FishFace

By 516 hpf, the ceratohyal (ch) has grown in size considerably from that seen at 342 hpf, although the medio-lateral thickness at the middle region remains one cell layer. Articulations of the ceratohyal with the interhyal (ih), the contralateral ceratohyal, and branchiostegal rays 1, 2, and 3 (bsr1, bsr2, bsr3) are visible. The four bones of the ceratohyal perichondrium now almost cover the cartilage completely: the ventral hypohyal (hhv) and dorsal hypohyal (not shown) along the anterior end, the ceratohyal bone (chb) along the middle region, and the epihyal (eh) at the posterior end. Also forming in some specimens is branchiostegal ray 4 (bsr4), which articulates with the medial aspect of the ceratohyal bone anterior to branchiostegal ray 1.