A fact from Metridium senile appeared on Wikipedia's Main Page in the Did you know column on 13 September 2011 (check views). The text of the entry was as follows:
Metridium senile is within the scope of WikiProject Animals, an attempt to better organize information in articles related to animals and zoology. For more information, visit the project page.AnimalsWikipedia:WikiProject AnimalsTemplate:WikiProject Animalsanimal articles
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"This anemone is perhaps better known by its synonym, Metridium senile, a name now considered invalid."
You are correct, WoRMS (ref 1 in the article), lists the subspecies Metridium dianthus sindonea Gosse as now accepted as Metridium senile (Linnaeus, 1761) - a separate species. I will amend the syn list to reflect this. Loopy30 (talk) 13:33, 1 August 2018 (UTC)[reply]
(edit conflict) When I created the article in 2011, the accepted name was Metridium senile and that was what the article was called. Then in 2017, in response to a request by Rhinopias (talk·contribs), user Alex Shih (talk·contribs) moved the article to Metridium dianthus. I expect this was as a result of changes in taxonomy on WoRMS, which now seems to have been revised yet again. You can see the different versions if you click on the "History" tag on the article page, and each revision of the article is available by clicking on its link in the list. It is difficult for Wikipedia to keep up with changes in taxonomy but user Loopy30 is doing his best. Cwmhiraeth (talk) 13:40, 1 August 2018 (UTC)[reply]
While I cannot see older versions of the WoRMS page (Internet Archive, Wayback machine?) to see the older taxonomy, I have reviewed the article history and the move request by Rhinopias (talk·contribs) here on Wikipedia. As minimal changes have been done to the article since its move, I recommend that it be moved back to its original name and a new stub created at Metridium dianthus. 'Cheers, Loopy30 (talk) 13:56, 1 August 2018 (UTC)[reply]