Description: Body thick, long, and somewhat narrow with a small eye and a terminal large wide mouth. Head broad and slightly flattened. Pectoral fins relatively long, reaching much of the way to the vent. Pelvic fins short, extending less than halfway to the vent and fused with a small frenum (some larvae show split pevic fins that are artifacts). Dorsal and anal-fin bases short, caudal peduncle relatively wide and long and procurrent caudal-fin rays 8-10 (8-9 spindly). Melanophores on the head are limited to at the angle of the jaw and sometimes on the inner (mouth) side of the lower jaw. Characteristically, there is a large melanophore or two overlying the cleithrum just behind the operculum and just forward of the pectoral-fin base. This melanophore can be absent on very lightly-marked individuals. Lightly marked, mostly along the ventral midline: at the isthmus, just forward of the pelvic-fin insertion, then sometimes on the abdomen just behind the pelvic-fin insertion, then three or four melanophores spaced along the anal-fin base (often paired, one per side) and then a row (or streak) of three or four extending along the caudal peduncle ending near the start of the procurrent caudal-fin rays. The abdominal melanophores are quite variable, missing in some individuals and a clear Y-shape diverging from the pelvic-fin insertion in others (post-pelvic Y). Melanophores are present on the base of most of the lower caudal-fin segmented rays extending up to halfway along the rays. There are internal melanophores around the sacculus, on the dorsal surface of the swim bladder, and around the gut near the vent. Series of transitional larvae show that the eye develops from a slightly narrowed vertical oval, sometimes tilted forward, to larger and round. Transitional larvae always have the melanophore overlying the cleithrum just forward of the base of the pectoral fin, and often more around the base of the pectoral fin. Melanophores then develop as a scattering in a vague stripe on the body underlying the pectoral fin rearwards. In addition, there can be melanophores on the inside of the mouth at the tip of the lower jaw and a few tiny ones around the maxilla.
Diagnosis: Fused pelvic fins and modal fin-ray counts of D-VII,10 A-9 and Pect-16-17 indicate Barbulifer species. Other seven-spined gobies with this modal fin-ray count have divided pelvic fins and include Pycnomma roosevelti, Psilotris, and Chriolepis. Gobiosoma grosvenori shares the fin-ray counts and should have a mostly-divided pelvic fin but, since the rest of the Gobiosoma have typical fused pelvic fins, the pelvic fin in larval G. grosvenori may not be divided (it also occurs only in Florida and Venezuela). This larval type, however, has the shape characteristic of Barbulifer, i.e. a large broad and flattened head, a wide mouth, a short pelvic fin with a frenum, and a wide caudal peduncle. There are two Caribbean species with the same fin-ray counts: B. ceuthoecus and B. antennatus. The latter is not reported from Panama. The remaining seven-spined gobies all have a mode of more than 10 second-dorsal-fin elements. (PE) G18
