ammonoid

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  • noun

Synonyms for ammonoid

one of the coiled chambered fossil shells of extinct mollusks

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1) Ammonoids have an exceptionally good fossil record.
3) Ammonoids evolved to have more complex suture patterns--and, thus, stronger shells--through time.
4) Ammonoids were devastated by the largest extinction in Earth's history, at the end of the Permian Period, as well as Late Cretaceous mass extinction.
2) One of the chambers of the ammonoid was used as a living space and the rest were used to regulate buoyancy, just like in a submarine.
The surveys in the present study indicate that more than 800 ammonoids and 300 belemnoids are present in the tile of the shopping complex.
One of the underlying goals of the present study was to give undergraduate students hands-on experimental involvement by having them compare their research and findings with the important earlier work on the coiling of ammonoids presented by David Raup (1967) in The Journal of Paleontology.
The distinctive folded septa allow for relatively easy identification, and ammonoids are commonly used as index fossils for the Mesozoic.
Raup (1967) determined that the shape of >405 genera of extinct ammonoids clustered around a geometry of W = 2 and D = 0.
45) commented that "it is often impossible to estimate the shape of the non-existent portion of the generating curve" when measuring shell geometry; nevertheless, the use of ammonoids that have been cut lengthwise and cross sectioned as part of the manufacture of the building stones presented in this study minimizes this problem.
To conduct this analysis, the instructor subdivided the floor space at the retail center into corridors so that students would never be sampling (measuring) the same ammonoids.
Finally, it was hoped that the different groups of ammonoids could be differentiated between the two varieties of limestones used on the property, assuming that they came from different localities or formations.
Raup (1967) found that the majority of his 405 genera of ammonoids clustered around a geometry of W = 2 and D = 0.
Ammonoids that were not bisectioned through the plane of symmetry will have artificially inflated expansion ratios because the full (maximum) dimensions of the chambers are not being measured (Figure 6).
As the distribution of ammonoid geometries presented in Figures 3, 4, and 5 suggests, there are environmental restrictions on shell shapes, and the ammonoids used only a fraction of the total geometric continuum available.