The investigation presented in this paper concerns the specific structuring of individual phonological systems, which is generally missing from research on feature classification and organization. More specifically, this paper examines the role of the features [continuancy] and [sonorant] in Spanish and argues that they are the driving forces of its phonological system. First, it shows that the interplay between both features result into four main natural classes with specific articulatory, acoustic and phonological characteristics. Second, it provides data that suggest that [continuancy] and [sonorant] interact in spirantization phenomena in various Spanish dialects. Third, building on proposals by Steriade (1993, 1994) and Clements and Hume (1995), this paper proposes an extended model of Aperture Theory where [continuant] and [sonorant] are associated to four different aperture degrees. The typology of aperture nodes (Amax, Ao, Af) is expanded via the addition of the partial aperture node Ap, which captures the group of nasals and laterals and permits the straightforward patterning of [sonorant] and [continuant] with four aperture degrees. This extended model captures the main natural classes of Spanish consonants and also the aerodynamically complex groups of laterals, rhotics and affricates. Additionally, it achieves a representational union between phonological and phonetic properties, expressed as features and aperture degrees respectively.