Biology:Riocerida
| Riocerida | |
|---|---|
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | †Orthoceratoidea |
| Order: | †Riocerida King & Evans, 2019 |
| Families | |
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Riocerida,[1] originally named as Rioceratida,[2] 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).[1][2] 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).[2] 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.[1]
References
- ↑ 1.0 1.1 1.2 Pohle, Alexander; Kröger, Björn; Warnock, Rachel C. M.; King, Andy H.; Evans, David H.; Aubrechtová, Martina; Cichowolski, Marcela; Fang, Xiang et al. (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. PMID 35421982.
- ↑ 2.0 2.1 2.2 King, Andy H.; Evans, David H. (2019). "High-level classification of the nautiloid cephalopods: a proposal for the revision of the Treatise Part K" (in en). Swiss Journal of Palaeontology 138 (1): 65–85. doi:10.1007/s13358-019-00186-4. ISSN 1664-2384.
Wikidata ☰ Q112577892 entry
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