Xenacanthus

Xenacanthus is an extinct genus of freshwater sharks that existed from the Devonian to the Triassic. The actual length would have been around 1-2 m/3-6 feet. I've decided to give this thing a strong green coloration, even though I'm not aware of any green cartilaginous fish currently in existence. I guess it might make some sense for a freshwater ambush hunter to be the colour of weeds. If I had to bet on it I'd say it was probably more likely to have been some shade of brownish in real life, but I wasn't happy with that paint job.
I've also included the unpainted model because I've only just started printing in resin and am still amazed at the level of detail.