The holotype of
E. primordialis is the uncrushed and mostly intact anterior half of an individual with the articulating head and trunk armor preserved in three dimensions. The holotype is about long, and the live animal is estimated to have been over long. In overall form, the animal resembles primitive
arthrodires, but the anatomy of the jaws strongly suggests the anatomies of
bony fish and
tetrapods. Specifically, this is the first stem gnathostome with dermal marginal jaw bones. These bones are the
premaxilla,
maxilla, and
dentary. The researchers' cladistic diagram suggests that
E. primordialis forms a
polytomy with arthrodires,
ptyctodonts, and all advanced
gnathostomes (namely bony fish, tetrapods,
acanthodians, and chondrichthyes). ==Etymology==