Dear Jen: Thumbs up from me.
Dear Matt: excellent comments!
   Thanks and 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
ph 412-622-1916; fax 412-622-8837; [log in to unmask]
https://carnegiemnh.org/research/mollusks-malacology/
Snails & Slugs of NE USA: https://carnegiemnh.org/mollusks/land-snails-slugs/
I tell snail jokes: www.tiktok.com/@carnegiemnh; www.instagram.com/carnegiemnh/
Snail Jokes 2020 compilation (14 min) https://www.youtube.com/watch?v=v9hByyJBIws

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Topics of the day:

  1. Help with Taxonomic Order of Families

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Date:    Wed, 20 Mar 2024 09:58:17 +0100
From:    Sylvia op facebook <[log in to unmask]>
Subject: Re: Help with Taxonomic Order of Families

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 ph 412-622-1916; fax 412-622-8837;  <mailto:[log in to unmask]> [log in to unmask]  <https://carnegiemnh.org/research/mollusks-malacology/>
https://carnegiemnh.org/research/mollusks-malacology/

Snails & Slugs of NE USA:
<https://carnegiemnh.org/mollusks/land-snails-slugs/>
https://carnegiemnh.org/mollusks/land-snails-slugs/

I tell snail jokes:  <http://www.tiktok.com/@carnegiemnh>
www.tiktok.com/@carnegiemnh;  <http://www.instagram.com/carnegiemnh/>
www.instagram.com/carnegiemnh/

Snail Jokes 2020 compilation (14 min)
<https://www.youtube.com/watch?v=v9hByyJBIws>
https://www.youtube.com/watch?v=v9hByyJBIws




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