Fig. 4
From: Development of hypobranchial muscles with special reference to the evolution of the vertebrate neck
Developmental sequence of HBMs. a-h, 3D reconstruction images of shark (a-d) and lamprey (e-g) embryos from lateral view. (d) Anterior view of (c) with translucent ventral aorta. Somites developed ventrally sending HBM precursors (arrowheads) lateral to the pericardial mesoderm in both species (a, b, e and f). HBM precursors developed inward being surrounded laterally and ventrally by mandibular and hyoid muscles in sharks (c, d), whereas the precursors extended outside the branchial muscles and skeletons in lampreys (g, h). Somites detached from HBM precursors (c) and right pharyngeal muscles (d) are not shown. ba, branchial arch mesoderm; ba1, first branchial arch mesoderm; bb, branchial basket; bm, branchial muscles; es, endostyle; ha, hyoid arch mesoderm; hc, hypoglossal cord; ih interhyoideus; im, intermandibularis; ma, mandibular arch mesoderm; nc, notochord; nt, neural tube; ot, otic vesicle; pcm, pericardial mesoderm; so, somites; thy thyroid gland; IX, glossopharyngeal nerve; X, vagus nerve