Taxacom: Collective groups and form(al) genera

Wed Jun 25 10:56:43 CDT 2025

Dear Francisco,

could you explain in a bit more detail what it means to not be able to 
"allocated with confidence to nominal genera". When dealing with 
fossils, especially those of arthropods, the story usually goes like 
this: Author A describes a species, the type specimens clearly do not 
belong to any previously described species. At this point, everything is 
still unproblematic. Then, other authors B and C add new fossils as new 
species to the same genus, usually without any proper reasoning and 
purely based on superficial resemblance and absence of differing 
features that are visible in the fossil. These authors usually not state 
that the genus will become a form genus or a collective group by 
including their new species. Only later, other authors D and E then call 
it a form genus. Does this genus name then qualify to be a collective 
group, even if the situation when the first species was described was 
unproblematic (monotypic genus)? My confusion probably relates to the 
term "nominal genus".

Thank you very much in advance!

Mario

On 6/25/25 17:12, Francisco Welter-Schultes via Taxacom wrote:
> Dear Ziv,
> If you propose a name for a collective group, that name would 
> automatically not have a type species no matter if you designate one 
> or not. You could not fix a type species for it, any type species 
> designation would be invalid. You could designate one, but only 
> ineffectively.
>
> For the collective group see the definition in the Glossary:
>
> "collective group. An assemblage of species, or stages of organisms 
> (e.g. eggs or larvae), that cannot be allocated with confidence to 
> nominal genera. Names proposed or used for collective groups are 
> treated as genus-group names but special provisions apply to them (see 
> Article 42.2.1)."
>
> If you propose a name for an assemblage of species which you cannot 
> allocate with confidence to nominal genera, you propose a name for a 
> collective group. Once this condition is met, "assemblage of species 
> which you cannot allocate", the rest follows automatically. As said 
> above, even if you designate a type species this act will be 
> ineffective and invalid. It would not render your name anything else 
> but a name for a collective group.
>
> If the form genera you are talking of were proposed for such 
> assemblages, which the authors demonstrably could not allocate with 
> confidence to nominal genera, they fall under the definition of a 
> collective group. Consequently these names do not have type species - 
> and any type species designation would be invalid.
>
> It is not possible to state "the form genera have type species, so 
> they are not collective groups". The condition of the Glossary 
> definition is superior. If they are collective groups because they 
> comply with the Glossary definition, they have no type species, and 
> any previously published type species designation is to be rejected as 
> invalid.
>
> This is how I understand the Code in this matter.
>
> I hope this helps.
>
> Best wishes
> Francisco
>
> Am 25.06.2025 um 04:50 schrieb Ziv Lieberman via Taxacom:
>> Hi all,
>> I'm thinking about the differences between "form" or "formal genera" and
>> "collective groups" and how to best approach these entities when
>> establishing new nomenclature.
>> In ants, there are many groups of fossil taxa which have been 
>> established
>> for convenience, without implying that they form a natural group - 
>> mostly,
>> e.g., impressions of wings or incompletely preserved fossils which 
>> can be
>> associated based on one or more morphological features. Authors 
>> generally
>> state that these are "form genera" (or, perhaps confusingly, "formal
>> genera", especially in the Russian school of paleontology). However, 
>> they
>> are nomenclaturally treated as "real" genera, including in that they 
>> have
>> type species.
>> To my understanding, these "form genera" align with the Code's 
>> definition
>> of collective groups: "An assemblage of species. . .that cannot be
>> allocated with confidence to nominal genera. Names proposed or used for
>> collective groups are treated as genus-group names but special 
>> provisions
>> apply to them". These provisions are given in 42.2.1 ("The names
>> established expressly for certain assemblages of taxonomic convenience
>> known as "collective" groups. . .established at the genus-group level 
>> are
>> to be treated as genus-group names in the meaning of the Code." 42.3.1
>> states "Collective groups have no type species."
>> Therefore, I arrive at the conclusion that even though many "form(al)
>> genera" are "established expressly for assemblages of taxonomic
>> convenience", they are *not* collective groups, since they have type
>> species.
>> This leads to my direct question: If I want to establish a new 
>> collective
>> group, should I follow 42.3.1 and not fix the name to a type species? 
>> This
>> seems like it must be the right answer, but I am hesitant because I have
>> never seen an example of such a name in practice.
>> Further, if the type species of a form genus is transferred to a 
>> type-free
>> collective group, are there any additional complications to consider?
>> Thank you!
>> -Ziv
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