Sorry but this doesn't look like B. Erythrophylla which has shiny rounded kidney shaped leaves and a red underside.
https://stevesleaves.com/produ...
https://www.taylorgreenhouses....
https://littleprinceplants.com...

Thank you for your note. This plant does make round leaves, and also the more star-shaped leaves in that particular pic. The reverse is red:


https://www.begonias.org/rhizo...

The red fits, the star shaped doesn't.

The conditions really affect the leaf shape.

It looks like the plant @ the ABS link, and the links you shared:
https://www.begonias.org/rhizo...

And these:

https://www.duchyofcornwallnur...
http://www.botanic-gardens-lju...
https://national-begonia-socie...
https://www.nparks.gov.sg/flor...
https://sfbegonia.org/past-eve... (Tom's collection)
https://sucsforyou.com/2020/04...
https://www.benaranurseries.co...
https://davesgarden.com/guides...
https://www.buxtonbegonia.org/...
https://littleprinceplants.com...
http://begoniacollection.ru/en...
https://www.candy.com.sg/29-be...
https://waterandlight.nyc/prod...

Tiffany, I'm not here to argue with you but I am very confused. Every single link I provided and the additional ones you linked clearly show the rounded kidney shaped leaves on the species as well as some of the cultivars from that species you linked. I do not see that resemblance on any of the leaves of your image, most, if not all, are notched & have an almost maple shaped leaf. Loretta's image could be a sport/cultivar derived from the species or even be mislabeled. I've often seen that in plant shows.

This is text from the link Tiffany gave to the American Begonia Society page:

"B. 'Erythrophylla' is an early hybrid that is often called the beef steak Begonia because of its large, kidney-shaped leaves. Rhizomatous leaves have intricate patterns and almost any earth tone color. Some are hairy-leaved, some are round and shiny, and others are star-shaped. There is really no end to the variety of leaf shape, color and texture in this type of Begonia."

Sheesh, missed that, sorry Tiffany! (Thank Lin!)
No wonder there is a lot of confusion with begonias! How is anyone supposed to properly ID a plant with such an all encompassing description?!!

I was not arguing, just investigating. My plant has made round leaves at times, and leaves with points at times, looking exactly like so many pics. There are some cultivars of erythrophylla, but it seemed better to put pics @ the species level vs. guessing @ one of the cultivars.

In the Steve's leaves pic, one leaf in the front has a definite point on it. The pics @ Little Prince also show leaves with some points.

That's a good question! ; )

I wasn't questioning the points which do seem more common and I have seen several, I was questioning the maple shape with the notches all around.

I've wondered about that too, why the leaves are sometimes almost perfectly round and sometimes have a much more mature shape, for lack of a better descriptive word.

Check out "Beefsteak & Rumba" pic from this post. You can't find 2 leaves with the exact same shape, all coming from a single rhizome:
https://garden.org/thread/view...

It seems like I've asked if other people's Begonia is so schizo but I can't find that discussion.

Schizo is a good word!

It is a strange plant, sometimes making white blooms & sometimes pink. That seems to be a result of less vs. more light, but I can't detect the pattern of variables in regard to the leaf shape. I wonder if high humidity is a factor since that's something I can't control and almost always have in abundance, even inside because our heat, when needed sporadically, doesn't dry the air.