Cyrtogomphoceratidae

Cyrtogomphoceratidae Temporal range: M Ordovician - L Silurian
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Discosorida
Family:	Cyrtogomphoceratidae Flower & Kummel, 1950

The Cyrtogomphoceratidae is a family in the cephalopod order Discosorida that comprises genera commonly with compressed, endogastrically curved shells. Siphuncles lie close to the venral side, segments are broadly inflated, connecting rings thick and apically expanded thick bullettes. Chambers are short, separated by shallow, dish shaped septa. Apertures are generally simple.

The Cyrtogomphoceratidae are derived from the discosorid family Reudemannoceratidae, probably from Reudemannoceras, through the ancestral genus Ulrichoceras, and have a range from the Middle Ordovician to the Lower Silurian.

The family includes the following genera.

• Cyrtogomphoceras
• Kiaeroceras
• Konglungenoceras
• Landeroceras
• Parryoceras
• Strandoceras
• Ulrichoceras

Ulrichoceras is also considered the source for the exogastric Westooceratidae. The Cyrtogomphoceratidae, through Strandoceras, gave rise to the Silurian - L Devonian Phragmoceratidae which differ primarily in having thin connecting rings and variably modified, strongly contracted apertures.

References

• Flower, R H and Teichert, C; 1957. The Cephalopod Order Discosorida. University of Kansas Paleontological Contributions. Mollusca, Article 6, pp 1-144.
• Teicher, C. 1964. Nautiloidea-Discosorida. Treatise on Invertebrate Paleontology, Part K. Teichert and Moore, eds.