ammonoid


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Related to ammonoid: ammonite, Ammonoidea

ammonoid

[′a·mə‚nȯid]
(paleontology)
A cephalopod of the order Ammonoidea.
References in periodicals archive ?
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.
A general description of the ammonoid dimensions present in the tile, as well as the internal geometry, is presented in Tables 2 and 3, respectively.
This valuable, if underappreciated, data set can be compared with earlier important work on cephalopod geometry presented in manuscripts such as those of Raup (1967) and Chamberlain (1976), allowing students to compare their own measured and compiled ammonoid data set with the data in the literature.
Other pedagogical exercises might involve having students use the ammonoid and belemnoid characteristics to determine the age of the flooring tile.
Students found that the majority of the ammonoids present in the tile of Southpark Mall fell within the abundance contours presented in Raup (1967; Figure 5) and that there was little difference between the ammonoid geometry between the two varieties of tile.
Learning outcomes were threefold for this exercise: (1) students increased their understanding of functional morphology and growth strategy of ammonoids, especially with respect to hydrodynamic streamlining and swimming stability; (2) students compared their findings with earlier reported findings related to ammonoid coiling strategies, allowing students to both critique the earlier work and gain insights into the methods and limits of the scientific method in the historical sciences; and (3) students learned about proper specimen selection to avoid data-set contamination and sampling error.
The primary decorative stone, ~80% by surface area, is a light beige limestone that contains abundant ammonoids and belemnoids (Figure 1).
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.
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).