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. 2015 Aug 4;5:12802.
doi: 10.1038/srep12802.

When a 520 Million-Year-Old Chengjiang Fossil Meets a Modern micro-CT--a Case Study

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Free PMC article

When a 520 Million-Year-Old Chengjiang Fossil Meets a Modern micro-CT--a Case Study

Yu Liu et al. Sci Rep. .
Free PMC article

Abstract

The 520 million-year-old Chengjiang biota of China (UNESCO World Heritage) presents the earliest known evidence of the so-called Cambrian Explosion. Studies, however, have mainly been limited to the information exposed on the surface of the slabs. Thus far, structures preserved inside the slabs were accessed by careful removal of the matrix, in many cases with the unfortunate sacrifice of some "less important" structures, which destroys elements of exceptionally preserved specimens. Here, we show for the first time that microtomography (micro-CT) can reveal structures situated inside a Chengjiang fossil slab without causing any damage. In the present study a trilobitomorph arthropod (Xandarella spectaculum) can be reliably identified only with the application of micro-CT. We propose that this technique is an important tool for studying three-dimensionally preserved Chengjiang fossils and, most likely, also those from other biota with a comparable type of preservation, specifically similar iron concentrations.

Figures

Figure 1
Figure 1. Overview of the specimen (YKLP 11086).
(a) Light microscopy (macrophotography); (b) Fluorescence microscopy. Abbreviations: an, antenna; en, endopod; ex, exopod; ey, eye; hs, head shield; p8–17, post-antennal segments; en/ex1–17, endopod/exopod of post-antennal appendages. Overall length of the specimen from head to tail 24 mm, with antennae 32 mm. Scale bars, 5 mm. Photographs in a, b taken by Y.L.
Figure 2
Figure 2. Micro-CT set-up and fine details revealed on the surface of the slab.
(a) The slab was placed as close to the X-ray source as possible to obtain the highest possible resolution in the final micro-CT images. The slab was rotated 360° during the process of scan, with a rotation radius of 42.5 mm. In this study, the anterior (Figs 2b and 3) and posterior (Fig. 4) parts of the specimen were scanned separately. (b) Fine details in the anterior part of the specimen revealed with micro-CT (volume rendering, Amira). Annulation of the antennae (an) is evident. The first post-antennal appendage (1) is uniramous and appears annulated. Exopod (ex) and endopod (en) of the 2nd to 4th post-antennal appendages are now clearly displayed. Elongated podomeres (white arrowheads) in the endopod of the 5th and 6th post-antennal appendages are shown. The blue dashed line marks a small region of the head shield, which was preserved in a flipped-over manner (blue arrow). The white dashed line indicates that the two parts of the head shield were torn apart from each other. (c) Close-up (Hires mode in Drishti) of the exopod shows a series of setae (arrowheads) at the distal end of the 3rd post-antennal appendage. Each seta is around 100 μm in length. Abbreviations as in Fig. 1. Scale bars, 2 mm in b, 1 mm in c. Photographs in a, b taken by G.S., in c by Y.L.
Figure 3
Figure 3. Fine details revealed inside the slab.
(a) Overview of the main part of the specimen. Micro-CT (Hires mode, i.e. high-resolution mode, Drishti) reveals the lateral margin (blue arrowhead) of the head shield. The annulation of the antennae is more clearly shown here than with light or fluorescence microscopy (cf. Fig. 1). The pleura of several consecutive segments (white arrowhead), and an opening (yellow arrowhead) and a fissure (red arrowhead) in the head shield were revealed. The white arrow indicates the angle from b. (b) 90°-rotated anterior part of the specimen shown in a (Hires mode, Drishti). The red dashed line indicates the surface of the specimen. The greatest depth of the lateral margin of the head shield (blue arrowhead) is 0.89 mm, that of the opening (yellow arrowhead) is 0.8 mm, the fissure (red arrowhead) 1.2 mm, and the pleurae (white arrowhead) 0.94 mm. (c) Close-up (volume rendering, Amira) of one side of the head shield from a showing an opening (yellow arrowhead) with a fissure (red arrowhead) extending towards the lateral margin (blue arrowhead) of the head shield; (d) Close-up (volume rendering, Amira) of the eighth to tenth post-antennal segments (p8–p10) indicated by their respective pleura (white arrowheads). Abbreviations as in Fig. 1. Scale bars, 2 mm. Photographs in in a, b taken by Y.L. and in c, d taken by G.S.
Figure 4
Figure 4. Fine details revealed in the posterior part of the specimen.
(a) Overview of the posterior part of the specimen. Micro-CT (Hires mode, Drishti) reveals pleurae from the right (green arrowheads) and left (white arrowheads; p8–p10) sides of the body. Two appendages (magenta arrowheads) are also visible. The white arrow indicates the viewing angle from b. (b) Posterior view of the posterior part of the specimen shown in a. The two appendages (magenta arrowheads) are located between the right and left (p8–p10) pleurae. While the right pleurae were preserved on the surface of the slab, the appendages (magenta arrowheads) and the left pleurae of the 9th to 11th post-antennal segments (p8–p10) were inside the slab. Abbreviations as in Fig. 1. Scale bars, 2 mm. Photographs in a, b taken by Y.L.

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References

    1. Chengjiang fossil site. http://whc.unesco.org/en/list/1388 (UNESCO World Heritage Centre) (2012).
    1. Hou X. et al. The Cambrian fossils of Chengjiang, China (Blackwell, 2004).
    1. Levinton J. S. The Cambrian explosion: How do we use the evidence? Biosci. 58, 855–864 (2008).
    1. Haug J. T., Waloszek D., Maas A., Liu Y. & Haug C. Functional morphology, ontogeny and evolution of mantis shrimp-like predators in the Cambrian. Palaeontology 55, 369–399 (2012).
    1. Liu Y. et al. A 520 million-year-old chelicerate larva. Nat. Commun. 5, art. 4440 (2014). - PubMed

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