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Critical appraisal of tubular putative eumetazoans from the Ediacaran Weng'an Doushantuo biota.

Cunningham JA, Vargas K, Pengju L, Belivanova V, Marone F, Martínez-Pérez C, Guizar-Sicairos M, Holler M, Bengtson S, Donoghue PC - Proc. Biol. Sci. (2015)

Bottom Line: Ramitubus and Crassitubus specimens preserve enigmatic cellular clusters at terminal positions in the tubes.Specimens of Sinocyclocyclicus and Ramitubus have biological features that might be cellular tissue or subcellular structures filling the spaces between the cross walls.These observations are incompatible with a cnidarian interpretation, in which the spaces between cross walls are abandoned parts of the former living positions of the polyp.

View Article: PubMed Central - PubMed

Affiliation: School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK Department of Palaeobiology and Nordic Center for Earth Evolution, Swedish Museum of Natural History, Stockholm 10405, Sweden john.cunningham@bristol.ac.uk.

No MeSH data available.


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SRXTM images of the tubular fossil Crassitubus. (a) SRXTM surface model of Crassitubus specimen X 5328; (b) longitudinal SRXTM slice through the specimen in (a), the region in the box is enlarged in (d); (c) SRXTM surface model of the specimen in (a) showing the exterior of the specimen in the region of the structure shown in (d), note that the former positions of cross walls are visible; (d) higher magnification image of boxed region in (g) showing a nearly spherical structure composed of sub-angular objects close to the end of the tube; (e) SRXTM surface model of Crassitubus specimen X 5329; (f) SRXTM surface model of the specimen in (e) in a different orientation; (g) SRXTM slice through the specimen in (e), the boxed region is enlarged in (h); (h) higher magnification image of the boxed region in (g), arrowhead indicates a similar structure to that shown in (d). Scale bars: (a,b) 137 µm; (c) 62 µm; (d) 26 µm; (e–g) 200 µm; (h) 50 µm. (Online version in colour.)
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RSPB20151169F3: SRXTM images of the tubular fossil Crassitubus. (a) SRXTM surface model of Crassitubus specimen X 5328; (b) longitudinal SRXTM slice through the specimen in (a), the region in the box is enlarged in (d); (c) SRXTM surface model of the specimen in (a) showing the exterior of the specimen in the region of the structure shown in (d), note that the former positions of cross walls are visible; (d) higher magnification image of boxed region in (g) showing a nearly spherical structure composed of sub-angular objects close to the end of the tube; (e) SRXTM surface model of Crassitubus specimen X 5329; (f) SRXTM surface model of the specimen in (e) in a different orientation; (g) SRXTM slice through the specimen in (e), the boxed region is enlarged in (h); (h) higher magnification image of the boxed region in (g), arrowhead indicates a similar structure to that shown in (d). Scale bars: (a,b) 137 µm; (c) 62 µm; (d) 26 µm; (e–g) 200 µm; (h) 50 µm. (Online version in colour.)

Mentions: Crassitubus is characterized by its curved, non-branching form as well as by an enveloping sheath that bears a longitudinal ridge (figure 3). Our data show that some specimens have at least two longitudinal ridges, rather than the single ridge seen in previously described material (figure 3e). Like Ramitubus, Crassitubus frequently exhibits evidence of organic decay and ductile deformation, and can be twisted and knotted [25]. There is no evidence of brittle fracture. In one of the specimens, there is an ovoid structure at one end of the tube that measures approximately 100 µm in the maximum dimension (figure 3a–d). It is composed of facetted structures that are up to 5 µm in diameter and that in some instances are organized into diads or tetrads, suggesting that they were formed by division. For these reasons, we interpret the structures as cellular compartments. It is possible that this is a coincidental, and not a biological, association between the cellular clusters and the Crassitubus organism, particularly as no internal cross walls are visible in this specimen, suggesting that it might be poorly preserved. The original positions of cross walls are visible on the outside of the specimen, both in the region of the cluster (figure 3c) and elsewhere. These walls must have been incomplete if they were to have allowed space for the cell cluster (such a pattern of cross walls is seen in fig. 2d of [19]). However, the presence of a similar structure in the same position of a second Crassitubus specimen (figure 3e–h, arrowhead in figure 3h) gives some weight to the argument that the structures are part of the organism's biology.Figure 3.


Critical appraisal of tubular putative eumetazoans from the Ediacaran Weng'an Doushantuo biota.

Cunningham JA, Vargas K, Pengju L, Belivanova V, Marone F, Martínez-Pérez C, Guizar-Sicairos M, Holler M, Bengtson S, Donoghue PC - Proc. Biol. Sci. (2015)

SRXTM images of the tubular fossil Crassitubus. (a) SRXTM surface model of Crassitubus specimen X 5328; (b) longitudinal SRXTM slice through the specimen in (a), the region in the box is enlarged in (d); (c) SRXTM surface model of the specimen in (a) showing the exterior of the specimen in the region of the structure shown in (d), note that the former positions of cross walls are visible; (d) higher magnification image of boxed region in (g) showing a nearly spherical structure composed of sub-angular objects close to the end of the tube; (e) SRXTM surface model of Crassitubus specimen X 5329; (f) SRXTM surface model of the specimen in (e) in a different orientation; (g) SRXTM slice through the specimen in (e), the boxed region is enlarged in (h); (h) higher magnification image of the boxed region in (g), arrowhead indicates a similar structure to that shown in (d). Scale bars: (a,b) 137 µm; (c) 62 µm; (d) 26 µm; (e–g) 200 µm; (h) 50 µm. (Online version in colour.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4528530&req=5

RSPB20151169F3: SRXTM images of the tubular fossil Crassitubus. (a) SRXTM surface model of Crassitubus specimen X 5328; (b) longitudinal SRXTM slice through the specimen in (a), the region in the box is enlarged in (d); (c) SRXTM surface model of the specimen in (a) showing the exterior of the specimen in the region of the structure shown in (d), note that the former positions of cross walls are visible; (d) higher magnification image of boxed region in (g) showing a nearly spherical structure composed of sub-angular objects close to the end of the tube; (e) SRXTM surface model of Crassitubus specimen X 5329; (f) SRXTM surface model of the specimen in (e) in a different orientation; (g) SRXTM slice through the specimen in (e), the boxed region is enlarged in (h); (h) higher magnification image of the boxed region in (g), arrowhead indicates a similar structure to that shown in (d). Scale bars: (a,b) 137 µm; (c) 62 µm; (d) 26 µm; (e–g) 200 µm; (h) 50 µm. (Online version in colour.)
Mentions: Crassitubus is characterized by its curved, non-branching form as well as by an enveloping sheath that bears a longitudinal ridge (figure 3). Our data show that some specimens have at least two longitudinal ridges, rather than the single ridge seen in previously described material (figure 3e). Like Ramitubus, Crassitubus frequently exhibits evidence of organic decay and ductile deformation, and can be twisted and knotted [25]. There is no evidence of brittle fracture. In one of the specimens, there is an ovoid structure at one end of the tube that measures approximately 100 µm in the maximum dimension (figure 3a–d). It is composed of facetted structures that are up to 5 µm in diameter and that in some instances are organized into diads or tetrads, suggesting that they were formed by division. For these reasons, we interpret the structures as cellular compartments. It is possible that this is a coincidental, and not a biological, association between the cellular clusters and the Crassitubus organism, particularly as no internal cross walls are visible in this specimen, suggesting that it might be poorly preserved. The original positions of cross walls are visible on the outside of the specimen, both in the region of the cluster (figure 3c) and elsewhere. These walls must have been incomplete if they were to have allowed space for the cell cluster (such a pattern of cross walls is seen in fig. 2d of [19]). However, the presence of a similar structure in the same position of a second Crassitubus specimen (figure 3e–h, arrowhead in figure 3h) gives some weight to the argument that the structures are part of the organism's biology.Figure 3.

Bottom Line: Ramitubus and Crassitubus specimens preserve enigmatic cellular clusters at terminal positions in the tubes.Specimens of Sinocyclocyclicus and Ramitubus have biological features that might be cellular tissue or subcellular structures filling the spaces between the cross walls.These observations are incompatible with a cnidarian interpretation, in which the spaces between cross walls are abandoned parts of the former living positions of the polyp.

View Article: PubMed Central - PubMed

Affiliation: School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK Department of Palaeobiology and Nordic Center for Earth Evolution, Swedish Museum of Natural History, Stockholm 10405, Sweden john.cunningham@bristol.ac.uk.

No MeSH data available.


Related in: MedlinePlus