i think it's just a fin nip. he doesn't have any of the other signs of doubletail genes (widened dorsal, thicker body) plus it's supposed to be next to impossible to successfully mix DT and CT genes.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
'Cause there's bugger-all down here on Earth.
Loki/Grendel/Gail/Beowulf/Camilla/River/Bathory/Arwen/Lafayette/Deb/Jack Skellington (soon)