[2] E. kingii is one of the most common trilobite fossils in the USA[3] locally found in extremely high concentrations within the Wheeler Formation in the U.S. state of Utah.

E. kingii consistently occur in settings below the oxygen levels required by other contemporaneous epifaunal and infaunal benthic biota and may have derived energy from a food web that existed independently of phototrophic primary productivity.

Although other fossil organisms are known to have preferred such environments, E. kingii is the earliest-known inhabitant of them, extending the documented range of the exaerobic ecological strategy into the Cambrian Period.

"Even though the generic name Elrathia was first published in the combination E. kingii, a species from the House Range, Utah, the name, itself, is derived from Elrath, Cherokee County, Alabama.

In contrast, E. marjumi usually has 12 segments, 5 axial rings, lacks a notched posterior margin and possess incipient antero-lateral spines.