Xus yus” : the problem of placeholder names in preprints

Xus wiki page

Screenshot of the “Xus yus” Wikipedia page as it appeared at the time of writing (latest edit dated June 22, 2021).

In a preprint posted to the bioRxiv server, Wendruff et al. (2018) described a new genus and species of cheloniellid arthropod from the Silurian Waukesha lagerstätte of Wisconsin. The International code of zoological nomenclature recommends that new names should be excluded from preliminary works like preprints and meeting abstracts (Recs. 8G & 9A; ICZN, 1999). The Code specifies that preprints and abstracts are not published works and any names within them are automatically unavailable (Arts. 9.9 & 9.10). Instead of withholding the name altogether, Wendruff et al. used the placeholder “Xus yus” for their new taxon. “Xus yus” originates from the Code itself, being used as a hypothetical example in Art. 70.3. Unfortunately, Wendruff et al. did not include a disclaimer that this was only a placeholder. They also stated the etymology for what was presumably [see addendum] the intended final name of this taxon, which does not match “Xus yus” (a meaningless assemblage of letters).

Xus etymology & code

The false etymology of “Xus yus” (top) and its original usage in the Code (bottom), modified from Wendruff et al. (2018) and ICZN (1999) respectively.

The preprint caused enough confusion that a Wikipedia page for “Xus yus” was created in 2019. It was clearly mistaken for a real name, as the page repeats the false etymology given by Wendruff et al. This is the perfect demonstration of why it is completely unnecessary to use placeholder names in preprints. The phrase “Cheloniellida gen. et sp. nov.” would have sufficed and obviously been a tentative designation. It would be much harder for those uninitiated in nomenclature (like some Wikipedia editors or the general public) to mistake this type of designation for an available name. Even using a placeholder, Wendruff et al. still could have limited confusion by including a disclaimer and leaving out the etymology of the final name. Authors of preprints describing new taxa really need to be more aware of the Code and nomenclatural practices.

Addendum (7/13/2021)

Wendruff (2016) contains the intended name for this taxon, “Latromirus tridens“, which has the same etymology as in the preprint. Note that this name is also not available since it was named in an unpublished dissertation (ICZN Art. 9.12).



2 thoughts on “Xus yus” : the problem of placeholder names in preprints

  1. Holy shit, the Wikipedia article is still up. I’ll try to do something about it immediately.

    Authors of preprints describing new taxa really need to be more aware of the Code and nomenclatural practices.

    No, they did nothing wrong: their placeholder name simply does not exist for ICZN purposes. The author of that Wikipedia article needs to learn the first thing about the ICZN and about languages – not even specifically Latin.


    1. The confusion could have been avoided if the authors of the preprint had used a designation like “Cheloniellida gen. et sp. nov.” instead of a placeholder that resembles a proper binomial. I agree that the author of the Wikipedia article should have realized that it was a placeholder, but the preprint authors are still partially to blame.


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