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Let's fix those pterosaur hands - PS


On second thought, I made a mistake in suggesting that Chris Bennett advocates folding the pterosaur hand in half and gluing it back-to- back. That's just the result of his hypothesis when translated into reality. He illustrates this in his figure 5.

Instead Bennett advocates supinating the antebrachium and with it the entire hand. He also advocates changing the natural flexion of digit IV into the hyper-hyper-hyper-extension of digit IV so that the digit can fold back-to-back along the backside of its own metacarpal.

In consideration of this, if the entire hand supinates thumbs up, then to achieve Bennett's configuration of metacarpals I-III backed up and "bound" to metacarpal IV, somehow the lateral bond between III and IV has to break and metacarpals I-III have to slide as a unit down Bennett's "palmar" side of metacarpal IV, coming to rest with the former lateral side of III nearing the former lateral side, now the underside, of IV. Bennett's figure 6 stops short of showing this.

In addition, if Bennett is correct, all former hallmarks of the dorsal surface of metacarpal IV - via evolution - become ventral in morphology and vise versa without leaving a trace of their former identity.

Sorry to introduce more problems. Nothing about this hypothesis seems tenable.

David Peters
St. Louis