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I miss the definition of ammonite. In my opinion, many authors confuse the term "Ammonite" and "Ammonoid". Ammonoids (Ammonoidea) are large group of cephalopods including for example goniatites (Goniatitida), ceratites (Ceratitida) and ammonites (Ammonitida?).

EDIT: If you think that ammonites and ammonoids are the same, you are not right. Notice that researchers try to avoid using the term ammonite when talking about paleozoic ammonoids. Ammonites are usually refered to jurassic and cretaceous ammonoids. "While goniatites proliferated during the Carboniferous, ammonites thrived in Mesozoic times." https://www.researchgate.net/publication/262048294_Goniatites

But how can we strictly define "true ammonite"? Is it because of the ammonitic suture? This way, many triassic, jurassic, creataceous and possibly paleogenic (danian) ammonoids could be called true ammonites, because they have complex (ammonitic) sutures.

Can we call all jurassic and cretaceous ammonoids (phylloceratina, psiloceratina, lytoceratina, ammonitina, haploceratina, perisphinctina and ancyloceratina) ammonites? Can you show me where ammonites are on phylogenetic tree?

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    $\begingroup$ Perhaps better asked on the Biology site? $\endgroup$
    – jamesqf
    May 8, 2019 at 17:31
  • $\begingroup$ Tags are for reference so those specialized in a particular field can find your question easily. not for including all related vocabulary. $\endgroup$
    – John
    May 8, 2019 at 19:58
  • $\begingroup$ You may find this helpful. link.springer.com/chapter/10.1007/978-1-4757-9153-2_1 $\endgroup$
    – John
    May 8, 2019 at 20:04
  • $\begingroup$ No that does not answer my question thanks. $\endgroup$
    – Petr Hykš
    May 8, 2019 at 20:05
  • $\begingroup$ From everything I've found, ammonite and ammonoid are synonyms. $\endgroup$
    – David Hammen
    May 9, 2019 at 13:05

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There is no strict definition of ammonites

Ammonites are not strictly defined. One can reffer to ammonites as to the whole group of ammonoids (Ammonoidea, ammonites sensu latto). This is common, but not supported by most researchers. Researchers use the term "ammonoid" for paleozoic ammonoidea and "ammonite" for Jurassic and Cretaceous Ammonoidea (ammonites sensu stricto). Ammonites sensu stricto reffer to ammonoids with complex (ammonitic) sutures, which are typical for Jurassic and Cretaceous ages. However, complex ammonitic sutures are not exclusive for Jurassic and Cretaceous ammonoids. Ceratitic sutures are not exclusive for Triassic either and occur in Jurassic ammonoids, too.

So caution must be exercised when using suture lines as a means of classification. To obviate some of the problems posed by this simplistic classification, Wedekind, in 1918, introduced the terms palaeo-, meso- and neoammo-noids to classify ammonoids better.

(PDF) Goniatites. Available from: https://www.researchgate.net/publication/262048294_Goniatites [accessed May 10 2019].

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