A bit of information on the creases.
The Zygote map you were looking at is a bit simplified. I was curious and took a look at an anatomy book (anatomy for sculptors) myself to see what was going on. The trapezius actually looks like two diamonds with a rectangle attaching them. One big one that connects the neck to the edge of the Scalpula. And also attaches to the spine. The diamond on the neck is a formation of tendons in which the muscle is attached to. So those are flat. And the bump is the 7th vertebrae. The trap is connected to the spine of the scapula on the top to a certain point. And partly on the edge. And the shoulder blade is covered by the Rhomboid muscle.