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The majority of ammonite species feature planispiral shells, tightly coiled in a flat plane. The most fundamental difference in spiral form is how strongly successive whorls expand and overlap their predecessors. This can be inferred by the size of the umbilicus, the sunken-in inner part of the coil, exposing older and smaller whorls.
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).
This list of ammonites is a comprehensive listing of genera that are included in the subclass †Ammonoidea, excluding purely vernacular terms. The list includes genera that are commonly accepted as valid, as well as those that may be invalid or doubtful ( nomina dubia ), or were not formally published ( nomina nuda ), as well as junior ...
The primary difference lies in the aperture, which in the microconch has planar extensions on either side, lappets. ... Zone, Clatcombe, Dorset, UK. Size of ammonite ...
Goniatitinae is one of six subfamilies into which the Goniatitidae is subdivided according to Miller, Furnish, and Schindewolf, 1957. The diagnostic character is the narrow bifurcated (double pronged) ventral lobe of the suture, which lies along the outer rim.
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Goniatitoidea, formerly Goniatitaceae in older publications, is a superfamily of late Paleozoic ammonoid cephalopods included in the Goniatitida.They are characterized by thinly discoidal to globular shells with variable umbilici and sculpture.
Parapuzosia seppenradensis is the largest known species of ammonite. [1] It lived during the Lower Campanian Epoch of the Late Cretaceous period, in marine environments in what is now Westphalia, Germany.