Sea chubs are widespread reef inhabitants of tropical and temperate reefs, but the relationships and taxonomy of the 16 valid species (Hermosilla,
Kyphosus, Neoscorpis and Sectator) are confused because of problems with character differentiation. We undertook a molecular phylogenetic
study using complete taxon sampling from these fishes, and species delimitation was determined on the basis of congruence between
monophyletic groupings in the molecular phylogeny combined with comparison of morphological variation in type material. The results overall
indicate that our understanding of species diversity and higher level relationships require revision.
Topologies including a range of outgroup taxa consistently failed to retrieve a monophyletic Kyphosidae sensu Nelson (2006), i.e. Kyphosus +
Girella + Scorpis. Our work thus supports previous phylogenetic studies in suggesting that Kyphosidae, Scorpididae and Girellidae be considered
separate families. Both Hermosilla and Sectator are now considered junior synonyms of Kyphosus. The distribution of Kyphosus species was
reconsidered based on the taxonomic revision, indicating that four species (K. bigibbus, K. cinerascens, K. sectatrix and K. vaigiensis) are found
in both the Atlantic and Indo-Pacific regions. The Hawaiian K. sandwicensis was found to be a junior synonym of east Pacific K. elegans. The
Atlantic endemic Kyphosus incisor and the eastern Pacific K. analogus were found to be conspecific with the Indo-Pacific K. vaigiensis.
Kyphosus gallveii, only known from Saint Helena, and the Pacific K. pacificus and K. lutescens, the latter endemic to the Revillagigedo Islands
in the east Pacific, were found to be conspecific with K. sectatrix, previously considered an Atlantic endemic. A higher number of gill rakers was
found to be characteristic of all tropical species, suggesting this character changed in response to the invasion of low latitude reefs – perhaps as a
response to a change in diet from large sub-tropical macroalgae to smaller algal growth on tropical reefs. Furthermore, careful examination of
multiple molecular markers and a re-examination of morphological variation confirmed that a previously unrecognised species (Kyphosus
gladius sp. nov.) had been clumped with Kyphosus sydneyanus in Western Australia. Overall, the family contains fewer species (12) than
previously thought, but four of these species are considerably more widespread than expected