Editing Nautiloid (section)

==Fossil record==
[[Image:Nautiloid trilacinoceras.jpg|thumb|Fossil nautiloid ''[[Trilacinoceras]]'' from the [[Ordovician]] of [[China]].]]
[[Image:OrdNautiloidInternalMold.jpg|thumb|Fossil orthoconic nautiloid from the [[Ordovician]] of [[Kentucky]]; an internal mold showing siphuncle and half-filled camerae, both encrusted.]]
[[Image:OrhtocerasNautiloid092313.jpg|thumb|Cross-section of an ''[[Orthoceras]]'' nautiloid from the Siluro-Devonian of Erfoud, Morocco.]]
Nautiloids are often found as [[fossil]]s in early [[Palaeozoic]] rocks (less so in more recent strata).

The rocks of the [[Ordovician]] period in the [[Baltic Sea|Baltic coast]] and parts of the United States contain a variety of nautiloid fossils, and specimens such as ''[[Discitoceras]]'' and ''Rayonnoceras'' may be found in the [[limestone]]s of the [[Carboniferous]] period in [[Republic of Ireland|Ireland]]. The marine rocks of the [[Jurassic]] period in [[United Kingdom|Britain]] often yield specimens of ''Cenoceras'', and nautiloids such as ''[[Eutrephoceras]]'' are also found in the Pierre Shale formation of the [[Cretaceous]] period in the north-central United States.

Specimens of the [[Ordovician]] nautiloid ''[[Endoceras]]'' have been recorded measuring up to {{convert|5.7|m|ft|abbr=off|sp=us}} in shell length, and there is a description of a specimen estimated to have reached {{convert|9.1|m|ft|abbr=off|sp=us}}, although that specimen is reported as destroyed.<ref>{{Cite journal |last1=Klug |first1=Christian |last2=De Baets |first2=Kenneth |last3=Kröger |first3=Björn |last4=Bell |first4=Mark A. |last5=Korn |first5=Dieter |last6=Payne |first6=Jonathan L. |date=2015 |title=Normal giants? Temporal and latitudinal shifts of Palaeozoic marine invertebrate gigantism and global change |url=https://onlinelibrary.wiley.com/doi/10.1111/let.12104 |journal=Lethaia |language=en |volume=48 |issue=2 |pages=267–288 |doi=10.1111/let.12104|bibcode=2015Letha..48..267K |url-access=subscription }}</ref> These large nautiloids would have been formidable predators of other marine animals at the time they lived.

In some localities, such as [[Scandinavia]] and [[Morocco]], the [[fossil]]s of [[orthocone|orthoconic]] nautiloids accumulated in such large numbers that they form limestones composed of nonspecific assemblages known as ''cephalopod beds'', ''cephalopod limestones'', ''nautiloid limestones'', or ''Orthoceras limestones'' in the geological literature. Although the term ''[[Orthoceras]]'' now only refers to a [[Baltic Sea|Baltic coast]] [[Ordovician]] genus, in prior times it was employed as a general name given to all [[orthoconic|straight-shelled]] nautiloids that lived from the Ordovician to the [[Triassic]] periods (but were most common in the early [[Paleozoic]] era).