Ammonitida

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(Taxonomy: changed wording)
(Phylogeny: corrections)
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==Phylogeny ==  
==Phylogeny ==  
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The prevailing consensus is that the Ammonitida are derived from, or at least split from, the [[Lytoceratida]] near the beginning of the Jurassic Period, and not long after one or the other spit off from the [[Phylloceratida]] which extends throughout almost the entire Mesozoic.  
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The prevailing consensus is that the Ammonitida are derived from [[Lytocerida]] near the beginning of the Jurassic Period, not long after the Lytocerida split off from the [[Phyllocerida]] which extends throughout almost the entire Mesozoic.  
The Psilocerataceae which are confined to the Lower Jurassic are the earliest of the ammonitids. Their origin is unsure of although they are shown derived from the Phylloceratida in the older Treatise. Apparently they gave rise to no subsequent groups.
The Psilocerataceae which are confined to the Lower Jurassic are the earliest of the ammonitids. Their origin is unsure of although they are shown derived from the Phylloceratida in the older Treatise. Apparently they gave rise to no subsequent groups.
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The main phyllogenetic sequence begins in the Lower Jurassic with the Eoderocerataceae which gave rise to the Lower and lower Middle Jurassic Hildocerataceae. The Hildocerataceae in turn gave rise to the mostly Middle Jurasic Stephanocerataceae and to the Middle Jurassic to Cretaceous Perisphinctaceae and Haplocerataceae. The Hammatocerataceae may be a subgroup of the Hildocerataceae.
The main phyllogenetic sequence begins in the Lower Jurassic with the Eoderocerataceae which gave rise to the Lower and lower Middle Jurassic Hildocerataceae. The Hildocerataceae in turn gave rise to the mostly Middle Jurasic Stephanocerataceae and to the Middle Jurassic to Cretaceous Perisphinctaceae and Haplocerataceae. The Hammatocerataceae may be a subgroup of the Hildocerataceae.
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The origin of the mostly Lower Cretaceous Desmocerataceae is left uncertain, but a considered to have given rise to the Upper Cretaceous Hoplitaceae from which the Pulchelliaceae have been split, and to the Acanthocerataceae which includes some of the latest ammonites.                                                                
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The origin of the mostly Lower Cretaceous Desmocerataceae is left uncertain, but a considered to have given rise to the Upper Cretaceous Hoplitaceae from which the Pulchelliaceae have been split, and to the Acanthocerataceae which includes some of the latest ammonites.
==Study and application==
==Study and application==

Revision as of 18:45, 8 April 2013

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