Talk:Neocephalopoda

comments

A well written and organized article overall, thanks primarily to Cephal-odd.

Reproductive strategy is probably irrelevant other than as is applies to extremes in modern cephalopods. We can only surmise the strategies that fossil forms used. Two characters do apply, one is a spherical protococh lacking a scar or cicatrix, followed by a constriction and two, a radula with 9 elements per row.

Based on the phragmocone, orthocerids and lituitids are true nautiloids; septa are saucer shaped and concave forward and septal necks are retrosiphonate, pointing backwards. So we have a case where the nautiloid - non-nautiloid distinction overlaps with the palcephalopod - neocephalopod distinction.

The R/K selection theory article is overyly complex, full of theory (hypotheses) and written to and for specialists in the particular field and not really for an educated general audience.

cheers JM (talk) —Preceding undated comment added 13:55, 2 October 2009 (UTC).

Thanks for the comments. I agree that life cycles are more speculative than morphology, and the article should be clear about what is conjectural. The speculation is not baseless, though. Neocephalopod nautiloids do tend to have smaller apices than the relatives of the nautilus, which suggests a smaller hatching size. There has been more recent work on immature nautiloids from the Paleozoic, which provides some insight into their ontogeny. There's also some evidence that Ordovician orthocerids and lituitids were more pelagic than other nautiloids from the same time. Soon I'll do some rewriting to clarify your point and cite new references.

You're right that the two classifications overlap, and neocephalopods include some groups traditionally considered nautiloids. Since we are accommodating different philosophies of classification, and the relationships of many nautiloid groups are unresolved, I think it best to embrace the contradiction and explain in the article which classification we are using at the time.

Cheers, Cephal-odd (talk) 17:10, 28 October 2009 (UTC)

By the way, I agree that the article about r & K selection seems very technical. If we refer to it, we should summarize the concept for a lay audience. Cephal-odd (talk) 17:13, 28 October 2009 (UTC)

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Restoring ammonoids & coleoids to this group

Some time ago, this article was edited to make Neocephalopoda appear to be solely a nautiloid group that excludes coleoids and ammonoids. But Neocephalpoda was originally coined to include both those groups, as the cited sources state. Excluding those taxa also contradicts the rest of the article.

While the hypothesis may not be correct for early Paleozoic taxa (since some have argued that the split between the coleoid and Nautilus lineages didn't happen till the Silurian or so), there still seems to be general agreement that ammonoids and coleoids both evolved from orthocerid-like nautiloids via the bactritids.

Cheers, Cephal-odd (talk) 17:34, 30 May 2018 (UTC)