The main crocodylomorph in Planet Dinosaur is the Sarcosuchus.
Lost World:
In Lost World a crocodylomorph is seen when the Spinosaurus scares it into the Onchopristis River. Later in the episode, another crocodylomorph is seen basking on the bank. The Spinosaurus roars at the crocodylomorph and a huge Sarcosuchus is awoken from a deep sleep. The Sarcosuchus wards both the crocodylomorph and the Spinosaurus off before returning to sleep. No more crocodylomorphs are seen in Lost World.
New Giants:
When a Paralititan is mired in mud, a group of crocodylomorphs emerge from the river and stalk it. However, when a huge Sarcosuchus scatters the crocodylomorphs, the Paralititan's case is truly dire. However, a Carcharodontosaurus appears and the two giant killers play a deadly tug-of-war game with the juvenile sauropod. The Carcharodontosaurus eventually wins and the Sarcosuchus retreats back into the River of Giants.
Trivia:
1. Sarcosuchus is the largest crocodylomorph in Planet Dinosaur.