Bassleroceratidae

Monogonoceras alabamense, from Furnish & Glenister (1964).

Belongs within: Cephalopoda.

The Lower Ordovician Bassleroceratidae were the earliest cephalopods to evolve an exogastrically curved shell. They may have been the ancestors of the later Tarphycerida and Oncocerida, and through the latter of the modern Nautilus.

Characteristics (from Furnish & Glenister 1964): Gradually expanded, smooth cyrtocones with slight to moderate exogastric curvature; conch strongly compressed to subcircular in section; siphuncle characteristically marginal and moderate in size, orthochoanitic.

<==Bassleroceratidae
    |--Anguloceras Unklesbay & Young 1956 FG64
    |    `--*A. ovatum Unklesbay & Young 1956 FG64
    |--Dwightoceras Ulrich & Foerste 1936 FG64
    |    `--*D. dactyloides (Dwight 1884) [=Cyrtoceras dactyloides] FG64
    |--Dyscritoceras Ulrich & Foerste 1936 FG64
    |    `--*D. metellus (Billings 1865) [=Cyrtoceras metellus] FG64
    |--Monogonoceras Ulrich, Foerste et al. 1944 FG64
    |    |--*M. alabamense Ulrich, Foerste et al. 1944 FG64
    |    |--M. magnisiphonatum Ulrich, Foerste et al. 1944 P68
    |    `--M. subrectum Ulrich, Foerste et al. 1944 P68
    |--Diaphoroceras Ulrich, Foerste et al. 1944 FG64
    |    |--*D. avaense Ulrich, Foerste et al. 1944 FG64
    |    |--D. belli FG64
    |    `--D. buffaloense Ulrich, Foerste et al. 1944 P68
    |--Bassleroceras Ulrich & Foerste 1936 FG64
    |    |--*B. perseus (Billings 1865) [=Orthoceras perseus] FG64
    |    |--B. bridgei Ulrich, Foerste et al. 1944 P68
    |    |--B. dalevillense Ulrich, Foerste et al. 1944 P68
    |    |--B. lasallense Ulrich, Foerste et al. 1944 P68
    |    `--B. tenuiculum Ulrich, Foerste et al. 1944 P68
    |--Lawrenceoceras Ulrich, Foerste et al. 1944 (see below for synonymy) FG64
    |    |--*L. collinsi Ulrich, Foerste et al. 1944 FG64
    |    |--‘Onychoceras’ australe Ulrich, Foerste et al. 1944 P68
    |    |--‘Onychoceras’ breve Ulrich, Foerste et al. 1944 P68
    |    |--L. confertissimum FG64
    |    `--‘Onychoceras’ subrotundum Ulrich, Foerste et al. 1944 P68
    `--Avaoceras Ulrich, Foerste et al. 1944 (see below for synonymy) FG64
         |--*A. elongatum Ulrich, Foerste et al. 1944 FG64
         |--‘Stylocyrtoceras’ avaense Ulrich, Foerste et al. 1944 P68
         |--‘Leptocyrtoceras’ curvatum Ulrich, Foerste et al. 1944 P68
         |--A. longidomum Ulrich, Foerste et al. 1944 P68
         |--A. magnisiphonatum Ulrich, Foerste et al. 1944 P68
         |--‘Leptocyrtoceras’ powellense Ulrich, Foerste et al. 1944 P68
         |--‘Leptocyrtoceras’ virginianum Ulrich, Foerste et al. 1944 P68
         `--A. wellsense Ulrich, Foerste et al. 1944 P68

Avaoceras Ulrich, Foerste et al. 1944 [incl. Leptocyrtoceras Ulrich, Foerste et al. 1944, Stylocyrtoceras Ulrich, Foerste et al. 1944] FG64

Lawrenceoceras Ulrich, Foerste et al. 1944 [=Lawrensoceras (l. c.); incl. Onychoceras Ulrich & Foerste 1936 non Wunstorf 1905] FG64

*Type species of generic name indicated

REFERENCES

[FG64] Furnish, W. M., & B. F. Glenister. 1964. Nautiloidea - Ellesmerocerida. In Treatise on Invertebrate Paleontology pt. K. Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea (R. C. Moore, ed.) pp. K129-K159. The Geological Society of America and the University of Kansas Press.

[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.