in Pterioidea may also need revision.

For Paleoheterodonta, Hyriidae should be with Muteloidea rather than
Unionoidea.  The proper name for Muteloidea is not entirely clear, as different
references cite different dates and authors for family-level names, and I have
not been able to track down the original references from the first half of the
1800's.  Etheridae is polyphyletic.

For Heterodonta, DNA data suggests some rearrangements, but much is based only
on preliminary data and needs confirmation.  Better-documented changes include:
Neoleptonidae and probably Cyamiidae are close relatives of Veneridae, whereas
Sportellidae is close to Galeommatidae.  Exact classification is still
unsettled.  Further morphological and DNA work supports demoting Tridacnoidea
to Tridacninae within Cardiidae.  The text notes some of this work.  Trapezidae
has only one i due to an ICZN decision to avoid the homonym with an arthropod,
if I recall correctly what Trapeziidae is.  Park and O Foighil recently (2000)
published DNA work suggesting that Corbiculidae and Sphaeriidae are not closely
related, for which there is some morphological evidence, but more work is
needed.  Myoida is polyphyletic, based on DNA and morphological work.

Anomalodesmata is still poorly represented by DNA data (four unpublished
samples, two doubtful short sequences, and one unpublished contaminated
sample), so little new can be added.

Dr. David Campbell
[log in to unmask]