Misplaced Pages

Riocerida

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
Extinct order of nautiloids

Riocerida
Temporal range: Tremadocian–Katian PreꞒ O S D C P T J K Pg N
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Orthoceratoidea
Order: Riocerida
King & Evans, 2019
Families

Riocerida, originally named as Rioceratida, is an extinct order of Ordovician nautiloid cephalopods. They were the earliest-diverging members of the major group Orthoceratoidea, with which they share dorsomyarian muscle scars (a few large muscle scars concentrated at the top of the body chamber). However, they also possess several plesiomorphic ("primitive") traits which are absent in other orthoceratoids: Cameral and endosiphuncular deposits are absent, and the siphuncle has a marginal position along the lower edge of the shell. The conch (external shell) shape is slender, usually orthoconic (straight) or weakly cyrtoconic (slightly curved). The monophyly of Riocerida as a unique group is plausible but difficult to confirm, and they may instead be a paraphyletic grade or polyphyletic assemblage ancestral to all later orthoceratoids.

References

  1. ^ Pohle, Alexander; Kröger, Björn; Warnock, Rachel C. M.; King, Andy H.; Evans, David H.; Aubrechtová, Martina; Cichowolski, Marcela; Fang, Xiang; Klug, Christian (2022-04-14). "Early cephalopod evolution clarified through Bayesian phylogenetic inference". BMC Biology. 20 (1): 88. doi:10.1186/s12915-022-01284-5. ISSN 1741-7007. PMC 9008929. PMID 35421982.
  2. ^ King, Andy H.; Evans, David H. (2019). "High-level classification of the nautiloid cephalopods: a proposal for the revision of the Treatise Part K". Swiss Journal of Palaeontology. 138 (1): 65–85. Bibcode:2019SwJP..138...65K. doi:10.1007/s13358-019-00186-4. ISSN 1664-2384. S2CID 133647555.
Categories: