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Alcidellus
''Alcidellus'' is an oxyconic (sharp ventered) haploceratacean ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ... from the Middle Jurassic. ''Alcidellus'' was named as a genus buy Gerd Westermann in 1958. It is now generally seen as a subgenus of '' Oxycerites'', differing from ''Oxyceratites (O)'' in having a broader venter with ventrolateral shoulders. The shell of ''Oxycerites'', including ''O (Alcidellus)'' is generally smooth, essentially involute with a small umbilicus, highly compressed with flanks converging on a narrow, somewhat sharp venter. Sutures are ammonitic. ''References'' ;Notes ;Publications * An Early Bathonian Tethyan Ammonite Fauna from Argentina, by Alberto C Riccardi and Gerd E.G. Westermann. Palaeontology, Volume 42. no2, pub online 21 Nov 2003* U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haplocerataceae
Haploceratoidea, formerly Haplocerataceae, is an extinct superfamily of ammonoid cephalopods belonging to the Ammonitida that unites three families, Strigoceratidae, Oppeliidae, and Haploceratidae, listed below. Haploceratoidea begins with all three families in the lower Middle Jurassic, Bajocian. Strigoceratidae is limited to the Bajocian but Oppeliidae, and Haploceratidae extend through the remaining Jurassic, well into the Cretaceous; the Oppeliidae into the middle Albian, the Haplocertidae only into the Valanginian. Diagnosis Haploceratoidea are typically compressed, discoidal Ammontida that may be keeled or unkeeled, tending to be oxyconic, with usually falcoid or falcate ribbing. The aptychi are paired and differ between families and have been found ''in situ'' in e.g. '' Oppelia subrudiata'' and in '' Pseudolissoceras''. Taxonomy The Origin of the Haploceratoidea is undetermined but it is likely all three component families have their beginnings in the Hammatoceratidae ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonitida
Ammonitida is an order of ammonoid cephalopods that lived from the Jurassic through Paleocene time periods, commonly with intricate ammonitic sutures. Ammonitida is divided into four suborders, the Phylloceratina, Lytoceratina, Ancyloceratina, and Ammonitina. The Phylloceratina is the ancestral stock, derived from the Ceratitida near the end of the Triassic. The Phylloceratina gave rise to the Lytoceratina near the beginning of the Jurassic which in turn gave rise to the highly specialized Ancyloceratina near the end of the Jurassic. Both the Phylloceratina and Lytoceratina gave rise to various stocks combined in the Ammonitina. These four suborders are further divided into different stocks, comprising various families combined into superfamilies. Some like the Hildoceratoidea and Stephanoceratoidea are restricted to the Jurassic. Others like the Hoplitoidea and Acanthoceratoidea are known only from the Cretaceous. Still others like the Perisphinctoidea are found in both. R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxycerites
''Oxycerites'' is an extinct ammonoid cephalopod belonging to the haploceratoid family, Oppeliidae Oppeliidae are compressed to oxyconic, sculptured Haploceratoidea, either unkeeled, unicarinate, bicarinate, or tricarinate; with sutures in great variety, but ribbing usually more or less falcoid or falcate. The Oppeliidae is the principal famil ..., that lived during the Middle Jurassic. Shells of ''Oxycerites'' are involute, compressed and generally smooth with a sharply rounded venter on the outer rim, deeply impressed dorsum on the inner rim, and a small umbilicus. The living chamber takes up slightly more than half a whorl. ''Oxycerites'' grew to a diameter of at least 17.5 cm, about 7 inches. '' Oppelia'' and '' Oecotraustes'' are similar and closely related forms. ''Oppelia'' is smoother, ''Oecotraustes'' more strongly ribbed Distribution Jurassic of Argentina, France, Germany, Iran, Madagascar, Russia, Saudi Arabia and the United Kingdom References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |