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Tragodesmoceras
''Tragodesmoceras'' is a large moderately involute Ammonitida, ammonite with deeply embracing whorls that are higher than wide, a steep sided umbilicus and a narrowly rounded venter. Ornament consists of primary ribs that begin at the umbilical shoulder and smaller secondary ribs that begin mid flank. Ribs are sigmodal, periodically thickened and bent forward on the outer flank to cross the venter as chevrons. The suture has a broad trifid lateral lobe. Species include ''Tregodesmoceras clypealoides'' (type), known from western Europe and the U.S., ''Tragodesmosderas bassi'', known from Arizona and Kansas, and ''Tragodesoceras socorroense'' known from Arizona and New Mexico. The related ''Muniericeras'' is more evolute in form, but otherwise similar. References * W.J. Arkell, et al., 1957. Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology Part L Mollusca 4. Geological Society of America and University of Kansas Press. * William A Cobban & Stephen C. Hook. 1983. . ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonitida
Ammonitida, or true ammonites, are an order of Ammonoidea, 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 Peris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |