Like you, Maltrix, I appreciate that the "canon" beasts we've seen so far are reasonably consistent with what's mentioned in the textbook entries you've highlighted.
Good catch noticing that Yates confirms there's a Murtlap in the film, even if he doesn't comment on the streaking-from-suitcase critter.
The "Murtlap tenticles" that grow on its back (where all the still clips I've made of the streaking critter suggest there is indeed something there) are valued in potions, but overdose can turn earhair purple. So may make sense for the coloration to be in the pink-purple range? Here's some art that seemed plausible to me (the old Pottermore showed the tenticles as grren and purple) and somewhere in the ballpark of the still frames I've made of the streak, tho what's in the trailer seems furry in the non-amemone parts of it:
Concerning the Billywig, the more I look at the translucent thing in the speakeasy, the more it appears to my eye to resemble a translucent (why? how?)Billywig:
Of course, the view we get of the thing floating in the speakeasy is fron the side, while we see the fully embodied Billywig from above. But what's puzzling/implausible about that hypothesis (besides them being translucent...) is that Scamander's textbook tells us Billywigs are bee-sized, not 1-3 feet long.
What do y'all think? Are we meeting ghosts /something new?
