Growth Rate Biometric Quantifi cation by X-ray Microtomography on Larger Benthic Foraminifera: Three-dimensional Measurements Push Nummulitids into the Fourth Dimension

Author(s)

Antonino Briguglio, Johann Hohenegger, Brian Metscher

Abstract

Th is work demonstrates the potential of three-dimensional biometric quantifi cation using microtomography

on larger benthic foraminifera. We compare traditional linear and area measures used for calculating three-dimensional

characters with actual 3D measurements made from volume images obtained using X-ray microtomography (microCT).

Two specimens of recent larger benthic foraminifera, i.e., Palaeonummulites venosus and Operculina ammonoides,

were imaged with a high-resolution microCT scanner. Th is method enables three-dimensional imaging and calculation

of measurements like 3D distances, surfaces and volumes.

Th e quantitative high-resolution images enabled the extraction of the lumina from the proloculus to the last

complete scanned chamber and of the canal system spreading into marginal chord and septa. External surfaces and

volumes were calculated on the extracted parts. Th ese measurements allowed the calculation of porosity and microporosity

to obtain the test density, which is the basis for many inferences about foraminifera, e.g., reconstructions

of transport and deposition. Volume and surface measurements of the proloculus allow the calculation of sphericity

deviation, which is useful for determining evolutionary trends in species based on individuals resulting from asexual

reproduction (A forms).

Th e three-dimensional data presented here show the actual growth of the foraminiferal cell and the development of

the test. Measurements made on an equatorial section cannot be considered representative of a three-dimensional test,

unless a correspondence between 2D data with 3D data shows signifi cant correlation. Chamber height, septal distance,

spiral growth and chamber area were measured on the equatorial section and correlated with the volume measurements

from 3D images to determine the predictive value of the 1D and 2D measures for estimating the 3D morphological

parameters.

In particular, we show that the equatorial section area of chambers correlates signifi cantly with the chamber

Organisation(s)

Department of Palaeontology

Journal

Turkish Journal of Earth Sciences

Volume

20

Pages

683-699

No. of pages

17

ISSN

1300-0985

DOI

https://doi.org/10.3906/yer-0910-44

Publication date

2011

Peer reviewed

Yes

Austrian Fields of Science 2012

105118 Palaeontology

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