Fossils of Nanahughmilleria have been discovered in deposits of Devonian and Silurian age in the United States, Norway, Russia, England and Scotland, and have been referred to several different species.

The largest species confidently assigned to the genus was N. norvegica at 10 cm (3.9 in), making it a comparatively small eurypterid.

[1] Nanahughmilleria had long and narrow reniform (bean-shaped) eyes placed in an intramarginal (occurring within the margin) position.

[5] Nanahughmilleria is only distinguished from the more derived members of Adelophthalmidae in the shorter and smaller spatulae and in the increased spinosity in the appendages.

[3] In 1884, James Hall described another species of Eurypterus, E. prominens, based on a single carapace from the Clinton Group, a geological formation of the United States.

[2] In fact, notes left by Kjellesvig-Waering in museum drawers indicate that he wanted to erect a new genus for N. prominens, Clintonipterus.

Its operculum (a plate-like segment which contains the genital aperture) had a long, narrow spatulae (compared to most eurypterids).

[3] N. norvegica was the largest species of Nanahughmilleria, measuring 10 cm (3.9 in, with the exception of N. lanceolata, which may represent a separate genus).

[2] In 1957, L. P. Pirozhnikov described two new species of eurypterids, N. schiraensis and Parahughmilleria matarakensis, and erroneously assigned them to the stylonurine genus Rhenopterus.

[8] Kjellesvig-Waering and Willard P. Leutze noticed that the species did not really represent a Rhenopterus and they assigned it in 1966 to its current genus.

[9] It has been suggested that this species is a synonym of P. matarakensis,[2] but the Russian paleontologist Evgeniy S. Shpinev does not agree with this since the prosoma of N. schiraensis was longer and its eyes were closer to the margin than in P.

[11] N. clarkei is based on a series of fossils described and assigned to Hughmilleria shawangunk by John Mason Clarke and Rudolf Ruedemann in 1912.

Kjellesvig-Waering realized this and erected the species N. clarkei in 1964, named after Clarke, who described the original Shawangunk eurypterid fauna.

Its specific name, notosibirica, comes from the Greek word notos (southern) and Siberia, referring to the place where it was discovered.

[2] In 2004, O. Erik Tetlie erected the family Nanahughmilleridae in a thesis to contain the adelophthalmoids with no or reduced genital spatulae and the second to fifth pair of prosomal appendages of Hughmilleria-type.

[15] The cladogram below presents the inferred phylogenetic positions of most of the genera included in the three most derived superfamilies of the Eurypterina suborder of eurypterids (Adelophthalmoidea, Pterygotioidea and the waeringopteroids), as inferred by O. Erik Tetlie and Markus Poschmann in 2008, based on the results of a 2008 analysis specifically pertaining to the Adelophthalmoidea and a preceding 2004 analysis.

[2] Orcanopterus Waeringopterus Grossopterus Eysyslopterus Bassipterus Pittsfordipterus Nanahughmilleria Parahughmilleria Adelophthalmus Hughmilleria Herefordopterus Slimonia Erettopterus Pterygotus Acutiramus Jaekelopterus Fossils of Nanahughmilleria have been found from the Silurian deposits of the Llandovery epoch to the Devonian deposits of the Eifelian epoch in North America, Europe and Siberia.

[17] In addition, the streamlined shape of the body of Nanahughmilleria suggests that it was an active swimmer capable of swimming against currents.

The Silurian deposits of Ringerike, Norway, where fossils of N. norvegica have been discovered, include fossil remains of Mixopterus kiaeri, Stylonuroides dolichopteroides, Kiaeropterus ruedemanni and Erettopterus holmi, among other organisms like the malacostracan Dictyocaris slimoni or the chasmataspidid Kiaeria limuloides.

[18] On the other hand, Nanahughmilleria schiraensis and Parahughmilleria matakarensis are the only animals of the Devonian deposits of Khakassia, Russia, together with land plants.