Holonema

Holonema is thought to have been a benthic-dwelling fish, based on its cambered body shape, which performs better hydrodynamically when closer to the sea bed. Although previously thought to have fed in the bottom seafloor mud, more recent morphological studies of the jaw and toothplates suggest a more planktivorous lifestyle. Holonema fossil individuals have small stones in the trunk shield, and pieces of feldspar in the abdominal region, suggesting Holonema used these as gastroliths for processing food. ==Species==

H. rugosum H. rugosum is the type species. It was originally described as a species of the antiarch genus, Pterichthys. Fossils are found in Frasnian strata of New York and Pennsylvania, and Givetian strata of Wisconsin and Michigan. It is a fairly large species, though the type specimen is of an 18 centimeter long median dorsal plate belonging to a small individual. Fossils of H. horridum and Glyptaspis eastmani may be this species. Fossils from Frasnian Iran (H. cf. rugosum) may also belong to this species. H. arcticum A large species from Givetian-aged strata in Novaya Zemlya, Russia, known only from two plates from one individual's trunk shield. H. farrowi Known from fragments from the Givetian-aged "Traverse Group" stratum in Michigan. The median dorsal plates range up to 20 cm in length. The median dorsal plate is fairly broad at the posterior end, but narrows as one approaches the anterior end. == References ==