Acleistoceratidae

Ventral and lateral views of Amphicyrtoceras orcas, from Sweet (1964). The genus Amphicyrtoceras may represent the ancestral stock of other acleistoceratids.

Belongs within: Oncoceratidae.

The Acleistoceratidae were a Middle Silurian to Middle Devonian family of oncocerid cephalopods characterised by a broad siphuncle. Many species had a constricted triangular aperture.

Characters (from Sweet 1964): Depressed (rarely compressed, at least in early stages) exogastric brevicones and cyrtocones; siphuncle broadly expanded, actinosiphonate in some Devonian species.

<==Acleistoceratidae
    |--Acleistoceras Hyatt 1884 S64
    |    `--*A. olla (Saemann 1854) [=Apioceras olla] S64
    |--Austinoceras Foerste 1934 S64
    |    `--*A. turgidulum Foerste 1934 S64
    |--Clionyssiceras Foerste 1930 S64
    |    `--*C. petilum Foerste 1930 S64
    |--Crateroceras Foerste & Savage 1927 S64
    |    `--*C. raymondi Foerste & Savage 1927 S64
    |--Galtoceras Foerste 1934 S64
    |    `--*G. arcticameratum (Hall 1852) [=Cyrtoceras arcticameratum] S64
    |--Gonatocyrtoceras Foerste 1926 S64
    |    `--*G. heteroclytum (Barrande 1866) [=Cyrtoceras heteroclytum] S64
    |--Hercocyrtoceras Foerste 1927 S64
    |    `--*H. amator (Billings 1866) [=Oncoceras amator] S64
    |--Paracleistoceras Foerste 1926 S64
    |    `--*P. devonicans (Barrande 1865) [=Phragmoceras devonicans] S64
    |--Perioidanoceras Foerste 1930 S64
    |    `--*P. rotundatum Foerste 1930 S64
    |--Poteriocerina Foerste 1926 S64
    |    `--*P. lumbosum (Barrande 1877) [=Cyrtoceras lumbosum] S64
    |--Rhomboceras Foerste 1934 S64
    |    `--*R. welchi Foerste 1934 S64
    |--Slocomoceras Foerste 1930 S64
    |    `--*S. retrorsum Foerste 1930 S64
    |--Streptoceras Billings 1866 S64
    |    `--*S. janus Billings 1866 S64
    |--Anomeioceras Foerste 1930 S64
    |    |--*A. compressum Foerste 1930 S64
    |    `--A. brevicameratum Foerste 1930 P68
    |--Chadwickoceras Foerste 1930 S64
    |    |--*C. fusiforme Foerste 1930 S64
    |    `--C. erectum Foerste 1930 P68
    |--Grimsbyoceras Foerste 1934 S64
    |    |--*G. clitus (Billings 1866) [=Cyrtoceras clitus] S64
    |    `--G. hillsboroense Foerste 1934 P68
    |--Tumidoceras Flower 1949 S64
    |    |--*T. lentum Flower 1949 S64
    |    `--T. magnum Flower 1949 P68
    |--Byronoceras Foerste & Savage 1927 S64
    |    |--*B. longidomum Foerste & Savage 1927 S64
    |    |--B. commune Foerste 1930 P68
    |    `--B. transversale Foerste 1930 P68
    |--Ectocyrtoceras Foerste 1930 S64
    |    |--*E. marginatum Foerste 1930 S64
    |    |--E. gibberosum Foerste 1934 P68
    |    `--E. wilmingtonense Foerste 1934 P68
    |--Euryrizoceras Foerste 1930 S64
    |    |--*E. chadwicki Foerste 1930 S64
    |    |--E. anguloseptatum Foerste 1934 P68
    |    |--E. clinoseptatum Foerste 1934 P68
    |    |--E. percurvatum Foerste 1934 P68
    |    `--E. plenum Foerste 1930 P68
    |--Worthenoceras Foerste 1930 S64
    |    |--*W. elongatum Foerste 1930 S64
    |    |--W. byronense Foerste 1930 P68
    |    |--W. curtum Foerste 1930 P68
    |    |--W. exiguum Foerste 1930 P68
    |    `--W. subfusiforme Foerste 1934 P68
    `--Amphicyrtoceras Foerste 1924 S64
         |--*A. orcas (Hall 1862) [=Cyrtoceras orcas] S64
         |--A. bownockeri Foerste 1934 P68
         |--A. depressum Foerste 1930 P68
         |--A. inflatum Foerste 1930 P68
         |--A. laterale S64
         `--A. tantulum Foerste 1924 P68

*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 – Oncocerida. In Treatise on Invertebrate Paleontology pt. K. Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea (R. C. Moore, ed.) pp. K277-K319. The Geological Society of America and the University of Kansas Press.