I’ve seen many many artists, including myself, being able to draw “okay” hands - but the thumb always ends up weird like this:
In many MANY examples of hands, the thumb is drawn like it was this big lump of “something” lacking one or any joints at all.
Hands in general, are more or less a big bunch of joints, so if you don’t keep that in mind when drawing, you might end up with weird fingers. SO PAY ATTENTION TO THE GODDANG JOINTS OKAY?!
NOW THIS IS HOW IT SHOULD LOOK LIKE:
(to get the book as pdf: JUST GOOGLE “BRIDGMAN CONSTRUCTIVE ANATOMY” and you’ll find the website with the download link)
In order to easier draw the thumb (and the rest of the hand as well) is to exaggerate the shapes and features. That is the “key” to understand how anatomy can vary so much but still follow the same basic construction:
Aaaaand here’s some more examples of DELICIOUS THUMBS:
NOW GO AND DRAW THUMBS!
DISCLAIMER: Baby-hands and hands on more overweight people tend to not be as “bony” as in my examples shown here. But they are still divided in the same pattern, but slightly rounder.