There are three palmas subspecies, the one that's most common and most likely to show up at LFS is palmas polli.
This pic below from the link above is a very good representation of what a palmas polli looks like (except small ones at LFS wouldn't be as fat/round). Other than color and pattern differences from a senegalus, the number of dorsal finlets is different too, around 8-9 usually for senegalus, and 5-6 for polli.