Almost all fossil specimens are of armor fragments, though, all have distinctive ornamentation, often of unique arrangements and patterns of tubercles, that are diagnostic of the family.

Due to pebbles found inside articulated specimens of the Frasnian species, Holonema westolli, holonematids are thought to have been specialized herbivores that grazed on a form of horn-shaped, stony algae called "onycholite," snipping off the tips with their odd snouts.

The genus is known only from the holotype: a 37 cm long portion of a median dorsal plate, suggesting a very large animal.

[3] If Bimbianga is a holonematid, then it is the earliest genus, dating from the Emsian-aged Taemas Limestone of Wee Jasper, New South Wales.

Bimianga's placement within Holonematidae is questionable, as the morphology of its plates and ornamentation are very similar to those of the arthrodire incertae sedis Aspidichthys.

Holonema is also the most widespread genus, as the various species are found in Eifelian to Frasnian-aged deposits in the United States, Scotland, Europe, Western Asia, and Australia.