You get smaller, as all creatures do when they leave the sea. However, as a hunting creature you can’t afford to get too small.

You experience a few changes, over the course of the next few hundred million years: one lucky gene error gives you the ability to express venom. This rapidly causes a stinger to evolve at the end of your tail. Another gives you the ability to express a sticky substance on your feet, which helps you climb and capture and hold prey. Similarly, your pedipalps[1] grow bigger and stronger.

This takes an awfully long time, and gets you through more than one extinction event virtually unchanged, but eventually, around 100 million years ago, you need to specialise to survive. You can make a bigger, stronger, stinger to chase down your prey, or you can make stickier silk, and wait for something to come to you.