We all know how to tame a ptera by now, bola and pop it in the head with either a club for low levels or tranq arrows for high ones; but the real tip here is to use chitin for the saddle instead of keratin. 75 keratin is difficult to find quickly, but chitin is available via just about any bugs or other invertibrates, and they tend to drop a lot of it. One trilobite could probably net you all of the chitin you need, especially when carved by something like a moschops.