Misplaced Pages

Dissidocerida Temporal range: Lower Ordovician - Lower Silurian
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	†Orthoceratoidea
Order:	†Dissidocerida Zhuravleva (1994)
Families
See text

Dissidocerida is an order of Early Ordovician to the Early Silurian orthoceratoid cephalopods in which the siphuncle has a continuous lining or a longitudinal rod-like structure within.

The order Dissidocerida was proposed by Zhuravleva (1994) for Dissidoceras undosum Zhuravleva, 1964, a Silurian orthoconic genus with a wide, nearly central, tubular siphuncle, suborthochoanitic septal necks, and endosiphuncular rod; in many aspects similar to rod-bearing orthocones of the Ordovician. It is thought by some that Ordovician-Silurian orthocones with continuous longitudinal endosiphuncular laminar deposits constitute a single phylogenetic stock.

The Dissidocerida as understood includes the Polymeridae, Rangeroceratidae, Troedssonellidae, and Dissidocertidae. The Polymeridae and Rangeroceratidae were proposed by Evans in 2005 for Polymeres Murchison 1839 and Rangeroceras Hook and Flower 1977, respectively. Troedssonellidae was established by Kobayashi in 1935 and is based on the genus Troedssonella. The Dissidoceratidae was established by Zhuravleva for Dissidoceras undosum

References

• A. A. Shevyrev 2004, The Cephalopod Macrosystem: A Historical Review, the Present State of Knowledge, and Unsolved Problems: 2. Classification of Nautiloid Cephalopods.
• Bjorn Kroger, 2008. A new genus of middle Tremadocian orthoceratoids and the Early Ordovician origin of orthoceratoid cephalopods. Brief Report Acta Palaeontologica Polonica 53 (4): 745–749
• Paleobiology -Dissidocerida

v t e Notable fossil cephalopods (listed by first occurrence)
Cenozoic	The belemnite-cuttlefish-like Belosaepia	Evolution of cephalopods
Mesozoic	Advanced nautiloids Nautilaceae True ammonites Early coleoids Muensterelloidea Proteroctopus Styletoctopus Keuppia Palaeoctopus Paleocirroteuthis Vampyronassa Ceratitid ammonoids late Nautilida Advanced belemnoids Diplobelids: Diplobelus Belemnites: Belemnites Belemnopsis Belemnotheutis
Palaeozoic	Earliest unambiguous cephalopods: Plectronocerida: Plectronoceras, Monoplacophora-like form: Knightoconus? First appearance of long-lasting lineages Goniatite and ceratite ammonoids Probable coleoid ancestor Bactritida Early coleoids: Jeletzkya?, Gordoniconus, Syllipsimopodi Earliest belemnoids: Aulacocerids Phragmoteuthids Early forms the earliest cephalopod group Ellesmerocerida Orthocones: Endocerida, Orthocerida, Actinocerida Brevicones: Ascocerida, Oncocerida Earliest coiled cephalopods: Tarphycerida Spirulid?: Shimanskya
Misidentified	Probable misidentified genera Nectocarididae: (Nectocaris, Nectocotis) Kirengellida Volborthella Shelbyoceras Pohlsepia

• Orthoceratoidea
• Prehistoric cephalopod orders
• Ordovician cephalopods
• Silurian cephalopods
• Ordovician first appearances
• Silurian extinctions