Hello,
 thank you for the many friendly mails. I already answered most questions
privately. Sorry, I cannot summarize questions to the Classification so
shortly. I think I can afford to relay  my „Comments upon the 5. edition to
my book"  that I have written for a German magazine. I hope, the essential
questions are answered with it.
Sincerely,
Gert
[log in to unmask]


Comments upon the 5. rewritten and extended edition 1999

„Pantha rhei, ouden menei“ (everything is flowing, nothing remains). – this
idea of the eternally change of all things, once thought out by HERAKLIT
(fifth century b.c.) – may serve as an explanation why this manuscript for
this fifth edition had to be totally rewritten.

You will not find another biological field where the discussion on taxonomic
principles has led to so comprehensive changes in such a short time as in
malacology. Almost all well known authors have been involved into this
discussion. The changing discussions concerning the validity and usefulness
of old and new taxonomic terms caused big uncertainty and helplessness – at
least at the interested people who were dependant on a consensual concept
and who should not be scold for still using antiquated taxonomic terms due
to the actual confusion concerning the taxonomic decisions. An accepted
reference system requires stability and continuity – only the old system
seemed to comply with these requirements, despite of its many changes and
updates.

The first classifications on gastropods oriented on the shape of the shell
only. Later new groups were brought in, e.g. on the basis of the gill
structure (Prosobranchia – Opisthobranchia), the heart (Monotocardia –
Diotocardia), the nervous system (Streptoneura – Euthyneura), the radula
etc. The largest attention has been payed to the classification of
gastropods by J. Thiele, published in 1929-1931. In this work Thiele
integrated the older classifications – mainly based on organs, but he also
regarded the radula, breathing and nervous system. Three sub classes have
been formed (Prosobranchia, Opisthobranchia, Pulmonata), and Pulmonata has
been split into three orders – Archaeogastropoda, Mesogastropoda,
Neogastropoda. Thiele regarded each order as a representation of a higher
stage of development.

The classification published by Thiele has been accepted, used and modified
by almost all malacologists including the authors of the big systematic
handbooks (WENZ 1938, HYMAN 1967, BOSS 1982). But this way also the negative
aspects of this system became visible. Already the unification of
Opisthobranchia and Pulmonata into one group Euthyneura (BOETTGER 1954,
ZILCH 1959-1960, TAYLOR & SOHL 1962, SALVINI-PLAWEN 1990) did not found
general acceptance. Examinations of some small, puzzling gastropods revealed
anatomic peculiarities that could not be explained by limitations due to the
small size. Large taxonomic groups like the superfamily Rissooidea,
containing lots of small gastropods, showed more and more heterogenous
character. So regarding the Pyramidelles, for a long time classified as
Mesogastropods, many more similarities with Opisthobranchia have been found.
The japanese malacologist S. KOSUGE (1966) examined the family Triphoridae
and detected that they did not belong to neither the Prosobranchia nor the
Opisthobranchia. He put them – together with some other quite different
families (Architectonicidae, Mathildidae, Epitoniidae, Janthinidae) – into a
new subordo Heterogastropoda. W.F. PONDER (1973) called the classification
by Thiele in question when he examined the relations of the Neogastropods,
coming to the result that this group could not have been derived from the
highly developed Mesogastropods. Because of the original characteristic of
Patellogastropoda (Diotocardia) – previously assigned to Archaeogastropoda -
a new subclass (Eogastropoda) had to be defined.

The actual classification is structured according to the historical
development. Paraphyletic terms like Prosobranchia, Heterostropha,
Opisthobranchia, Pulmonata are rejected today, but many authors still use
them due to practical reasons. These terms - without any classificational
value - are still useful for orientation, so in the book they are mentioned
in brackets, following the extensive work “Mollusca – The Southern
Synthesis, Fauna of Australia, Vol. 5”, 1998, two volumes containing 1234
pages, up to 70 authors have been involved in this work. The biggest part of
the Archaeogastropoda has been assigned to the superordo Vetigastropoda.
Most of the groups of Mesogastropoda have been assigned to the superordo
Caenogastropoda. Other paraphyletic terms (Streptoneura, Allogastropoda) are
only occasionaly found in literature yet and only as synonyms.

The discussion concerning the classification did not come to an end, of
course, the more so as the character of the underlying phylogenetic
schematic is mostly hypothetic and the investigation is still ongoing. But
the global direction seems to be commonly accepted.

Because the book has been completely rewritten, it was possible to integrate
the micromolluscs that have not been mentioned in the previous four editions
and that shell collectors are more and more interested in. The number of
mentioned families has been increased by 100 and reached now the sum of 316,
so all actually known families of shell bearing marine molluscs should be
registered in this edition.

In order to preserve the necessary overview for the user, the book does not
show the systematic structure of phylogenetic-cladistic based groups. So,
superfamilies, families and genus are listed in alphabetic order behind the
typus group of the superior taxon.

Nomenclaturical data (the author and the year) of higher taxa (above species
and genus) are rarely found in most works and – if the original literature
is not accessible – it may be very hard for the user to determine these
data. Many people will not set a high value on these data and just for
structuring a collection these data will be dispensible. Other users who are
looking for orientation concerning the taxonomy, these data will be
important and it will be interesting to get additional information on
correlations and original works.

So some time ago many people living all over the world were involved into a
discussion in the internet (Conch/L) about the question who (and when)
introduced “Mollusca” firstly into the nomenclature. It took quite a long
time until they found out that CUVIER assigned Mollusca firstly in 1795. The
correct description “Mollusca CUVIER 1795” in the literature would have
shown easily that Mollusca has originally been described in «Mémoire sur la
structure interne et externe, et sur les affinités des animaux auxquels on a
donné le nom de Vers; lu à la société d’Histoire-Naturelle, le 21 floréal de
l’an 3. – La Décade philosophique, littéraire et politique, 5 (3): 385-396,
Paris », dated 30.5.1795 – and in addition it would show the connection to
the french revolution that brought up a new chronology : “floréal” has been
the eighth and “prairial” has been the nineth month of the french revolution
calendar in the year “3” of the first french republic = 1795. In these times
french malacologists had to shorten their names in order to hide their
aristocratic origin as LAMARCK (correct name JEAN-BAPTISTE PIERRE ANTOINE DE
MONET, CHEVALIER DE LA MARCK) or they had to flee to other countries as
BRUGUIÈRE (1792) who had to stop for this reason his big work on
“Encyclopédie Méthodique”, just arrived at the letter “C”.

All right! The actual terminology will surely contain lots of names that
will look strange to users who used the older classification in the past.
For these people the addional data may be helpful for orientation – the
description “Eogastropoda PONDER&LINDBERG 1996” will show clearly that this
term is not part of the classification used before 1996. Author and year
give a hint concerning the original literature – just imagine, this
information would be missing here.

Due to the many new terms included into this edition, the number of pages
has been increased by 63. The layout contains now two columns and optimizes
readibility this way. Also the type of binding has been optimized, so the
problem of loose pages will belong to the past.

Literature list
BEESLEY, P. L., ROSS, G., J. B. & WELLS, A. [edit.] (1998): Mollusca: The
Southern Synthesis. Fauna of Australia Vol. 5. – Teil A: xvi 563 S., Teil B:
viii S. 565-1234. Melbourne (CSIRO Publishing).
BOETTGER, C. R. (1954): Die Systematik der euthyneuren Schnecken. – Verh.
dtsch. zool. Ges: 253-280 (Zool. Anz. Suppl. 18: 253-280).Tübingen.
BOSS, K. J. (1982): Mollusca. – In: PARKER S. P. [edit.]: Synopsis and
Classification of Living Organisms Vol. 1. – S. 945-1166. New York
(McGraw-Hill Book Company).
BRUGUIERE, J. G. (1789-1792): Encyclopédie méthodique ou par ordre de
matières. Histoire naturelle des Vers, des Mollusques .... – Vol. 1: 1-758.
Paris.
CUVIER, G. L. (1795): Mémoire sur la structure interne et externe, et sur
les affinités des animaux auxquels on a donné le nom de Vers; lu à la
société d'Histoire-Naturelle, le 21 floréal de l'an 3. – La Décade
philosophique, littéraire et politique 5 (3): 385-396. Paris.
HYMANN, L. H. (1967): The Invertebrates, Volume VI, Mollusca I. – vii 792 S.
New York (McGraw-Hill Book Company).
KOSUGE , S. (1966): The family Triphoridae and its systematic position. –
Malacologia 4 (2): 297-324. Ann Arbor, Michigan.
PONDER, W. F. (1973): The origin and evolution of the Neogastropoda. –
Malacologia 12 (2): 295-338. Ann Arbor, Michigan.
PONDER, W.F. & LINDBERG, D.R. (1996): Gastropod Phylogeny - Challenges for
the 90s. – In TAYLOR, J. D. [edit.]: Origin and Evolutionary Radiation of
the Mollusca. – S. 135-154. Oxford (The Malacological Society of London,
Oxford University Press).
SALVINI-PLAVEN, L. von (1990): Origin, Phylogeny and Classification of the
Phylum Mollusca. – Iberus 9 (1-2): 1 – 33. Barcelona
TAYLOR D. W. & SOHL N. F. (1962): An Outline of Gastropod Classification. –
Malacologia 1 (1): 7-32. Ann Arbor, Michigan.
THIELE, J. (1929-1931): Handbuch der systematischen Weichtierkunde, Band
1. – 778 S. Jena.
WENZ, W. (1938): Gastropoda, Teil 1: Allgemeiner Teil und Prosobranchia. –
In SCHINDEWOLF, [edit.]: Handbuch der Paläozoologie, Band 6. – 1639 S.
Berlin (Verlag Gebrüder Bornträger).
WENZ, W. (†) cont. by ZILCH, A. (1959-1960): Gastropoda, Teil 2:
Euthyneura. – In SCHINDEWOLF, O. H. [edit.]: Handbuch der Paläozoologie,
Band 6. – 834 S. Berlin (Verlag Gebrüder Bornträger).