Ammonitida is an order of
ammonoid
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...
cephalopods that lived from the
Jurassic through
Paleocene time periods, commonly with intricate
ammonitic sutures.
Ammonitida is divided into four suborders, the
Phylloceratina,
Lytoceratina,
Ancyloceratina, and
Ammonitina.
The Phylloceratina is the ancestral stock, derived from the
Ceratitida near the end of the
Triassic. The Phylloceratina gave rise to the Lytoceratina near the beginning of the Jurassic which in turn gave rise to the highly specialized Ancyloceratina near the end of the Jurassic. Both the Phylloceratina and Lytoceratina gave rise to various stocks combined in the Ammonitina.
These four suborders are further divided into different stocks, comprising various families combined into superfamilies. Some like the
Hildoceratoidea and
Stephanoceratoidea are restricted to the Jurassic. Others like the
Hoplitoidea
Hoplitoidea, formerly Hoplitaceae, is a superfamily of mostly Upper Cretaceous ammonites comprising families united by a similar suture pattern with multiple similar elements that tend to decrease in size going toward the umbi ...
and
Acanthoceratoidea are known only from the Cretaceous. Still others like the
Perisphinctoidea
Perisphinctoidea, formerly Perisphinctaceae, is a superfamily of Middle Jurassic (Bajocian) to Lower Cretaceous (Barremian) ammonites, commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the ven ...
are found in both.
References
*Arkell ''et al.'', 1957. Mesozoic Ammonoidea;
Treatise on Invertebrate Paleontology, Part L, Ammonoidea. Geol Soc of America and Univ. Kansas press. R.C. Moore (Ed).
Classification of N. H. Landman et al. 2007
Ammonite taxonomy
Cephalopod orders
Jurassic first appearances
Paleocene extinctions
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