Mecaenichthys, Whitley, 1929

Tang, Kevin L., Stiassny, Melanie L. J., Mayden, Richard L. & DeSalle, Robert, 2021, Systematics of Damselfishes, Ichthyology & Herpetology 109 (1), pp. 258-318 : 283

Mecaenichthys .

— This is another monotypic genus and its sole representative ( M. immaculatus ) is confined to the coasts of southeastern Australia (Allen, 1991). Historically, it was classified with Chromis and its relatives (e.g., McCulloch, 1929; Whitley, 1929; Marshall, 1964; Allen, 1975a, 1991). Early molecular phylogenies did not support that classification but disagreed on its exact placement within the Pomacentridae ( Tang, 2001; Jang-Liaw et al., 2002; Tang et al., 2004). Koh et al. (2006: fig. 1) did recover it as sister to Chromis cyanea , but putative members of the Chrominae did not form a monophyletic group in their tree. Cooper et al. (2009) reassigned the genus to their Stegastinae [¼ Microspathodontinae ] based on their phylogeny, where it was sister to Parma . Subsequent studies have inferred Mecaenichthys and Parma as sister taxa (e.g., Cowman and Bellwood, 2011; Hofmann et al., 2012; Litsios et al., 2012a, 2012b; Frédérich et al., 2013; Rabosky et al., 2013, 2018; Lobato et al., 2014; DiBattista et al., 2016; Mirande, 2016; Delrieu-Trottin et al., 2019), though Parma is often not monophyletic (see below). Our results did not find the same relationship but did resolve Mecaenichthys within the subfamily, as the sister group of all other microspathodontines. Because both alternatives place it within this group, we agree with Cooper and Santini (2016) in classifying Mecaenichthys as a member of the subfamily Microspathodontinae .