The wiegmannii group of Liolaemus includes L. lutzae, L. occipitalis, L, multimaculatus, L. rabinoi, L. riojanus, L. salinicola, L. scapularis, and L. wiegmannii; the status of L. cranwelli is uncertain, but is here considered a synonym of L, wiegmannii. The morphological characteristics of the wiegmannii group as a whole are described, and a taxonomic review, together with descriptions, distributions, and natural histories are presented for each species. This study then investigates the sequence of morphological changes that accompanied the evolution of the wieg-mannii group. Seven of these, referred to here as the "sand-lizards" are confined to a substrate of loose, aeolean sand with extensive open dunes or sand flats. All of these species are members of a more inclusive clade, the boulengeri group. A phylogenetic analysis of the boulengeri group, based on 39 morphological and one behavioral character, produced a single most parsimonious tree that included the wiegmannii group as a fully resolved clade. This clade has a pectinate topology, with the following relationships: wiegmannii (lutzae (salinicola (scapularis (occipitalis (multimaculatus (riojanus + rabinoi)))))), with sand lizards represented by the last seven species, i.e., L. wiegmannii, is the sister taxon to the sand lizards. Many of the morphological and behavioral transformations that occur at the origin of, and subsequently within the sand lizards, facilitate life on and under the surface of loose, wind-blown sand. Rapid diving and burial under the sand may be facilitated by a wedge-shaped snout with numerous small scales on the dorsal and lateral surfaces of the head, a sharp keel formed by the scales of the lower jaw, and a serrate margin on the shoulders and edges of the tail. Breathing under sand by vertical movement of the sternum may be facilitated by a wider sternum, with the fontanel reduced or absent, and a short median interclavicle process. A, small ear opening, projecting ciliary scales, and a partly countersunk lower jaw should help to exclude sand from body openings. Fringes of projecting scales on the toes, and smooth, non-imbricate scales on the palms and soles should facilitate surface locomotion on sand. Reduction in dorsal sexual dicromatism, and close substrate color and pattern matching render them cryptic on the sand. Burial as a means of nocturnal retreat occurs in the sand lizards and most other species of the boulengeri group, but rapid diurnal burial as a means of escape occurs only in L. wiegmannii and the sand lizards.
