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A primary difference between ammonites and nautiloids is the siphuncle of ammonites (excepting Clymeniina) runs along the ventral periphery of the septa and camerae (i.e., the inner surface of the outer axis of the shell), while the siphuncle of nautiloids runs more or less through the center of the septa and camerae.
It was once estimated that, if complete, this specimen would have had a diameter of approximately 2.55 m (8.4 ft) [2] or even 3.5 m (11 ft). [3] However, a study in 2021 estimated the diameter of the largest specimens to be around 2 m (6.6 ft). [ 4 ]
Parapuzosia is an extinct genus of desmoceratid ammonites from the Cenomanian to the Campanian of Africa, Europe, and North America. [2] They are typically very large ammonites, reaching diameters of 60 cm (2.0 ft) or more, with the largest species measuring around 2 m (6.6 ft). [3]
Goniatite shells are small to medium in size, almost always less than 15 centimeters (5.9 inches) in diameter and often smaller than 5 centimeters (2.0 inches) in diameter. The shell is always planispirally coiled, unlike those of Mesozoic ammonites in which some are trochoidal and even aberrant (called heteromorphs).
Most of the generic names in this list come from Jack Sepkoski's 2002 compendium of marine fossil genera, which can be corroborated by other sources such as Part L, Ammonoidea, in the Treatise on Invertebrate Paleontology. Additional generic names included come from the Treatise or various peer review scientific journals.
Ammonites — members of the Ammonoidea subclass of molluscan prehistoric cephalopods. Pages in this category should be moved to subcategories where applicable. This category may require frequent maintenance to avoid becoming too large.
Arietitidae is a family of true ammonites that make up part of the superfamily Psiloceratoidea, named after the type genus Arietites.They comprise medium-size to large or gigantic genera which in general are strongly ribbed, tuberculate in some, with keeled or grooved and keeled venters, and well differentiated ammonitic sutures.
Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology, Part L; Geological Society of America and University of Kansas press. C. W. Wright, J. H. Calloman, and M. K. Howarth. 1996. Cretaceous Ammonoidea. Treatise on Invertebrate Paleontology revised L(4):1-362; Media related to Ammonoceratites at Wikimedia Commons