Duplicate Genus names?

I thought that the rules of nomenclature prevented the same genus name being used for different classes of organisms. The genus Monarcha in the Class Aves, as well as in the Order Lepidoptera, would seem to violate that…


I think there was a genus of fungi that shared a name with a plant, too. Forget which, but I’ve seen it happen.
I used to think it was one per kingdom, but perhaps there are exceptions?

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It is actually surprisingly common, this database documents over a thousand examples:

Also here :


I think it is unusual that the genus Monarcha would be allowed to be used twice within the same Kingdom, even though the two genera are in different classes. Insects and vertebrates are both covered under the same nomenclatural code (ICZN).

I think this is one that will be resolved at some point. The source I can find for the name is from 1999, and the bird genus dates to 1827. One source I looked at since points out that the name is already in use, and the other uses “Monarcha”, indicating at the very least some uncertainty over the validity.

I always get bothered by Knowltonia, a rare Buprestid genus and some genus of plant called Burnleafs. It makes it hard to ID Knowltonia (Buprestid) genus, since there are way more plants in the genus than insects in their genus.

Yes those plants are ours. Shade loving, beautiful leaves and understated flowers.

@allen4 different kingdoms(?) of organisms have different nomenclature, so you can name a plant and worm the same name. Insects and vertebrats seem to be divided too.

Organisms from different kingdoms can have the same names (see for instance the three genera named Gordonia), and in some cases, groups within the same kingdom but different ranks. I’m not sure how it is for plants, but the ICZN, which governs animal names, is largely unconcerned with ranks above family, so valid homonyms in the same kingdom can arise: the name ‘Apoda’ is a valid both as a genus of moths, and a subgroup of amphibians, but any other animal genus (or subgenus) called Apoda would be invalid as a junior homonym of the moth, and would have to be renamed. In the case of Monarcha, the bird genus appears to have priority, and the single moth species in “Monarcha” is in the process of being reclassified per Strutzenberger 2018 and Brehm et al. 2019. Previously unrecognized invalid homonyms in the same kingdom are still found occasionally, aided by the proliferation of digitized books and Internet databases, so it’s easier to discover that say, a genus name given to a nematode found in tropical butterflies was already given to a fossil clam 150 years ago.


Plant names and animal names are governed by different rules – the International Code of Nomenclature for Algae, Fungi, and Plants and the International Commission on Zoological Nomenclature for animals. There is also an International Code of Nomenclature of Prokaryotes.

Within each code, there cannot be duplicate names, but there are some genera that have the same name in, say, plants and animals at the same time, as others have mentioned.

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Thanks for all the very interesting replies. It seems there is a lot to clean up in order to be consistent with ICZN. One other that I remember from years ago that may or may not still be valid is the genus Platycercus that is assigned to a group of Australian parakeets, as well as some Stag Beetles…

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Looks like Platycerus is the beetle, while Platycercus is the parakeet, so they’re similar but not identical (perhaps one was changed in the past?). Other “okay” animal homonyms involving suprafamilial names include Siphonophora (an alternate but still used name for the cnidarian order Siphonophorae), and Siphonophora, a genus of millipedes.

Usually when two or more taxa are found to have the same genus name or genus+species combination, the oldest name is kept, but in some rare cases the more recent name is kept, upon special petition to the International Commission of Zoological Nomenclature (e.g. if the newer name is much more widely used, and/or the older name improperly assigned, and/or if changing the new name would wreak havoc on the taxonomy of well-established tribes, subfamilies, and family names based on the name).

Coincidentally (and totally unrelated to the cnidarian name) the millipede genus Siphonophora mentioned above (described in 1837, and the namesake of the family Siphonophoridae and order Siphonophorida) was kept upon petition to the ICZN despite the name being previously given to a bryozoan in 1823 (you can read about it here). And lastly, just to make things more confusing, an aphid genus was also named Siphonophora in 1855, but this is invalid due to the earlier millipede name. Phew!


There are names referred to as parahomonyms which are described genera that are disallowed under the zoology and botanical codes because they are too similar in spelling to an earlier valid genus name, which could cause confusion. I don’t think that would apply in this case because -cerus and -cercus are (I believe) derived from different roots with different meanings.


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