Abstract
In numerous IE languages, either their synchronic fact or the diachronic processes reveal some level of asymmetry in the area of coronal obstruents, specifically the stops and the nasal, or their reflexes resulting from various phonetic processes as assibilation, palatalization, or lenition. Especially the evidence from Germanic, Greek, Italic, Tocharian, and Anatolian supports the hypothesis that such a symmetry is a shared and possibly inherited feature of their phonology.
Data from Indic and Armenian may also provide further support, while the merger of the voiced stops and voiced aspirated stops in Iranian, Balto-Slavic, Albanian and Celtic make their evidence less reliable. Overall, the evidence points toward the reflexes of PIE *d patterning with PIE *n, while the reflexes of *dh and *t often result in markedly different outcomes of the same individual changes which also at the same stage target *d.
The apical character of *d is the best explanation of the frequent shift towards, on the one hand, rhotics and laterals, on the other, to sibilants realized at a different articulatory position than that of the other members of the same dental-alveolar series.