Agathiceras
''Agathiceras'' is a subglobose goniatitida, goniatitid from the family Agathiceratidae, widespread and locally abundant in Lower Pennsylvanian to Middle Permian sediments, e.g. the Urals, Sicily, and Texas (Blaine Formation). ''Agathiceras'', named by Gemmellaro in 1887 from the Middle Permian Sicilian species, ''Agathiceras suessi, A. suessi'', has a broadly rounded outer edge, known as the venter, being at the lower side of the animal during life, and a deeply impressed innerside, the dorsum which corresponds with the back or dorsal side of the animal. The sutures are goniatitic with three lateral and one dorsolateral lobes on either side. Those that are external are spatulate, those hidden are V-shaped. The siphuncle is primitive with the septal necks pointing to the rear, a condition known as retrosiphonate. ''Agathiceras'' is thought to be derived from ''Proshumardites'' according to Saunders ''et al''. (1999), which is thought to be derived from ''Dombarites''; all of w ...
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