Osteocephalus pearsoni can be distinguished most readily from other members of the genus by the brown reticulate pattern on the venter, round brown spots on the flanks, and smooth skin on the flanks. Also, it is the least tuberculate species in the genus.
Distribution.—Upper Amazon Basin and Amazonian slopes of the Andes in central Perú (1620 m in Río Ucayali drainage) and northern Bolivia (less than 500 m in Río Beni drainage) ([Fig. 8]). 6 specimens from 3 localities.
Remarks.—The specimen from Yaupi, Perú (KU 136312) is a subadult female having a snout-vent length of 39.8 mm. In life the coloration was: "Dorsum light pinkish brown with large rich chocolate brown blotch from eyes to anterior tips of ilia; numerous small chocolate blotches on flanks; dorsal surfaces of thighs and shanks, canthus, and supraorbital region to insertion of forearm chocolate brown; supralabial border and short bar from eye to lip bronze-white; venter bronze-white with numerous tiny chocolate brown flecks [tending to form reticulations on throat and chest]; anterior and posterior surfaces of thighs light olive-brown; iris largely black with gold flecks." (Thomas H. Fritts, field notes, 23 March 1970.) On the basis of this one subadult, it seems likely that reticulations on the venter develop with age.
Osteocephalus taurinus Steindachner
Osteocephalus taurinus Steindachner, 1862:77 [Holotype.—NHMW 16492 from Barra do Río Negro, Manáus, Territorio do Amazonas, Brasil; Johann Natterer collector].
Osteocephalus flavolineatus Steindachner, 1862:80 [Holotype.—NHMW 16495 from Cucuí, Territorio do Amazonas, Brasil; Johann Natterer collector].
Trachycephalus (Osteocephalus) taurinus Steindachner, 1867:64.
Osteocephalus planiceps Cope. 1874:122 [Holotype.—ANSP 11399 from Nauta, Departamento de Loreto, Perú; James Orton collector]. New synonymy.
Hyla taurina—Boulenger, 1882:363 [synonymized Osteocephalus flavolineatus Steindachner, 1862, with O. taurinus Steindachner, 1862].
Hyla planiceps—Boulenger, 1882:364.