PaleoDB taxon number: 609
Original description: Test multicyrtid, spindle-shaped (conical when broken), with or without constrictions between joints. Cephalis dome-shaped with horn. Earlier chambers covered with layer of microgranular silica, remaining chambers consisting of single layer of regular to subregular polygonal pore frames. Final post-abdominal chambers slightly inflated and terminating in open, narrow, elongate, tubular extension.
Original remarks: Pleesus, n. gen., differs from Katroma Pessagno and Poisson (1981) by lacking a horn on cephalis, and by having a less inflated final post-abdominal chamber.
Etymology: Pleesus is a name formed by and arbitrary combination of letters (ICZN, 1985, Appendix D, pt. VI, Recommndation 41, p. 201).
Full reference: K. Y. Yeh. 1987. Taxonomic Studies of Lower Jurassic Radiolaria from East-Central Oregon. National Museum of Natural Science Special Publications 2:1-169
Subtaxa: Pleesus aptus
Ecology: passively mobile planktonic omnivore