Rhagologus, Stresemann & Paludan, 1934

Schoddei, Richard & Christidis, Les, 2014, Relicts from Tertiary Australasia: undescribed families and subfamilies of songbirds (Passeriformes) and their zoogeographic signal, Zootaxa 3786 (5), pp. 501-522 : 509

3. Rhagologus

Despite its streak-plumaged females, New Guinean Rhagologus has traditionally been included in the family Pachycephalidae (Australasian whistlers) because of its whistler-like appearance (e.g. Salvadori 1876; Mayr 1941, 1967; Rand & Gilliard 1967; Sibley & Monroe 1990; Dickinson 2003; Boles 2007a). Early DNA-DNA hybridization work ( Sibley & Ahlquist 1982, 1985, 1990) lent support to that presumption. Nevertheless, all five multi-locus DNA sequence studies that have screened Rhagologus ( Jønsson et al. 2007, 2010, 2011; Norman et al. 2009b; Aggerbeck et al. 2014) place it firmly elsewhere, among a complex of corvoid songbirds that includes the Australasian butcherbirds and woodswallows ( Artamidae ), African bush-shrikes, wattle-eyes and vangids ( Malaconotidae , Platysteiridae , Vangidae ), southeast Asian ioras ( Aegithinidae ) and Old World cuckoo-shrikes ( Campephagidae ). Nearest relatives within that complex are still unclear. The ioras ( Jønsson et al. 2011) or the cracticid-artamid group ( Aggerbeck et al. 2014) have been indicated, but support values are weak, and depth of divergence considerable.

As diagnosed, frugivorous Rhagologus has little in common with the insectivorous ioras, which are predominantly yellow-, green- and black-plumaged with silken-plumed flanks, display aerobatically and build perched cup-shaped nests bound smoothly with cobweb. Nor do its rather broad palate, open nares and unstructured temporal region of the skull resemble the narrowed palate, heavily ossified nasal cavity and compound zygomatic processes found in the Australasian butcherbirds and woodswallows ( Schodde & Mason 1999: 533) and, in part, vangas. The insectivorous pachycephalids have a broad palate and internally perforate nasal cavity similar in form to those of Rhagologus , but the temporal region of the skull differs markedly: its fossa is much narrower, deeper and more clearly defined in pachycephalids, and both postorbital and simple zygomatic processes are well-developed and directed ventrally at an angle of c. 45º. Combined morphological, behavioural and DNA sequence evidence reveal Rhagologus as a deeply divergent corvoid lineage that cannot be placed in any other family. Accordingly, it is described at family rank here.