These genera have been incorporated into the genus Euphorbia:

The genus Pedilanthus has been submerged into the genus Euphorbia and is now known as Euphorbia pedilanthoides.

"Euphorbia is a highly diverse plant genus, comprising some 5,000 currently accepted taxa.[1]
The list includes the former (and never generally accepted) genus Chamaesyce, as well as the related genera Elaeophorbia, Endadenium, Monadenium, Synadenium and Pedilanthus which according to recent DNA sequence-based phylogenetic studies are all nested within Euphorbia[2]

Does this mean that I should update all plants and set the genus to Euphorbia and species to pedilanthoides where the genus is currently Pedilanthus?

I think you should!
I hate all these changes, but it does make sense in this case...

Many are already listed under the new genus (Euphorbia) but some are listed under the old genera as well so they are now appearing two places ... one correctly named and one not ... at least not anymore.

So we will have some duplicates then if I make the change wholesale.

There are only 6 plants in the Pedilanthus genus. That's a small enough number that they can be handled by just proposing the changes and proposing deletions when needed. Want to handle it?

And Monadenium and the others as well?

There is only one Monadenium in the database.

Anytime there are fewer than a dozen or so plants that need changing, it's actually faster to propose the changes one by one.

There are other species of those particular genera that are not listed in the ATP database. So, my question is, if someone comes along and adds a plant under the old genera, it will still be listed as that. Correct?

This is a general question for any situation like that.

Yes, I'll change the ones in there now.

Once we completely clear out a genus so that there are no plants left in that genus in the database, then from that point out nobody except me can add a plant with that genus back in.

dave said:Once we completely clear out a genus so that there are no plants left in that genus in the database, then from that point out nobody except me can add a plant with that genus back in.

Those are done and I think all the old listings are cleared out of of the old genera Pedilanthus and Monadenium.

I corrected the Synadenium (only one plant in the ATP database) and the remainder listed above had no listings ... except for Chamaesyce.

I thought I would just run over and take care of Chamaesyce quickly too but ... Is there an easier way than one-by-one??

There are 124 of those so I'll handle them with a script.

What needs to be done with Chamaesyce?

Chamaesyce is no longer a dedicated genus and is now in the genus Euphorbia. I'm beginning to sound like a broken record here.

Just wanted to confirm. I will update all plants with the genus Chamaesyce to be genus Euphorbia. Any species that are present will remain the same, right?

Confirmation is good. I just meant that everything seems to have gone to the genus Euphorbia.

Please let me double-check the Chamaesyce names before anything is changed. I've got the list around here somewhere. Some of the names may have changed. One thing is that some of the endings of the new names have changed to the feminine ending -a to match up with the feminine ending of Euphorbia.

I'm not a Botanist but think I can check the names. Maybe.

Apparently many recognize this as a subgenus of Euphorbia. What do you do in that case? Leave it as is in the database?

There's no harm in doing that. If some new information comes along we can always react at that time.

And much less confusing if someone is searching for it.