Batrachoidiformes are benthic fishes that build spawning nests in intertidal rocky habitats. These species, which produce large eggs that are protected by the parents, lack larval dispersal. Rather, their larvae are attached to the nest and are nourished by their large yolk sac. The shift from a feeding, free-swimming to sedentary larva can lead to changes in skeletal development, especially in those structures associated to feeding and locomotion, which are typically among the earliest elements to form in teleostean larvae. To assess such changes, an ontogenetic series of Plainfin Midshipmen, Porichthys notatus (5 to 28 mm TL), was collected and cleared-and-stained to observe ontogenetic changes in the skeleton. In P. notatus the ossification of feeding-related bones, such as pharyngeal tooth plates, occur relatively later than in other percomorphs with free-swimming larvae. We observed that the single cartilaginous element positioned posterior to basibranchial three does not belong to the basibranchial series. In early stages (6.8-7 mm NL), hypobranchial four (HB4) is present and distinct as a pair of elements. Around 7.5 mm NL, the paired HB4 fuses into a single median element positioned posterior to basibrachial three; it remains cartilaginous and distinct in adult stages. The morphological similarity of this median element across the diversity of Batrachoidiformes suggests that having the left and right HB4s fused into a single cartilage has occurred in the entire order. Implications of this and other characters of the ventral gill arches of Batrachoidiformes will be discussed.