The oleaginous hemispingus (Hemispingus frontalis) is a species of bird in the family Thraupidae. It is found in Colombia, Ecuador, Peru, and Venezuela. Its natural habitats are subtropical or tropical moist montane forests and heavily degraded former forest.
The species’ underparts are dull-yellow in colour while it upperpart is olive-green.
The Oleaginous Hemispingus is a rather dull-colored member of its genus, predominantly dull yellow below and olive-green above, with a poorly marked yellowish supercilium, although this is more obvious in the Venezuelan races, especially those farthest from the main Andean chain. In a sense, it is well named; oleaginous—having the property or appearance of oil—is derived from olive, and this species is most certainly largely olive-colored. It is most liable to be confused with one of the smaller and finer-billed Basileuterus warblers, or the Superciliaried Hemispingus (Hemispingus superciliaris), which, as its name suggests, has a much more obvious supercilium. Its habits and behavior are typical of the genus as a whole.
14 cm; 14–20 g. Dingy, dull hemispingus with relatively slender bill. Nominate race has long, narrow, weakly indicated yellowish supercilium (most obvious in front of eye); crown and entire upperparts, including upperwing-coverts and tail, dull dirty olive, flight-feathers narrowly edged cinnamon; dingy olive-yellow below, more olive on sides, tinged cinnamon on undertail-coverts; iris dark brown; bill dusky grey; legs pale brownish to brownish-grey. Sexes similar. Juvenile lacks supercilium, is even duller and dingier than adult; immature like adult but duller. N races differ from nominate in generally brighter coloration: hanieli has brighter and more pronounced yellow supercilium, and is more yellow-ochre below; iterata differs from previous in having supercilium and throat tinged rich buff to orange-buff; ignobilis has greenish-yellow supercilium, with pale buffy throat better demarcated from breast than in other races; flavidorsalis has more olive upperparts, flight-feathers edged olive-green, and supercilium and throat with buff-yellow tinge.
Distribution and habitat
It is distributed by the coastal mountains of Venezuela, in the Serranía del Perijá and along the Andes, from the west of Venezuela, through Colombia, east of Ecuador, to the southeast of Peru (Cuzco). 
This species is considered uncommon in its natural habitat: the lower stratum of humid montane forests at altitude, mainly between 1500 and 2500 m. 
The species S. frontalis was first described by the Swiss ornithologist Johann Jakob von Tschudi in 1844 under the scientific name Hylophylus frontalis; the type locality is: «eastern slope of the Andes, Peru». 
The feminine generic name «Sphenopsis» is made up of the Greek words «sphēn»: wedge, and «opsis»: appearance; and the name of the species «frontalis» comes from modern Latin: from the front, from the eyebrows; in reference to the superciliary list characteristic of the species. 
The present species together with Sphenopsis melanotis (including S. ochracea and S. piurae), were traditionally included in the genus Hemispingus, until in 2010, publications of complete phylogenies of large sets of species of the Thraupidae family based on genetic sampling ,   made it possible to verify that they formed a separate clade from the genus they comprised, for which the resurrection of the genus Sphenopsis, until then considered a synonym of Hemispingus, was suggested.  The recognition of the resurrected genus and the inclusion of the two species was approved in Proposal No. 730.10 to the South American Classification Committee (SACC). 
According to the classifications of the International Ornithological Congress (IOC)  and Clements Checklist / eBird v.2019 , five subspecies are recognized, with their corresponding geographic distribution: 
Sphenopsis frontalis flavidorsalis (Phelps Sr & Phelps Jr), 1953 – Serranía del Perijá, border between Venezuela and Colombia.
Sphenopsis frontalis frontalis (Tschudi), 1844 – Subtropical Andes of eastern Colombia, eastern Ecuador, and eastern Peru.
Sphenopsis frontalis hanieli (Hellmayr & Seilern), 1914 – coastal mountains of northern Venezuela (Aragua to Miranda).
Sphenopsis frontalis ignobilis (P.L. Sclater), 1862 – Andes of western Venezuela (south of Lara, Trujillo, Mérida and Táchira).
Sphenopsis frontalis iterata (Chapman), 1925 – coastal mountains of northeastern Venezuela (Monagas to Sucre).
BirdLife International (2020). «Sphenopsis frontalis». IUCN Red List of Threatened Species 2020.2. ISSN 2307-8235. Retrieved January 29, 2021.
Tschudi, J. J. von (1844). «Avium conspectus quae in the Peruvian Republic reperiuntur et pleraeque observatae vel collectae sunt in itinere». Archiv für Naturgeschichte (in Latin). 10: 376 pp. + 8 tt. Pt1: 262-317. Berlin: Nicholai’schen Buchhandlung. Hylophilus frontalis, original description, p.284. Available at Biodiversitas Heritage Library. ISSN 0365-6136.
Burns, K.J., Unitt, P. & Mason, N.A. (2016). «A genus-level classification of the family Thraupidae (Class Aves: Order Passeriformes)» (Abstract). Zootaxa (4088): 329-354. ISSN 1175-5326. doi: 10.11646 / zootaxa.4088.3.2.
De Juana, E; Del Hoyo, J; Fernández-Cruz, M; Ferrer, X; Sáez-Royuela, R; Sargatal, J (2012). «Names in Spanish of the birds of the world recommended by the Spanish Ornithological Society (Sixteenth part: Order Passeriformes, Families Thraupidae to Icteridae)». Ardeola. Handbook of the Birds of the World (Madrid: SEO / BirdLife) 59 (1): 157-166. ISSN 0570-7358. Accessed December 9, 2014. P. 158.