Kelloggella centralis, Hoese, 1975

described K. centralis View in CoL , which was later synonymized with K. quindecimfasciata by Winterbottom and Emery

(1986). Hoese (1975) also considered K. quindecimfasciata to be a synonym of K. oligolepis , but Sawada (1977) subsequently considered both to be valid species. All species of Kelloggella are small, even among gobies (typically <30 mm total length), and occur exclusively in tide pools and high-energy exposed reef flats that are rarely sampled. These factors, coupled with their cryptic behaviour, contribute to specimens being rare in collections. The genus is widely distributed from the Chagos Archipelago in the west to Easter Island in the east, although records are sporadic throughout this range. Larson (1983) studied the ecology and behaviour of K. cardinalis in Guam and noted that even in suitable habitat, the species was not common and had a patchy distribution around the island. Similar to many other tide pool inhabitants, K. cardinalis can tolerate extreme fluctuations in salinity and temperature. In Guam, individuals were found in pools with salinities as low as 1.1 ppt and as high as 42 ppt, and with temperatures reaching 39 °C ( Larson, 1983).

The phylogenetic position of Kelloggella within Gobiidae is unclear. Both Gosline (1955) and Hoese (1975) studied the osteology of Kelloggella but neither made specific hypotheses regarding phylogenetic affinities. In a survey of gobioid vertebral osteology, Birdsong, Murdy & Pezold (1988) placed Kelloggella in a group by itself based on the unique vertebral count of 11 precaudal and 15 caudal vertebrae, coupled with relatively uncommon presence of a single anal-fin pterygiophore (vs. two or more) inserted before the caudal vertebrae. Thacker & Roje (2011) analysed phylogenetic relationships with Gobiidae using sequence data from mitochondrial and nuclear genes, but their analysis did not include Kelloggella . Nonetheless, in an attempt to provisionally classify all genera in Gobiidae , they tentatively placed Kelloggella in the ‘coral goby’ group, which was represented by Eviota , Gobiodon and Bryaninops in their molecular tree ( Thacker & Roje, 2011). That provisional decision was based on the diminutive size of Kelloggella and an alleged superficial similarity to Eviota , although no specifics were given regarding the morphological similarities. The monophyly of the ‘coral goby’ group of Thacker & Roje (2011) has been supported by three subsequent molecular phylogenies ( Agorreta & Rüber, 2012; Agorreta et al., 2013; Tornabene, Chen & Pezold, 2013), but all studies to date have had very limited taxon sampling within the ‘coral goby’ group and none included Kelloggella .

Comprehensive and detailed taxonomic descriptions often provide information that is invaluable for future comparative morphological/phylogenetic studies, as well as those on the ecology, biogeography and macroevolution. Recently, material has become available that facilitates such a study on Kelloggella . During a recent trip to island nation of Nuie in the Central Pacific Ocean, a series of specimens and live photographs of an undescribed species of Kelloggella were obtained while sampling tidepools in search of specimens of Eviota . In addition, we obtained tissue samples from a new series of specimens of K. oligolepis from Hawaii, and from a series K. disalvoi from Easter Island, which now enable us to infer the phylogenetic position of the genus using molecular data. Collectively, we take advantage of these new sources of material to provide a detailed description of the new species, Kelloggella avaiki sp. nov. We expand on the published information on the osteology of Kelloggella through observations of cleared and stained specimens of K. oligolepis and the new species and briefly compare their morphology with other gobiids including those hypothesized to be close relatives based on the molecular phylogeny.