Technically ranked as a "section" grade, but ranking as subfamily because below family rank.
Full reference: O. M. B. Bulman. 1970. Graptolithina with sections on Enteropneusta and Pterobranchia (Second edition, revised and enlarged). Treatise on Invertebrate Paleontology V:V1-V163
Ecology: passively mobile planktonic suspension feeder
Total: 8 collections each including a single occurrence