Troedssonellidae is a family of
orthoceroid cephalopods from the
Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya.
T ...
, derived from rod-bearing
Baltoceratidae
Baltoceratidae is an extinct family of orthoconic cephalopods belonging to the subclass Nautiloidea endemic to what would be Asia, Australia, Europe, North America, and South America during the Ordovician living from about 480–460 mya, exi ...
, that have a continuous lining within the
siphuncle that resembles very thin and slender endocones. Shells are generally slender and orthoconic. The siphuncle is central or subcentral, composed of straight or slightly expanded segments. Septal necks generally short and connecting rings are thin. Thin cameral deposits (lining the chambers) are known, which along with the position of the siphuncle and thin connecting rings distinguishes them from the
endocerids in which they have been included.
[Flower 1976. Ordovician Cephalopod Faunas and Their Role in Correlation, in The Ordovician System: proceedings of a Palaeontological Association symposium, Sept 1974]
Troedsonnellids first appear high in Lower Ordovician (
Cassinian The Cassinian is the latest age of the Canadian Epoch when thought of temporally and the uppermost stage of the Canadian Series when thought of stratigraphically. The Canadian, either as a series or as an Epoch is the name that has been given to t ...
) strata, beginning with ''
Tajaroceras'' and extend at least through the
Whiterock Stage
The Whiterockian, often referred to simply as the Whiterock, is an earliest or lowermost stage of the Middle Ordovician. Although the Whiterockian or Whiterock Stage refers mainly to the early Middle Ordovician in North America, it is often used in ...
of the Middle Ordovician.
[Hook and Flower 1977. Late Canadian (Zones J,K) Cephalopod Faunas from Southwestern United States: Memoir 32, New Mexico Bureau of Mines and Mineral Resources.] They also may have given rise to the Striatoceratidae and to the Narthecoceratidae of the Middle and Late Ordovician.[
=Genera=
*'' Tajaroceras''
*'' Buttsoceras''
*'' Oxfordoceras''
*'' Ctenoceras''
*'' Troedsonnella''
Genera of dubious placement:
*'' Glenisteroceras''
*'' Wolungoceras''
]
References
{{Taxonbar, from=Q7844939
Orthoceratoidea