Temporal range: Silurian-Permian
Hederellids are extinct colonial animals with calcitic tubular branching exoskeletons. They range from the Silurian to the Permian and were most common in the Devonian period. They are more properly known as "hederelloids" because they were originally defined as a suborder by Bassler (1939), who described about 130 species. Although they have traditionally been considered bryozoans, they are clearly not because of their branching patterns, lack of an astogenetic gradient, skeletal microstructure, and wide range in tube diameters (Wilson and Taylor, 2001). Work continues on assessing the true affinities of hederelloids, but they appear to be most closely related to phoronids and other lophophorates (Taylor and Wilson, 2008; Taylor et al., 2010).
Three hederelloid species on a Devonian rugose coral
Hederelloids encrusting a brachiopod from the Devonian of Ohio
SEM image of a hederelloid from the Devonian of Michigan (largest tube diameter is 0.75 mm)