USA. Georgia, McIntosh Co., Sapelo Island, Sapelo Island Wildlife Management Area, 31°26'00"N, 81°22'10"W, on bark of Quercus, 16 December 2009, J. Lendemer 20995 (holotype: NY).

Similar to Neoprotoparmeliabrasilisidiata, but differing by the thicker, 0.07–0.11 mm wide, isidia.

Named after its distribution in North America and the presence of isidia.

Thallus up to ca. 0.05 mm thick, shiny, pale olive-green to olive-grey, continuous, delimiting marginal prothallus line (brown, thin or absent). Isidia always numerous, initially widely dispersed or somewhat clustered, eventually covering much of the thallus, up to 1.5 mm long, persistently 0.07–0.11 mm wide over their whole length, cylindrical, usually irregularly repeatedly branched and somewhat nodulose, glossy, pale olive-green to olive-grey, tips distinctly brown and dull. Apothecia and pycnidia not observed.

Spot tests: medulla of thallus and isidia UV++ greenish-white, C–, P–, K–, KC+ pink. TLC: alectoronic acid (major), dehydroalectoronic acid (minor or trace) and β-alectoronic acid (trace).

On tree bark in forest. Known only from the south-eastern USA (North Carolina, Alabama, Georgia, Mississippi and Florida).

(specimen: Lendemer 20995, holotype: NY). KY012827 (mtSSU), KY066301(nuLSU).

This species comprises the specimens recovered within ‘P.isidiata A’ in ‘Protoparmelia tropical clade’ in Singh et al. (2015). It is morphologically most similar to N.brasilisidiata which only differs by the generally thinner isidia. Some specimens have been reported before as Protoparmeliaisidiata (Lendemer and Lumbsch 2008).

USA. Florida, Gilchrist Co., Waccasassa Flats, 5 December 1993, R.C. Harris 31685, 31755 (NY), R.C. Harris 31685 (NY); USA. Georgia, McIntosh Co., Sapelo Island, Sapelo Island Wildlife Management Area, 15 December 2009, J. Lendemer 20745, 20727 (NY).