The insects and plants suggest a climate similar to modern Southeastern North America, with a number of taxa represented that are now found in the subtropics to tropics and confined to the Old World.

[3][4][5] At the time of description the holotype specimen, number 3976 was deposited in the Museum of Comparative Zoology paleontology collections at Harvard University.

Placement of the group has changed several times, with Nepherocerus Metanephrocerus Priabona and Protonephrocerus being placed in the pipunculid subfamily Nephrocerinae from 1948 until 2014.

The placement of the tribe Protonephrocerini, containing Metanephrocerus and Protonephrocerus, was challenged in 2014 by Kehlmaier, Dierick and Skevington who suggested inclusion of the genera made Nephrocerinae paraphyletic.

The femurs of P. florissantius are unique in that they have several darkened spines on the undersides and which have setae on the front and upper sides, a feature absent in Nephrocerus.