Geisonoceratidae

Cross-section and lateral view of Virgoceras palemon, from Sweet (1964).

Belongs within: Michelinoceratida.

The Geisonoceratidae were a Middle Ordovician to Middle Devonian family of orthocerid cephalopods distinguished by their siphucular structure.

Characters (from Sweet 1964): Orthoconic or cyrtoconic conchs with subcircular cross-section; orthochoanitic to suborthochoanitic siphuncle occupied by endosiphuncular annuli restricted to septal foramen or growing anteriorly against connecting rings; endosiphuncular annuli in advanced species fusing with those of adjacent segments to form continuous siphuncular lining.

<==Geisonoceratidae
    |--Columenoceras Barskov 1960 S64
    |    `--*C. columen (Barrande 1874) [=Orthoceras columen] S64
    |--Harrisoceras Flower 1939 S64
    |    `--*H. orthoceroides Flower 1939 S64
    |--Joachimoceras Barskov 1960 S64
    |    `--*J. micromegas (Barrande 1874) [=Orthoceras micromegas] S64
    |--Jonesoceras Barskov 1960 S64
    |    `--*J. jonesi (Barrande 1874) [=Orthoceras jonesi] S64
    |--Mesnaquaceras Flower 1955 S64
    |    `--*M. curviseptatum Flower 1955 S64
    |--Temperoceras Barskov 1960 S64
    |    `--*T. temperans (Barrande 1874) [=Orthoceras temperans] S64
    |--Virgoceras Flower 1939 S64
    |    `--*V. palemon (Barrande 1870) [=Orthoceras palemon] S64
    |--Geisonocerina Foerste 1935 S64
    |    |--*G. wauwatosense (Whitfield 1882) [=Orthoceras wauwatosense] S64
    |    `--G. landerensis Foerste 1935 P68
    |--Protokionoceras Grabau & Shimer 1910 S64
    |    |--*P. medullare (Hall 1868) [=Orthoceras medullare] S64
    |    |--P. oneidaense P68
    |    `--P. perstrigatum Foerste 1936 P68
    |--Striacoceras Flower 1936 S64
    |    `--*S. typum (Saemann 1854) [=Orthoceras typum] S64
    |         |--S. t. typum S64
    |         `--S. t. beta S64
    `--Geisonoceras Hyatt 1884 S64
         |--*G. rivale (Barrande 1866) [=Orthoceras rivale] S64
         |--G. bipellis T64
         |--G. clavatum T64
         |--G. rochesterense Foerste 1928 P68
         |--G. scabridum S64
         `--G. teicherti T64

*Type species of generic name indicated

REFERENCES

[P68] Purnell, L. R. 1968. Catalog of the Type Specimens of Invertebrate Fossils. Part I: Paleozoic Cephalopoda. United States National Museum Bulletin 262: 1-198.

[S64] Sweet, W. C. 1964. Nautiloidea – Orthocerida. In Treatise on Invertebrate Paleontology pt. K. Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea (R. C. Moore, ed.) pp. K216-K261. The Geological Society of America and the University of Kansas Press.

[T64] Teichert, C. 1964. Morphology of hard parts. In Treatise on Invertebrate Paleontology pt. K. Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea (R. C. Moore, ed.) pp. K13-K53. The Geological Society of America and the University of Kansas Press.