Analogues: The 10/10 sand goby clade share fin-ray counts, morphology, and most markings as larvae and new recruits. C. tortugae and the other head-striped sand gobies develop short stripes on top of the head very early in transition, separating them from the spotted-head gobies (i.e. C. eidolon, C. thrix, C. alloides, C. kuna, and the non-sand Coryphopterus species). C. tortugae begin to diverge when they develop a cluster of melanophores below the eye at 6-7 o'clock on the orbital rim (i.e. under the anterior pupil) vs. at 7-8 o'clock (and then continuing as a line across the upper jaw to the tip) on C. glaucofraenum. C. bol share the cluster under the eye and only diverge from C. tortugae when they develop melanophores on the lower third of the pectoral-fin base (absent on C. tortugae) and then a complete long upper eye-stripe (broken on C. tortugae); note that these long surface eye stripes overlie the short eye stripes of the transitional stage. C. tortugae develop a basicaudal bar, notably without the rounded colon-like spots on the base of the caudal fin as seen on C. glaucofraenum.
Diagnosis: Modal fin-ray counts of D-VI,10 A-10 and Pect-18-20 with fused pelvic fins indicate the 10/10 Coryphopterus sand gobies, i.e. Coryphopterus tortugae, C. glaucofraenum, C. dicrus, C. eidolon, and C. thrix. The distinguishing features of adult C. tortugae are mostly not present on recruits and small juveniles.
