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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

Virtual equatorial (A, B) and axial (C, D) sections of specimen 06KW01_02 (type A1; A, C) and 06KW0110 (type A2; B, D).Scale bars represent 0.5 mm.
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fig-6: Virtual equatorial (A, B) and axial (C, D) sections of specimen 06KW01_02 (type A1; A, C) and 06KW0110 (type A2; B, D).Scale bars represent 0.5 mm.

Mentions: No morphological differences were found between the four samples examined, hence all specimens are treated as coming from a single population. In equatorial sections chamber shape changed from almost square (width is similar to height) to elongated (width is up to 3 times longer than height). In nearly all specimens square chambers formed less than a whorl, resulting in a straight line in the whorl diagram (Fig. 4). However, based on total number of whorls and proloculus diameter two groups can be recognized, group A1 with a proloculus size of smaller than 400 µm, and more than 5 whorls, and group A2 with a proloculus larger than 400 µm and fewer than 5 whorls (Fig. 5). The marginal cord is placed in a slightly undulating plane perpendicular to the coiling. Especially in group A1 the outermost whorls are bent out of the plane of coiling. The general morphology in both groups includes several initial chambers that are as high as long, followed by 3–5 whorls with chambers that are up to 3 times longer than high (Figs. 6A and 6B). Overall this results in an increase in chamber length and a comparable number of chambers per whorl in whorls 3–5, despite the increase in radius (Fig. 7A). Chamber length is variable though, with occasional very narrow chambers or split septa (Figs. 6 and 7B). Proximal and distal angle of the septa is comparable in all specimens. The total number of chambers differ between the A1 and A2 group; specimens in A1 have 130–150 chambers and those in A2 90–110 chambers.


Three dimensional reconstructions of Nummulites tests reveal complex chamber shapes.

Renema W, Cotton L - PeerJ (2015)

Virtual equatorial (A, B) and axial (C, D) sections of specimen 06KW01_02 (type A1; A, C) and 06KW0110 (type A2; B, D).Scale bars represent 0.5 mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig-6: Virtual equatorial (A, B) and axial (C, D) sections of specimen 06KW01_02 (type A1; A, C) and 06KW0110 (type A2; B, D).Scale bars represent 0.5 mm.
Mentions: No morphological differences were found between the four samples examined, hence all specimens are treated as coming from a single population. In equatorial sections chamber shape changed from almost square (width is similar to height) to elongated (width is up to 3 times longer than height). In nearly all specimens square chambers formed less than a whorl, resulting in a straight line in the whorl diagram (Fig. 4). However, based on total number of whorls and proloculus diameter two groups can be recognized, group A1 with a proloculus size of smaller than 400 µm, and more than 5 whorls, and group A2 with a proloculus larger than 400 µm and fewer than 5 whorls (Fig. 5). The marginal cord is placed in a slightly undulating plane perpendicular to the coiling. Especially in group A1 the outermost whorls are bent out of the plane of coiling. The general morphology in both groups includes several initial chambers that are as high as long, followed by 3–5 whorls with chambers that are up to 3 times longer than high (Figs. 6A and 6B). Overall this results in an increase in chamber length and a comparable number of chambers per whorl in whorls 3–5, despite the increase in radius (Fig. 7A). Chamber length is variable though, with occasional very narrow chambers or split septa (Figs. 6 and 7B). Proximal and distal angle of the septa is comparable in all specimens. The total number of chambers differ between the A1 and A2 group; specimens in A1 have 130–150 chambers and those in A2 90–110 chambers.

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