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Three dimensional reconstructions of Nummulites tests reveal complex chamber shapes.

Renema W, Cotton L - PeerJ (2015)

Bottom Line: During the Paleogene the genus Nummulites was particularly abundant with a global distribution, leading it to be frequently used in biostratigraphy.Here we apply micro computed-tomographical scanning, a tool that recently has become available, to visualise 3D chamber shape of Nummulites djokdjokartae and compare these to traditional morphometrical characters.We argue that 3D reconstructions of Nummulites tests will be a great aid in improving our understanding of lineages within the genus Nummulites, and to elucidate its evolutionary and biogeographical history.

View Article: PubMed Central - HTML - PubMed

Affiliation: Naturalis Biodiversity Center , CR Leiden , The Netherlands.

ABSTRACT
Larger benthic foraminifera (LBF) are important and prolific carbonate producers both in modern and ancient shallow tropical seas. During the Paleogene the genus Nummulites was particularly abundant with a global distribution, leading it to be frequently used in biostratigraphy. However, their evolution is poorly understood as classification is Europe-centered and mostly based on external characters and equatorial thin sections. New occurrences from regions outside the northern Tethys which poorly fit in thus reference frame, show that a more rigid framework for the classification of Nummulites is needed. Here we apply micro computed-tomographical scanning, a tool that recently has become available, to visualise 3D chamber shape of Nummulites djokdjokartae and compare these to traditional morphometrical characters. We find that despite the regular shape in equatorial and axial thin section the irregular 3D chamber shape is not predicted by these sections. We argue that 3D reconstructions of Nummulites tests will be a great aid in improving our understanding of lineages within the genus Nummulites, and to elucidate its evolutionary and biogeographical history.

No MeSH data available.


Related in: MedlinePlus

Chamber shape per whorl in specimen 06KW01_19.Note the difference with specimen 06KW01_05 (Fig. 2). (A) whorl 1; (B) whorl 2; (C) whorl 3; (D) whorl 4; (E) whorl 5; (G) first half of whorl 6. 3D movies of this figure are in the SOM.
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fig-3: Chamber shape per whorl in specimen 06KW01_19.Note the difference with specimen 06KW01_05 (Fig. 2). (A) whorl 1; (B) whorl 2; (C) whorl 3; (D) whorl 4; (E) whorl 5; (G) first half of whorl 6. 3D movies of this figure are in the SOM.

Mentions: Macrospheric specimens of Nummulites djokdjokartae have a very regular appearance in both equatorial horizontal and axial thin section. Equatorial section there are 4–6 whorls with chambers with almost straight septa and chamber shape which changes from being higher than long in the initial whorl to longer than high in the later whorls. In axial section there are stacks of alar prolongations of very similar height visible throughout the test, including the polar region. In traditional growth models of Nummulites with the chambers converging in the polar region, it is expected that alar prolongations narrow towards the center and often a polar pillar is present. Although the regularity of the stack of alar prolongations gives the impression that all chambers have long alar prolongations aligned next to each other, when the 3D reconstructions of the chambers are examined, it becomes clear that frequently alar prolongations of non-successive chambers are aligned next to each other in the central part of the test, and that sometimes the same alar prolongation transverses an axial plane multiple times (Figs. 2 and 3). In axial thin section the test appears symmetrical, but other than the first ten or so regular chambers, all chambers are asymmetrical in the equatorial plane. This does not conform the description of the genus Nummulites, which includes involute, biconvex, planispiral coiling (Loeblich & Tappan, 1988; Schaub, 1981). Depending on the distribution of this character within Schaub’s phyla, an emendation of the description of Nummulites might be needed.


Three dimensional reconstructions of Nummulites tests reveal complex chamber shapes.

Renema W, Cotton L - PeerJ (2015)

Chamber shape per whorl in specimen 06KW01_19.Note the difference with specimen 06KW01_05 (Fig. 2). (A) whorl 1; (B) whorl 2; (C) whorl 3; (D) whorl 4; (E) whorl 5; (G) first half of whorl 6. 3D movies of this figure are in the SOM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493699&req=5

fig-3: Chamber shape per whorl in specimen 06KW01_19.Note the difference with specimen 06KW01_05 (Fig. 2). (A) whorl 1; (B) whorl 2; (C) whorl 3; (D) whorl 4; (E) whorl 5; (G) first half of whorl 6. 3D movies of this figure are in the SOM.
Mentions: Macrospheric specimens of Nummulites djokdjokartae have a very regular appearance in both equatorial horizontal and axial thin section. Equatorial section there are 4–6 whorls with chambers with almost straight septa and chamber shape which changes from being higher than long in the initial whorl to longer than high in the later whorls. In axial section there are stacks of alar prolongations of very similar height visible throughout the test, including the polar region. In traditional growth models of Nummulites with the chambers converging in the polar region, it is expected that alar prolongations narrow towards the center and often a polar pillar is present. Although the regularity of the stack of alar prolongations gives the impression that all chambers have long alar prolongations aligned next to each other, when the 3D reconstructions of the chambers are examined, it becomes clear that frequently alar prolongations of non-successive chambers are aligned next to each other in the central part of the test, and that sometimes the same alar prolongation transverses an axial plane multiple times (Figs. 2 and 3). In axial thin section the test appears symmetrical, but other than the first ten or so regular chambers, all chambers are asymmetrical in the equatorial plane. This does not conform the description of the genus Nummulites, which includes involute, biconvex, planispiral coiling (Loeblich & Tappan, 1988; Schaub, 1981). Depending on the distribution of this character within Schaub’s phyla, an emendation of the description of Nummulites might be needed.

Bottom Line: During the Paleogene the genus Nummulites was particularly abundant with a global distribution, leading it to be frequently used in biostratigraphy.Here we apply micro computed-tomographical scanning, a tool that recently has become available, to visualise 3D chamber shape of Nummulites djokdjokartae and compare these to traditional morphometrical characters.We argue that 3D reconstructions of Nummulites tests will be a great aid in improving our understanding of lineages within the genus Nummulites, and to elucidate its evolutionary and biogeographical history.

View Article: PubMed Central - HTML - PubMed

Affiliation: Naturalis Biodiversity Center , CR Leiden , The Netherlands.

ABSTRACT
Larger benthic foraminifera (LBF) are important and prolific carbonate producers both in modern and ancient shallow tropical seas. During the Paleogene the genus Nummulites was particularly abundant with a global distribution, leading it to be frequently used in biostratigraphy. However, their evolution is poorly understood as classification is Europe-centered and mostly based on external characters and equatorial thin sections. New occurrences from regions outside the northern Tethys which poorly fit in thus reference frame, show that a more rigid framework for the classification of Nummulites is needed. Here we apply micro computed-tomographical scanning, a tool that recently has become available, to visualise 3D chamber shape of Nummulites djokdjokartae and compare these to traditional morphometrical characters. We find that despite the regular shape in equatorial and axial thin section the irregular 3D chamber shape is not predicted by these sections. We argue that 3D reconstructions of Nummulites tests will be a great aid in improving our understanding of lineages within the genus Nummulites, and to elucidate its evolutionary and biogeographical history.

No MeSH data available.


Related in: MedlinePlus