The earliest genus included in the Nephriticeraatidae is the sinistrally torticconic
Sphyradoceras, which comes from the Lower Devonian Schoharie Formation of New York. It is in fact the only torticonic genus in the family and the only genus known from the Barrandeocerina from the Lower Devonian. The early stage of
Sphyradoceras is gyroconic, coiled in a plane but with whorls not touching, resembling the adult stage of the
barrandeoceratid genus
Bickmorites. This might suggest that the Nephriticeratidae has its origin in the Barrandeoceratidae, from
Bickmorites, however the latest
Bickmorites are from the Middle Silurian, leaving a gap in the Upper Silurian with no intermediary forms. There is a genus form the Upper Silurian,
Peismoceras which is included in the
Lechritrochoceratidae, the only barradeocerin from that epoch, which could be ancestral, without having to account for any significant temporal gap. The problem is that
Peismoceras is coiled dextrally, right handedly. ==Genera==