Monday, February 24, 2014
Brochoadmones came from the Early Devonian of Canada, about 435-430 million years ago. Around 10cm long (4in), it was a type of “spiny shark" — an extinct group that shared features with both bony and cartilaginous fish.
And it had a lot of extra fins. Six paired “finlets” running from below the gills to the pelvic fins, each consisting of a spine with a web of scaled skin. They look very much like what would be expected for multiple fins evolving from a lateral fin-fold (essentially a single elongated fin subdividing).