This subspecies is present in Sardinia, Corsica and North Africa. The life-cycle can be spent part in water, part on moist to dry soil. It grows in ponds and ephemeral pools that are flooded in winter and spring, but generally dry in the summer, usually on acidic substrates, from sea level to about 700 m. In Sardinia it occurs in the middle of the temporary ponds, where it forms dense, generally monospecific populations. The genus name derives from the Greek 'isos' (equal) and 'ethos' (year), in reference to the leaves that persist throughout the year; the species name refers to the macrosporangia, which are at least partially covered by a kind of veil; the name of the subspecies refers to Teulada, in northern Sardinia, the place from which the subspecies was originally described. Sporulation period: April to July.

Italian name(s): Calamaria dubbia (Italia), Calamaria tegulense (Italia), Isoete tegulense (Italia).