“…Included in this category are: - Neck muscles, which evolved from muscles initially associated with early gill and appendicular structures (Ericsson, Knight, & Johanson, ; Ziermann, Freitas, & Diogo, ),
- Muscles of facial expression, which are derived from 2nd BA myoblasts (i.e., hyoid arch; Gasser, ) and are unique to mammals,
- Laryngeal muscles, whose ancestry has been controversial (Edgeworth, ),
- Muscles associated with the soft palate, which are derived from branchial arches 1 and 4 and are innervated by both trigeminal (CNV) and vagus (CNX) nerves, respectively, and
- Skeletal muscle cells that envelop the caudal pharynx and in some mammals circumscribe the esophagus. Striated myocytes are present in the external esophageal muscle layers around most (dog, pig, mouse) or part (horse, cat, human) of the length of the esophagus, but are absent in birds (reviewed by: Shiina et al, ). Progenitors of these cells are added to the cranial portion of the elongating esophagus (Rishniw, Xin, Deng, & Kotlikoff, ) and are derived from cardiopharyngeal mesoderm (Gopalakrishnan et al, ; reviewed by: Krauss, Chihara, & Romer, ).
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