Thank you for your clear explanation!
Sylvia
Van: Conchologists List [mailto:[log in to unmask]] Namens Pearce,
Timothy
Verzonden: woensdag 20 maart 2024 00:20
Aan: [log in to unmask]
Onderwerp: Re: [CONCH-L] Help with Taxonomic Order of Families
Regarding alphabetical order or not, many classifications try to reflect
history of life. While there *IS* a true history of life (parents have
children, ancestors beget descendents) we don't KNOW that truth, so we make
our best guess. With new information, we modify our guesse sand
classifications change (it's not just to annoy you).
When an ancestor gives rise to two lineages, many criteria could justify
which lineage to list first. A convention many classification schemes use
now is alphabetical order. But it's just a convention. Your reason to use
another order should be fine.
However, be sure to reflect nested hierarchy. If ancestor A gave rise to
descendent lineages B and C, and then B gave rise to D and E, then D and E
could be listed in any order, but don't put C BETWEEN D and E (if you want
to depict ancestor-descendent relationships) because C is from a different
lineage.
D
B <
/ E
A <
\
C
For your taxa of interest, I checked Molluscabase for names of higher
categories. Our current best guess is that the first Gastropoda (listed as a
class) gave rise to several lineages; the TWO relevant here are
Caenogastropoda and Heterobranchia (as subclasses); Caenogastropoda gave
rise to several, the ONE relevant is Littorinimorpha (as order) and
Littorinimorpha gave rise to several, the TWO relevant are Rissooidea and
Vermetoidea (as superfamilies), with Zebinidae in Rissooidea and Vermetidae
in Vermitoidea. Heterobranchia gave rise to several lineages, the ONE
relevant is Tectipleura (as subterclass), which gave rise to several
lineages, the TWO relevant are Aplysiida and Ellobiida (as orders), with
Aplysiidae in Aplysiida and Ellobiidae in Ellobiida. I left out some
intervening categories, so don't worry if you don't see a particular
taxonomic category listed.
Rissooidea ---
Zebinidae
/
Caenogastropoda --- Littorinimorpha
/ \
/ Vermetoidea ---
Vermetidae
/
Gastropod Aplysiida --- Aplysiidae
\ /
Heterobranchia --- Tectipleura
\
Ellobiida --- Ellobiidae
To reflect ancestor-descendent relationships, you can list Zebinidae and
Vermetidae in any order, but they should be together and not mixed with
Aplysiidae and Ellobiidae, which two can also be in any order but not mixed
with Zebinidae and Vermetidae. I think the following 8 arrangements are the
only ones that preserve the ancestor-descendent relationships (A=Aplysiidae,
etc.):
(1) A, E, V, Z; (2) A, E, Z, V; (3) E, A, V, Z; (4) E, A, Z, V; (5) V, Z, A,
E; (6) V, Z, E, A; (7) Z, V, A, E; (8) Z, V, E, A. Any of those orders
should be acceptable. Choose the one most convenient for you.
Best wishes, -Tim-
Timothy A. Pearce, Ph.D., Assistant Curator, Section of Mollusks
Carnegie Museum of Natural History
4400 Forbes Ave, Pittsburgh, PA 15213-4080, USA
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