The first edition monster manual, and the OD&D sources that predate it, have the traditional mythological liminal beings - centaurs, chimeras, satyrs, sphinxes...

But was David Sutherland's invention of the drider for Q1 in 1980 the first original liminal being in D&D?

By liminal being for this question, I mean something that appears to be quite literally 'stitched together' - part X, part Y.