PBDB Taxon

Basic info	Taxonomic history	Classification	Included Taxa
Morphology	Ecology and taphonomy	External Literature Search	Age range and collections

Cyrtoceras minneapolis

Cephalopoda - Oncocerida

Taxonomy

Cyrtoceras minneapolis was named by Clarke (1897). It is the type species of Cyrtorizoceras.

It was recombined as Cyrtorizoceras minneapolis by Hyatt (1900), Teichert (1930).

Sister species lacking formal opinion data

C. hospitale, C. kirkbyi, C. eatonense

Year	Name and author
1897	Cyrtoceras minneapolis Clarke p. 808 figs. Pl. LIX, Figs 1-8.
1900	Cyrtorizoceras minneapolis Hyatt p. 529
1930	Cyrtorizoceras minneapolis Teichert p. 290

Diagnosis

Reference	Diagnosis
J.M. Clarke 1897	Shell arcuate, rapidly expanding to the aperture. Body-chamber without constriction; apical curvature not known. Surface laterally compressed; sides broad; dorsum narrow, venter still narrower and more arcuate. Transverse section subelliptical, the major and minor diameters being as 11 to 9 at the next to the last septum, and as 16 to 11 at the aperture. The lateral margins of the aperture are convex, the dorsal and ventral margins broadly and narrowly concave or re-entrant, respectively. The septa are regularly and evenly, though not deeply concave, the deepest concavity being at about the center. The sutures are transver::;e and simple, without lobes or saddles save for a slight upward inclination on the venter, which gives to the air-chambers a greater depth on the ventral than on the dorsal side. Sipho ventral, submarginal, expanded in each air-chamber. Surface covered with closely crowded concentric lines, conforming in curvature to the aperture. On the internal cast are traces of longitudinal ridges over the body-chamber. A small and typical example has the aperture 16 mm. in major, and 11 mm. in minor diameter. At the next septum to the last these dimensions are 11 and 9 mm. In a large specimen the aperture is 21.5x15 mm. and at the third septum from the aperture 15x12 mm. This species has some similarity to Cyrtoceras camurum
A. Hyatt 1900	Sections more compressed than in Rizoceras, living chamber shorter and apt to be more or less laterally compressed in gerontic stage, but the dorso-ventral diameters only very slightly so or not at all. Sutures more sinuous, and with decided ventral and dorsal saddles.
C. Teichert 1930	"Querschnitt mehr seitlich zusammengedriickt als bei Rizoceras, Wobnkammer kiirzer uud neigt dazu, im Altersstadiummehr odeI' weniger seitlich zusammengedriicktder dorsoventrale Durchmesser nur sehr gering oder iiberhaupt Suturen mehr gebogen und mit betonten Dorsal-und Ventral zu werden, wahrend nicht verengert wird satteln,