A. Posterior outer toe longer than the anterior outer one. (Fourth toe longer than third.)
a. Lateral ridge starting above the middle of the base of the bill, and extending to the tip.
1. Campephilus. Lateral ridge above the middle of the lateral profile of the bill when opposite the end of the nostrils, which are ovate, and rounded anteriorly. Bill much depressed, very long; gonys very long. Posterior outer toe considerably longer than the anterior. Primaries long, attenuated towards the tip. Spurious quill nearly half the second. Shafts of four middle tail-feathers remarkably stout, of equal size, and abruptly very much larger than the others; two middle tail-feathers narrower towards bases than towards end.[125] A pointed occipital crest.
2. Picus. Lateral ridge in the middle of the lateral profile opposite the end of the nostrils, which are ovate and sharp-pointed anteriorly. Bill moderate, nearly as broad as high.
Outer hind toe moderately longer than the outer fore toe. Primaries broad to the tip, and rounded. Spurious primary not one third the second quill.
3. Picoides. Lateral ridge below the middle of the profile, opposite the end of the ovate acute nostrils, which it greatly overhangs. Bill greatly depressed; lower mandible deeper than the upper. Inner hind toe wanting, leaving only three toes. Tufts of nasal bristles very full and long.
b. Lateral ridge starting below the middle of the base of the bill, and running as a distinct ridge into the edge of the commissure at about its middle; the terminal half of the mandible rounded on the sides, although the truncate tip is distinctly bevelled laterally.
4. Sphyropicus. Nostrils considerably overhung by the lateral ridge, very small, linear. Gonys as long as the culmen, from the nostrils. Tips of tail-feathers elongated and linear, not cuneate. Wings very long; exposed portion of spurious primary about one fourth that of second quill.
B. Posterior outer toe considerably shorter than the anterior outer one. (Fourth toe shorter than third).
5. Hylotomus. Bill depressed. Lateral ridge above the middle of the lateral profile near the base. Nostrils elliptical, wide, and rounded anteriorly. Tail almost as in Sphyropicus. A pointed occipital crest, as in Campephilus, and not found in the other genera.