A displacement map does exactly what the word says. It "displaces" and it is a "map".

Displacement = It moves the texture outwards following the direction of the normals. And it depends on the units you are using in Poser.

It is a map = Pixels. => And Pixels are little squares.

So: A displacement map, displaces pixels to an amount set by the node and the units used.

To get rid of what you see you can do 2 things.

a) Reduce the amount of the displacement
b) Make the pixels smaller. => Use a larger map.

Maps can be:
512x512 => Large pixels, heavy saw tooth effect
1024x1024
2048x2048
4096x4096
8192x8192 => Small pixels, little to no saw tooth effect.

The larger the map size, the smaller the rendered pixels will be, and the smaller the saw tooth effect will become.

So?
•Reduce the amount of displacement in the node
•Blur the edges on the map
•Or use a larger size map