CactiGuide.com

What reference is google using for plant synonimity? It's terrible. It must be a very outdated reference.
For example search parodia erubescens and you'll get echinocactus erubescens, gymnocalycium bruchii is frailea bruchii and so on...

ElieEstephane wrote: ↑Wed Jan 17, 2018 9:02 am For example search parodia erubescens and you'll get echinocactus erubescens

I don't think that is very odd. Seventy years ago almost all global cacti were grouped within the genus Echinocactus.

It depends whether they were quoting the basionym the plant was originally published as since all later names are permanently attached to this basionym, which is the first quoted under it's present accepted name in a proper synonymy? The length of a synonymy can depend on how much of a "Lumper" the author is, or how many times the same species has been renamed in ignorance of previous publications.

As you can see from the synonymy's below Parodia erubescens was originally published as an Echinocactus by Van Osten and Gymnocalycium bruchii as a Frailea by Spegazzini, those are the basionyms of those species. If later combinations are made the author of the basionym is always quoted in brackets, with the author making the new combination following, as with P. erubescens (Osten) D.R.Hunt.

Synonymy:-

Parodia erubescens (Osten) D.R.Hunt
Echinocactus erubescens Osten
Notocactus erubescens (Osten) Marchesi
Ritterocactus erubescens (Osten) Doweld

Synonymy:-

Gymnocalycium bruchii (Speg.) Hosseus
Frailea bruchi Speg.
Astrophytum bruchii (Speg.) Halda & Malina
Gymnocalycium bruchii f. albispinum (Backeb.) W.Till
Gymnocalycium albispinum Backeb.
Gymnocalycium lafaldense f. albispinum (Backeb.) Oehme
Gymnocalycium bruchii subs. atroviride Neuhuber
Gymnocalycium bruchii var. brigittae Piltz
Gymnocalycium bruchii subs. matznetteri var. briggitae
Gymnocalycium bruchii var. matznetteri f. brigittae (Piltz) Neuhuber
Gymnocalycium bruchii var. centrispina hort.
Gymnocalycium bruchii f. cristata Hosseus
Gymnocalycium bruchii subs. cumbresitense Neuhuber
Gymnocalycium bruchii var. deviatum (Oehme) U.Becker
Gymnocalycium lafaldense f. deviatum Oehme
Gymnocalycium bruchii subs. elegans Neuhuber
Gymnocalycium bruchii var. enorme (Oehme) Backeb.
Gymnocalycium lafaldense f. enorme Oehme
Gymnocalycium bruchii var. evolvens (Oehme) U.Becker
Gymnocalycium bruchii var. glaucum Neuhuber
Gymnocalycium bruchii var. hossei Backeb.
Gymnocalycium lafaldense f. hossei (Backeb.) Oehme
Gymnocalycium bruchii subs. implexum Neuhuber
Gymnocalycium bruchii subs. lacumbrense Neuhuber
Gymnocalycium bruchii subs. lafaldense (Vaupel) Neuhuber
Echinocactus lafaldensis (Vaupel) A.Berger
Gymnocalycium bruchii var. spinossimum (Haage jr.) Y.Itô
Gymnocalycium lafaldense Vaupel
Gymnocalycium lafaldense f. spinossimum Haage jr.
Gymnocalycium bruchii subs. matznetteri (Rausch) Neuhuber
Gymnocalycium andreae var. matznetteri Rausch
Gymnocalycium matznetteri hort.
Gymnocalycium bruchii subs. melojeri Neuhuber
Gymnocalycium bruchii subs. melojeri var. rubroalabastrum Neuhuber
Gymnocalycium bruchii var. rubroalabastrum Neuhuber
Gymnocalycium bruchii subs. multicostatum Neuhuber
Gymnocalycium bruchii var. niveum Rausch
Gymnocalycium bruchii var. niveum f. cristatum hort.
Gymnocalycium bruchii subs. pawlovskyi Neuhuber
Gymnocalycium bruchii f. proliferum hort.
Gymnocalycium bruchii subs. renatae Neuhuber
Gymnocalycium bruchii subs. shimadae Neuhuber
Gymnocalycium bruchii var. spinosior hort.
Gymnocalycium bruchii subs. susannae Neuhuber
Gymnocalycium bruchii f. svecianum (Pazout ex H.Till) Neuhuber
Gymnocalycium andreae var. svecianum Pazout
Gymnocalycium andreae f. svecianum Pazout ex H.Till
Gymnocalycium bruchii subs. matznetteri f. svecianum (Pazout ex H.Till) Neuhuber
Gymnocalycium lafaldense var. evolvens Oehme
Gymnocalycium lafaldense f. fraternum Oehme

I see now. I knew they were basionyms but i think it's a little misleading

I doubt it's using any formal synonymy. Like everything else, it'll provide pages based on words or phrases that are often found together in webpages or that an algorithm deems to be similar or equivalent - however it manages to do that! It's pure luck if these are formal synonyms.

Just don't rely on google synonymity but on your own knowledge. Most of the pictures on 2nd search page of the net engines are already wrong.

I don't think that is very odd. Seventy years ago almost all global cacti were grouped within the genus Echinocactus.

Well, there was also some Opuntia, Cereus & Mammillaria, wasn't it?