Protoxeno second jaw

Hi I have studied the gif when the protoxeno or whatever its called (the last alien we see), unleash its second jaw. For me it looks like its the first time its develop the second jaw. The way it pushes itself out, and you can clearly see that its not a complete jaw, but the first stage for something to soon become a jaw. Like it is "new" also for the alien. the first result of some mix. What u guys think about it? I