We provide a detailed description of the hyoid apparatus and cranial osteology of the gymnophthalmid lizard Neusticurus ecpleopus, based on a series of 11 dry skeletal preparations and 22 cleared and double-stained specimens. Articulated and disarticulated material permit detailed descriptions of isolated bones as well as the overall architecture of the skull. Individual and ontogenetic variation within N. ecpleopus is discussed. The greatest intraspecific variation is reflected in features that vary during ontogeny, including firmness of articulation between bones of the dermatocranium, thickness of individual bones, degree of elongation or expansion of processes, relative width of the parietal table, elongation of the hyoid apparatus, lateral angulation of the first ceratobranchial and relatively late appearance of the second ceratobranchial. The skull of N. ecpleopus can be regarded as generally representative of the Gymnophthalmidae, but we provide preliminary discussion of areas where variation in gymnophthalmid skull configuration is pronounced. (C) 2003 The Linnean Society of London.