Figure 4
From: Evolutionary and developmental understanding of the spinal accessory nerve
Schematic illustration to show the evolution of the cucullaris muscle. Based on the assumption that the cucullaris first arose through modification of rostral somitic muscle. (A) Comparison of gnathostomes (top) and ammocoete larva of the lamprey (bottom). Note that the infraoptic muscle of the lamprey occupies identical topographical position as that of the cucullaris (hypothetical somitic components) in gnathostomes. (B) Developmental sequence of the infraoptic muscle in the lamprey from Tahara's stages 24 to 28. This muscle is apparently specified by En (LjEnA) expression, which is restricted in ventral moieties of lamprey myotomes. hbm, hypobranchial muscles; ov, otic vesicle. Modified from [82].