| Agoniatitida Temporal range: L-M Devonian |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | Ammonoidea |
| Order: | Agoniatitida Ruzhencev, 1957 |
Agoniatitida, also known as the Anarcestida, is the ancestral order within the cephalopod Subclass Ammonoidea, that lived in what would become Africa, Asia, Australia, Europe, and North America during the Devonian from about 410—385 mya, existing for approximately 25 million years.
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The Order Agoniatitida, named by Ruzhencev, 1957,[1] is a subjective synonym for the Order Anarcestida, named by Miller and Furnish, 1954.[2] Accordingly the name Anarcerstida is based on the family Anarcestidae (ex Anarcestinae) of Steinmann 1890. That of Agoniatiida is based on the family Agnoniatidae of Holzapfel, 1899.
Saunders, Work, and Nikolaeva, 1999,[3] refer to the Anarcestida, with Agoniatina a suborder, maintaining the priority as found in the Treatise. Shevyrev, 2006 [4] on the other hand follows Ruzhencev, 1957 and used Agonititida.
Agoniatitida are primitive ammonoids with a ventral retrochoanitic siphuncle (septal necks point to the rear) reflective of their nautiloid ancestors.and goniatitic sutures with a variable number of lobes. Shells vary from discoidal to globular. Coiling may be loose with whorls barely touching or tight with a dorsal impression.[2]
Fossils were restricted to the strata of the Zlichovian to Famennian ages.