I have found the following species all having knobthorn as all or part of one or more of their common names and I have no idea which of them are represented on this page except as stated with specific pieces.
planks listed as African knobthorn --- I assume the first side shown is planed and the second is with a patina
plank and closeup from a vendor whose pictures are generally purple, regardless of what color the wood actually is, so I have zero faith in the purple color shown here.
plank and closeup from the same vendor as those directly above
pen blanks that have been oiled and waxed --- these are from a pen blank vendor who makes most of her wood look purple regardless of what the wood actually looks like, so I have zero faith in the purple color shown here.