Rapanui Lizardfish

The Rapa Nui lizardfish's dorsal fin usually has 14 or 15 soft rays, while the anal fin has 9 or 10, and the pectoral fins have 12 to 14. The lateral line system is usually made up of 57 to 59 scales, which closely mirrors the number of vertebrae (59 or 60). There are also scales present behind the mouth. Inside the mouth, the anterior palatine teeth are longer than those on the posterior of the palate. In other lizardfishes, peritoneal spots are often used to differentiate species, however S. isolatus has been reported to have anywhere between 1 and 8 spots. This variation has been used to suggest that peritoneal spots may not be as useful tools for differentiating lizardfish species as previously thought.

Despite being generally observed in the shallows, the Rapa Nui lizardfish's habitat spans a broad range of depths ranging between 10–250 m (33–820 ft). When observed at a depth of 150 m (490 ft), the fish appeared to prefer rocky and sandy bottoms. Individuals collected from deeper depths tend to show a distinct reddish color, but otherwise possess the same features as shallower-dwelling members of the species. Fishes from Easter Island usually tend to be depth-tolerant, which may be due to the low species diversity in this area and the limited amount of geographic space for shallow-adapted fishes to occupy.