Spizelloides, gen. nov.

Type species. Fringilla arborea Wilson, currently Spizella arborea .

Included species. Spizelloides arborea (Wilson) comb. nov., American Tree Sparrow.

Diagnosis. Distinguished from all extant species of Spizella, Passerella, Junco, and Zonotrichia by (1) a yellow lower mandible contrasting with a black upper mandible and (2) strongly divergent molecular characters (Klicka et al. 2014). Further distinguished from the six species of Spizella — atrogularis (Cabanis), breweri (Cassin), pallida (Swainson), passerina (Bechstein), pusilla (Wilson), and wortheni (Ridgway) —by (1) distinctive plumage features including rufous crown, rufous postocular stripe, and pale gray underparts with a dark central breast spot; (2) larger size on average (wing chord 67–82 mm, tail 60–74 mm; Pyle 1997); and (3) lateroventral process (LP) of the laterosphenoid 0.8–1.3 times the length of the zygomatic process (ZP) and with a wide, flat tip (vs. LP short (0.1–0.4 times the length of the ZP) in five species of Spizella; S. wortheni not examined; Patten & Fugate 1998). Further told from Passerella iliaca, its sister taxon according to the most complete molecular phylogeny (Klicka et al. 2014), by plumage characters, including a conspicuous lack of dense, dark streaking or spotting on the underparts. Separated from all extant species of Zonotrichia — atricapilla (Gmelin), albicollis (Gmelin), capensis (Müller), leucophrys (Forster), and querula (Nuttall) —and Junco — hyemalis, phaeonotus (Wagler), and vulcani (Boucard) —species by rufous crown and, in adults, a combination of dark iris and dorsal plumage streaking.

Description. Spizelloides arborea is well known and many descriptions have been published elsewhere (e.g. Ridgway 1901; Naugler 1993; Pyle 1997).

Etymology. The generic epithet Spizelloides is formed from the sparrow genus Spizella and the Greek suffix -oidēs (resembling; Brown 1956). The name alludes to the evolutionary convergence in plumage, morphology, and behavior that led to Spizelloides arborea being considered a Spizella sparrow for many years. The gender of Spizelloides is feminine.