This booklet provides a very detailed review of the splendid perches of the genus Callanthias. With only seven species of brightly coloured fishes in the genus, one might be tempted to think a review is unnecessary at this stage in our understanding of marine fishes. However, given their broad geographical distributions and preference for moderately deep habitats, little is known about this small group and considerable taxonomic confusion is present in the literature. This review provides clarification to that confusion and provides data on some interesting morphological features in the group.
The introduction provides background on the four-decade-long history of the first author's interest in the genus and lists the key morphological features of the group. It also discusses the wider placement of the callanthiid genera (Callanthias and Grammatonotus) among percoid fishes. I would have preferred that the authors included a discussion on some of the more recent genetic studies in this section. However, they have thoroughly covered the morphological hypotheses that exist.
The diagnoses for each species are superbly detailed and provide both external and internal morphological characters. The descriptions are also quite long and detailed, but given the difficulty in identifying species of Callanthias they are reasonable and useful. The key appears to be functional and makes good use of a complicated set of characters from which to choose. I would have preferred to see some colour description and reference to the colour plates in the key. While all of the colour plates are not of the highest quality, they likely represent the best available for such an elusive group.
Following the species descriptions, the authors present a detailed review of the pseudobranchial filaments in Callanthias and devote quite a bit of page space hypothesizing as to the functional role the pseudobranch may play in the physiology of fishes in general. Given that the pseudobranch is not a diagnostic feature of the group or diagnostic among any of the species, this discussion seems a bit out of place and would be more useful in a general book about fish physiology. Nonetheless, it provides an interesting and detailed description of this feature that will be of use to professional ichthyologists.
The discussion of the biogeography of the group is presented in some detail, although records of these fishes are apparently rare enough to make a complete and testable hypothesis. Some of this discussion details the tectonic plates on which each species has been found. I would have preferred to see more modern biogeographic hypotheses invoked and perhaps a phylogenetic framework used to test the authors’ hypotheses.
Overall, this book provides a much-needed and well-executed review of this relatively little-known genus. It will no doubt be a valuable addition to the libraries of any serious student of ichthyology.