Abstract
A novel kind of small scale structures in diffuse molecular clouds comes to light as the locus of the extrema of velocity shears in CO line maps. These extrema build up the non-Gaussian tails of the probability distribution functions (PDFs) of line centroid increments measured at small lags. They form elongated structures of variable thickness, often unresolved in their transverse dimension. They are essentially pure velocity structures and may trace locations of enhanced dissipation in interstellar turbulence. This interpretation is corroborated by the large HCOp abundance observed in one of such structures and the discovery of a small fraction of warm HH within the cold interstellar medium, emitting pure rotational lines which cannot be accounted for by UV pumping.