While it may look less threatening than a Carno, Baryonyx is still a very viable choice of mount, especially considering the fact that it’s more maneuverable than a Carno, especially in water, where it can stun anything its size with a tailspin. In addition, due to being a swamp native, leeches will ignore it. Much better mount overall in my opinion, with the only downsides being it’s frail at low levels and fairly rare.
Baryonyx are quick like Allosaurus and do just as much damage (but don't get a pack bonus). They don't use oxygen for swimming and can sprint in the water. Right click in the water does an AoE stun that lasts about 10 sec. Their 'C' is a... Taunt? They also jump and you can fire a weapon from their back.
It's like a small Allo combined with a Kapro, in my opinion. Useful on both land & in the water. Use its secondary attack while swimming to stun, attack, and harvest. Does NOT stun Cnidarias, though, so do not expect to overpower them.