Rhoda Kellogg's stage of artistic drawing has proposed three stages.
Scribble stage: The scribble is the first stage of artistic drawing in children. This stage occurs in two to five-year children. At this stage, children don't know how to pick the crayons and use the crayons on paper. The drawing is a motor activity and children and children have uncontrolled manipulation. Children used many scribbles such as vertical, horizontal, and diagonal and curving lines. These are around twenty scribbles, seventeen scribbles is used at the primary level.
They're glued to their horses because they're nomadic, so they never completely settle in one place. I have never read Marcellinus before but that seems like the most logical answer. Hope thus helps!