i actually think to the untrained eyes the palmas palmas and palmas buettikoferi would be hard to tell apart as they have the same body shape, same dorsal finlets number (7-9 typically). the biggest difference is their patterns. imo palmas palmas is the prettiest bichir around.
palmas polli is actually very different compared to the other two and is easy to distinguish. its markings are different (again mine isn't a good example since you can't see its markings that well). typically 5-7 dorsal finlets. its body shape is different from the other two, especially as it grows, as it tends to get fat. its head is more pointed as well.
palmas polli is very often mislabeled as 'retropinnis' at lfs. sometimes they'll just be called 'palmas'. chances are this is the subspecies seen at lfs as its by far the most common of the three subspecies.
palmas palmas is pricier since its rarer (rarest of the three), and it showed up later in the hobby, only recently does the supply become more steady.
palmas palmas and palmas buettikoferi pretty much have the same sorta behavior. both aren't really the active type, and both do enjoy their hiding spots. On the other hand, palmas polli is by far one of the most active bichir, along with senegalus.
in short, to tell p.palmas and p.buettikoferi apart, you need to rely mostly on body markings. to tell p.polli from the other two, use patterns, color, dorsal finlets, overall look.
any more questions, feel free to ask
