Holonematidae

Holonematidae Temporal range: ?Emsian to Frasnian
Holonema rugosum
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Placodermi
Order:	Arthrodira
Family:	Holonematidae
Type species
"Pterichthys rugosum" Claypole, 1883
Genera
Artesonema Lelièvre & Goujet, 1986 Belemnacanthus Eastman, 1898 Bimbianga Young, 2005 Deirosteus Wells, 1942 Deveonema Kulczycki, 1957 Gyroplacosteus Obruchev, 1932 Holonema Newberry, 1889 Rhenonema Obruchev, 1964 Tropidosteus Gross, 1933

Holonematidae is an extinct family of relatively large arthrodire placoderms from the Early to Late Devonian. 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. The trunkshield is very elongated, giving the armor an overall "barrel" like appearance.

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.