The Cyrtogomphoceratidae are a family in the cephalopod order
Discosorida
Discosorida are an order of cephalopods that lived from the beginning of the Middle Ordovician, through the Silurian, and into the Devonian. Discosorids are unique in the structure and formation of the siphuncle, the tube that runs through and co ...
that comprises genera commonly with compressed, endogastrically curved shells. Siphuncles lie close to the ventral 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
[Teicher, C. 1964. Nautiloidea-Discosorida. Treatise on Invertebrate Paleontology, Part K. Teichert and Moore, eds.] includes:
:*''
Cyrtogomphoceras''
:*''
Kiaeroceras
''Kiaeroceras'' is a slender, nearly straight shelled, cyrogomphoceratid (Nautiloidea-Discosorida
Discosorida are an order of cephalopods that lived from the beginning of the Middle Ordovician, through the Silurian, and into the Devonian. Dis ...
''
:*''
Konglungenoceras''
:*''
Landeroceras''
:*''
Parryoceras''
:*''
Strandoceras''
:*''
Ulrichoceras''
''Ulrichoceras'' is also considered the source for the exogastric
Westonoceratidae
Westonoceratidae are exogastric, mostly compressed, Discosorida of moderate size from the Middle Ordovician to the Lower Silurian.
The siphuncle is typically close to the convexly curved outer margin of the phragmocone – the chambered part of ...
. 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
{{Taxonbar, from=Q5201020
Prehistoric nautiloid families
Middle Ordovician first appearances
Silurian extinctions
Discosorida