I don't know if you've ever seen Eadweard Muybridge's book "Animals in Motion," but he's the father of motion photography. He developed a camera-sorta thing that took action photos in sequence of animals running, (which revolutionized drawing animals in art). Once someone figured out that when you show the photos rapidly in succesion, it looks like it's moving, motion pictures were born.

Anyways, Muybridge has a book called Animals in Motion that shows horses and all that running in sequence. It looks like this except it has horses or cats and etc.
So here's my imitation of that for my made-up creature: this is a myrlaex stride/wingflap in six phases. This is a .46 of a second of time. This is at the begginning of take-off.

I figured that myrlaeda had to have four legs because they need to run fast to get propulsion enough for liftoff. They're as big as horses, so it's difficult to get off the ground. Most flying creatures that size have to leap off a cliff to be able to fly, but not myrlaeda! They just run really really fast.

I designed it to run like a cheetah/greyhound, which would make it hard to ride because the spine is much more bendy than a horses, but oh well.

The top 6 panes is the myrlaex as it would look in real life and the bottom 6 panes has the myrlaex's body outlined in blue so you can see how it's running.
species (c) me.