Lateral view of head muscles of a ‘myological stage 3.5’ newborn lamb. Left (A) and right (B) sides of specimen 122B, showing a condition between myological defective stages 3 and 4 (paper square = 1 cm). This specimen shares some traits with stage 3 lambs (e.g. very marked face/snout truncation, left and right muscle asymmetries, ‘nasal proboscis’ mainly situated on right side of head) but is more defective than stage 3 lambs because only one of the three small anterior facial snout muscles in present in both sides of the head - the levator labii superioris. For more details see text and SI1 Table 1.