Toxorhamphus, Stresemann, 1914

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 : 504-505

Toxorhamphus and Oedistoma

Historically, New Guinean Toxorhamphus has been linked with the paleotropic sunbirds ( Nectariniidae ) because of superficial similarities to the spiderhunters, Arachnothera ( Gadow 1884; Dorst 1952), and to the Australasian honeyeaters ( Meliphagidae ) with which it shares a quadrifid, brush-tipped tongue, slit-like nostrils and long bill ( Stresemann 1914; Scharnke 1931, 1932; Salomonsen 1967; Wolters 1979; Bock 1985). Similarly, for most of the 20 th century, New Guinean Oedistoma was placed among the Australasian honeyeaters and, following Salomonsen (l.c.), treated as a sister genus of Toxorhamphus , which it resembles in form and plumage ( Rand & Gilliard 1967; Beehler et al. 1986; Coates 1990).

DNA-DNA hybridization studies ( Sibley & Ahlquist 1985, 1990) associated both genera with the New Guinean berrypeckers ( Melanocharitidae ) instead, in a cluster placed sister to the sunbirds and flowerpeckers ( Dicaeidae ). Since then, DNA sequencing studies ( Barker et al. 2002, 2004; Driskell et al. 2007; Jønsson et al. 2011; Aggerbeck et al. 2014) have confirmed a close link between Toxorhamphus , Oedistoma and the Melanocharitidae , but nevertheless have found the complex to form a monophyletic group that is basal among corvoid and passeridan birds. Sibley & Monroe (1990) placed Toxorhamphus and Oedistoma in the tribe Toxorhamphini , and Melanocharis and Rhamphocharis in the tribe Melanocharitini . In contrast, Christidis et al. (1993) recovered Oedistoma sister to Melanocharis-Rhamphocharis from allozyme variation at 18 presumptive protein loci, with Toxorhamphus basal to both lineages. Furthermore, the branches between Oedistoma and Toxorhamphus in DNA sequence phylogenies (e.g. Barker et al. 2004; Jønsson et al. l.c.) are almost as deep as those between them and Melanocharis .

Morphological and behavioural features reinforce the distinctness of Toxorhamphus and Oedistoma and their links with Melanocharitidae . Although both genera have long, decurved bills and quadrifid, brush-tipped tongues for harvesting nectar, the fine structure of these organs differs markedly, indicative of different mechanisms for nectar uptake. Uniquely modified for capillary action, the tongue in Toxorhamphus is a slender tube, with a bowl at the base (presumably for holding nectar) and has a shallowly quadrifid tip in which the medial furcation is shallower than the two lateral. The four lobes of the tip, moreover, are terminally truncate and serrately toothed on the outer margins only (see subfamily diagnosis). In contrast, the tongue of Oedistoma is deeply brush-tipped and honeyeater-like and fitted for nectar-mopping instead. It differs from the basic form of the honeyeater tongue only in its more in-rolled sides and reduced laciniations on the medial lobes of a deeply quadrifid tip. The tongues of Melanocharis and Rhamphocharis are short and open in comparison, and barely fibriate at the tip. The shorter bills of Melanocharis and Rhamphocharis also bear a unique series of broad, evenly-spaced notches along the maxillary tomia; mandibular tomia are almost smooth. Oedistoma instead has the same pattern of fine tomial toothing on both maxilla and mandible as do sunbirds, except that the tubercles are aculeate, coarser and more widely spaced. Toxorhamphus differs in having both maxillary and mandibular tomia set with the same fine, close-packed tuberculate teeth as in sunbirds, but on the maxilla the teeth are laid out on stepped notches. The notches are more spaced out and shallower than those in short-billed Melanocharis , but their intermediate state on longer-billed Rhamphocharis suggests that all may be homologous. Such geometrically exact integumentary structures are missing from the coarsely and irregularly serrate bills of honeyeaters.

Although in Toxorhamphus the configuration of the fossa at the head of the humerus is essentially single, the decurrent incisura capitis is developed into an incipient inner fossa, trending toward the double condition. In Oedistoma (n = 1), the inner fossa is even deeper and the outer shallower, still closer to the double condition. Melanocharis and Rhamphocharis all have fully double humeral fossae. Toxorhamphus , Oedistoma and Melanocharis also build distinctive nests of similar form ( Mayr & Gilliard 1954; Parker 1963; Coates 1990; data in ANWC). Their nests are neat, smoothly-bound cups thickly lined with a felt of plant down and structurally different from the rough twig nests of honeyeaters or coarse, pendant, variably hooded nests of sunbirds. Yet whereas those of Toxorhamphus and Melanocharis are perched on branchlets and decorated with spider egg sacs, the only reliably recorded and preserved nest of Oedistoma was hung from the rim and decorated with small leaves ( Rothschild & Hartert 1896). There are also basic differences in egg pigmentation between Toxorhamphus and Oedistoma (see subfamily diagnoses). The “unmarked white” eggs of Toxorhamphus poliopterus recorded in Mayr & Gilliard (1954) and Coates (1990: 312) appear to be misdescribed; their description is here emended from material in ANWC.

Differences in structural morphology and nest-building described above, considered collectively with DNA sequence data, indicate that Toxorhamphus and Oedistoma are sister to the berrypeckers yet still deeply divergent from them and one another. Accordingly, we place them here in separate subfamilies within the Melanocharitidae , noting that their depths of DNA, morphological and behavioural divergence may be found to qualify them for family ranking in the future. Although Sibley & Ahlquist (1990: 669) and Sibley & Monroe (1990: 669) earlier used the name Toxorhamphini , they provided no description, publishing it as a nomen nudum (Articles 13.1 and 13.2.1 of the Code). The berrypecker genera Melanocharis and Rhamphocharis are here placed in the nominate subfamily, Melanocharitinae Coates, 1990.