I don't think I've heard of the masher prior to reading about The Sea Wyvern's Wake (I looked at 1e MM the other day at Half-Price Books and found the entry, so I must have skipped over it) and I only dimly remember the rhagodessa. Who decided to convert these monsters for The Savage Tide? Was it the authors or the editors? And why?
Can we expect some more obscure conversions in upcoming modules? I do love the conversions (though I hope to see a living shipwreck in an upcoming episode of the AP).