Analogues: (solitary post-anal-fin spot) Pre-transitional larvae before they develop basicaudal scales can only be distinguished by modal fin-ray counts (12/11 p-16) from many other species: Gobiosoma spes has mostly 12/10, Risor ruber and G. hildebrandi (Panama) have mostly 11/10. The eyes on this larval type are smaller than those of many related species. Many individuals have basicaudal scales; these are absent from other larvae (uncertain for G. hildebrandi (Panama)). Risor ruber larvae do not have the basicaudal scales at transition, but do have distinctive spiny scales along the ventral midline of the caudal peduncle. Evermannichthys larvae also have ventral midline scales along the caudal peduncle, along with a very pointed snout and and low pectoral-fin ray counts. Psilotris batrachodes larvae have divided pelvic fins and only 7-8 anal-fin elements. Psilotris alepis larvae have divided pelvic fins, a wider caudal peduncle, and a pelvic-fin base spot.
Description: Body relatively thin, long, and narrow with a medium eye and a terminal medium mouth. Pectoral fins long, reaching to or past vent. Pelvic fins medium, extending about two-thirds the way to the vent, with a flat frenum not forming an obvious cup. Dorsal and anal-fin bases medium length and caudal peduncle medium length and width, procurrent caudal-fin rays usually 6 (5-6 spindly). A single melanophore on the caudal peduncle ventral midline just after the last anal fin and internal melanophores only at the dorsal surface of the swim bladder and sometimes around the gut near the vent. The eye is slightly vertically-narrowed and has a coarsely-speckled membrane overlying the upper iris. Many larvae have a pair of large spiny scales on the tail over the base of the uppermost and lowermost segmented caudal-fin rays. Transitional larvae first develop a sparse scattering of small discrete melanophores on the upper head, then a pair of melanophores behind the tip of the upper jaw, a few on the anterior upper jaw and an incipient stripe from the eye to the mid upper-jaw.
Diagnosis: Fused pelvic fins and modal fin-ray counts of D-VII,12 A-11 and Pect-16 and fused pelvic fins match the Elacatinus cleaner gobies as well as overlapping the reported upper range of T. gemmatus (and T. macrodon from Florida to Haiti) and Gobiosoma spes. In US waters, several Gobiosoma species also fit this fin-ray count. Many larvae of this type in Panama have a pair of spiny basicaudal scales (ruling out the cleaner gobies and G. spes), leaving only T. gemmatus. In Panama, 2 out of 3 larvae of this type have 12/11 p-16 (remainder mostly 12/10). G7S1211
