Agoniatitida
Agoniatitida, also known as the Anarcestida, is the ancestral order within the cephalopod subclass Ammonoidea originating from bactritoid nautiloids, that lived in what would become Africa, Asia, Australia, Europe, and North America during the Devonian from about the lower boundary of Zlichovian stage into Taghanic event during upper middle Givetian, existing for approximately 25 million years.
Taxonomic nomenclature
The Order Agoniatitida, named by Ruzhencev, 1957, is a subjective synonym for the Order Anarcestida, named by Miller and Furnish, 1954. Accordingly, the name Anarcerstida is based on the family Anarcestidae of Steinmann 1890. That of Agoniatiida is based on the family Agnoniatidae of Holzapfel, 1899.Saunders, Work, and Nikolaeva, 1999, refer to the Anarcestida, with Agoniatina a suborder, maintaining the priority as found in the Treatise. Shevyrev, 2006 on the other hand follows Ruzhencev, 1957 and used Agonititida.