The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 407.6 ± 2.6 million years ago to 393.3 ± 1.2 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after the Ems river in Germany. The GSSP is located in the Zinzil'ban Gorge in the Kitab State Geological Reserve of Uzbekistan , 35 centimetres (14 in) above the contact with the Madmon Formation .
5-490: In North America the Emsian Stage is represented by Sawkill or Sawkillian time. During this period, earliest known agoniatitid ammonoid fossils began appearing within this stage after first appearing in previous stage and began to evolutionarily radiate within this stage, in which a new ammonoid order Goniatitida rises in the end of Zlichovian stage (Siberian representation; corresponds to early Eifelian and after
10-532: Is a subjective synonym for the Order Anarcestida, named by Miller and Furnish, 1954. 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, refer to the Anarcestida, with Agoniatina a suborder, maintaining the priority as found in
15-641: 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 (corresponding to late Pragian , after 409.1 mya ) into Taghanic event during upper middle Givetian (between 385 and 384 mya), existing for approximately 25 million years. The Order Agoniatitida, named by Ruzhencev, 1957,
20-466: The Treatise. Shevyrev, 2006 on the other hand follows Ruzhencev, 1957 and used Agonititida. Agoniatitids 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
25-624: The end of Early Devonian, before 391.9 mya ). Later agoniatitid ammonoids would die out in the Taghanic event in the upper middle Givetian . Goniatite ammonoids would give rise to further ammonoid orders, thus starting ammonoid dominance of marine fossils in further periods until their end at the Cretaceous-Paleogene mass extinction event . This geochronology article is a stub . You can help Misplaced Pages by expanding it . Agoniatitida Agoniatitida , also known as
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