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Hamites ("hook-like") is a genus of heteromorph ammonite that evolved late in the Aptian stage of the Early Cretaceous and lasted into the Cenomanian stage of the Late Cretaceous. The genus is almost certainly paraphyletic but remains in wide use as a "catch all" for heteromorph ammonites of the superfamily Turrilitoidea that do not neatly fit ...
The biology of the heteromorph ammonites is not clear, but one certainty is that their uncoiled shells would have made these forms very poor swimmers. Open shells, particularly ones with spines and ribs, create a lot of drag; but more importantly, the orientation of the shell, with the body hanging below the buoyant part of the shell, would ...
Heteroceras is a genus of Lower Cretaceous heteromorph ammonites belonging to the ancyloceratoidean family, Heteroceratidae. [1] Description
Ancyloceratidae is a family of heteromorphic ammonites that lived during the Early Cretaceous.Their shells begin as a loose spiral with whorls not touching which then turns into a straight shaft that ends in a J-shape hook or bend at end.
They are known as heteromorph shaped, with a partly uncoiled shell and the aperture directed toward the coiled part. Most ammonites are homomorph, as they maintain the same shape throughout the growth, while the ammonites in this genus have uncoiled shells ( heteromorph or different-shaped ammonites), that would have precluded fast swimming.
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Heteromorph ammonite Didymoceras stevensoni Life restoration of the heteromorph ammonite Diplomoceras with the plesiosaur Aristonectes Life restoration of the heteromorph Hyphantoceras Ammonoids with a shell shape diverging from the typical planispiral form are known as heteromorphs , instead forming a conch with detached whorls (open coiling ...
Bostrychoceras is a genus of heteromorph ammonite from the family Nostoceratidae. Fossils have been found in Late Cretaceous sediments in Europe and North America.. The shell of Bostrychoceras begins as a tightly wound helical spire, like that of Nostoceras, from which hangs a U- or J-shaped body chamber, at least in the adult.