The Predalien Chestburster appeared in the final scene in 2004’s Alien vs Predator and at the start of 2007’s Aliens versus Predator Requiem. You can read about an adult Predalien here.
The Predalien Chestburster is a similar shape to a normal Chestburster but as the creature comes from a Predator, it takes characteristics from its host. In this case, it has mandibles.
For hundreds of years, Predators have been using Antarctica as a hunting ground for young Predators to prove their worth. In 2004, the Predators burn a hole in in the ice to an underground pyramid which catches the attention of Peter Weyland. He organises an expedition to investigate it. As they explore the pyramid, a chained Queen is forced to lay eggs with Facehuggers which infect members of the team. The three Predators go down there to hunt the aliens and the expedition team get caught in the crossfire.
Chopper and Celtic Predator are a killed and at one point, Scar Predator was attacked by a Facehugger. Later, Lex and Scar Predator team up with each other and try to escape the pyramid. On the surface, they battle the Queen but Scar is impaled on her tail. Lex is the remaining survivor and the Elder Predators appear and take Scar away onto their ship. On the mothership, a Predalien Chestburster bursts out of Scar Predator.
The Predalien Chestburster quickly molts into an adult Predalien. It sneaks onto a scout ship and kills a few Predators. In the chaos, the scout ship crashes back to Earth, releasing the Predalien and several Facehuggers.
Amalgamated Dynamics, led by Alec Gillis and Tom Woodruff, was hired to do the creature effects on Alien vs Predator and its sequel. When director Paul W.S. Anderson was trying to make his pitch for AvP, he hired artist Patrick Tatopoulos to make some concept art to support him. To the right, you can see one piece showing the Predalien Chestburster which is similar to what was ultimately made for the film.
Trivia: In a deleted scene which was seen in the script and behind-the-scenes stills, Scar Predator knew there was a Chestburster inside of him when he was killed by the Queen Alien and he signalled to Lex to kill him.
In Aliens vs Predator Requiem, A.D.I. re-created the opening scene where the Predalien Chestburster emerges from Scar Predator.