"Cute" video, but:

I think, Mr. Milo that (maybe) you, who once upon a time called tsuwm mean for a single word correction, are cheating (hmm.. misleading?) us here.
Bats have like us joints, but they have no jointed legs in the meaning of "segmented". And I 'm almost sure that this is what's meant here.
Bats have forelimbs that are developped as wings.
No joints different from other mammals.
"as the structure of the open wing is very similar to an outspread human hand with a membrane between the fingers that also stretches between hand and body."

"Arthropods are characterised by having a segmented body with appendages on at least one segment.
All arthropods are covered by a hard exoskeleton made of chitin."

Mantis leg

Vampire bat