Development of buccopharyngeal features in Thoropa miliaris (Spix, 1824) tadpoles (Anura: Cycloramphidae): Implications to character coding in systematics studies

Herein we present a survey on the variation in the morphology of the structures that compose the larval buccopharyngeal cavity of Thoropa miliaris tadpoles based on samples of 18 different stages of development, from embryos (removed from the egg capsules) to stages near or at metamorphosis. Our observations revealed that several structures vary independently along the stages. This variation appears in the number of (sub) unities, shape, and positions. Structures observed acquire a “mature format”, increase and decrease in size, and are reabsorbed during distinct tadpole stages. Our observations suggest that caution should be taken when assigning presence/absence or a specific morphology to characters derived from these structures and that samples of several semaphoronts (from as many different stages as feasible) should be evaluated prior to stating for instance that a structure is absent. We also discuss our findings regarding several interpretations of buccopharyngeal features of tadpoles and compare with the ontogenetic studies regarding this character system found in the literature.