P. yunnanensis

(Fig. 4):

1.

The top of the arcs is slightly pointed, and the arc mouth is relatively open. 2. The arc mouth corresponds to two or more rows of neatly arranged pore structures. 3. The pores in the arc are mostly arranged in a “conical” shape, where the top part of the arcs exhibits one pore, followed by two pores. 4. The axis of the wavy lines formed by multiple arcs shows wavy fluctuations; in each field of vision, there are many groups of such lines, and each group intersects with others. The microornamentation of the snakes exhibits a common feature: the distance between the wavy lines in each group is much longer than the height of an arc.