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X-ray Synchrotron Microtomography of a silicified Jurassic Cheirolepidiaceae (Conifer) cone: histology and morphology of Pararaucaria collinsonae sp. nov.

DOI: 10.7717/peerj.624 DOI Help
PMID: 25374776 PMID Help

Authors: David C. Steart (Natrual History Museum London, U.K.) , Alan R. T. Spencer (Imperial College London, U.K.) , Russell J. Garwood (University of Manchester, U.K.) , Jason Hilton (University of Birmingham, U.K.) , Martin C. Munt (Natrual History Museum London, U.K.) , John Needham (U.K.) , Paul Kenrick (Natrual History Museum London, U.K.)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Peerj , VOL 2 (624) , PAGES 2 (624)

State: Published (Approved)
Published: October 2014
Diamond Proposal Number(s): 9244

Open Access Open Access

Abstract: We document a new species of ovulate cone (Pararaucaria collinsonae) on the basis of silicified fossils from the Late Jurassic Purbeck Limestone Group of southern England (Tithonian Stage: ca. 145 million years). Our description principally relies on the anatomy of the ovuliferous scales, revealed through X-ray synchrotron microtomography (SRXMT) performed at the Diamond Light Source (UK). This study represents the first applications of SRXMT to silicified plant fossils, and demonstrates the significant advantages of this approach, which can resolve cellular structure over lab-based X-Ray computed microtomography (XMT). The method enabled us to characterize tissues and precisely demarcate their boundaries, elucidating organ shape, and thus allowing an accurate assessment of affinities. The cones are broadly spherical (ca. 1.3 cm diameter), and are structured around a central axis with helically arranged bract/scale complexes, each of which bore a single ovule. A three-lobed ovuliferous scale and ovules enclosed within pocket-forming tissue, demonstrate an affinity with Cheirolepidiaceae. Details of vascular sclerenchyma bundles, integument structure, and the number and attachment of the ovules indicate greatest similarity to P. patagonica and P. carrii. This fossil develops our understanding of the dominant tree element of the Purbeck Fossil Forest, providing the first evidence for ovulate cheirolepidiaceous cones from this locality. Alongside recent discoveries in North America, this significantly extends the known palaeogeographic range of Pararaucaria, supporting a mid-palaeolatitudinal distribution in both Gondwana and Laurasia during the Late Jurassic. Palaeoclimatic interpretations derived from contemporaneous floras, climate sensitive sediments, and general circulation climate models indicate that Pararaucaria was a constituent of low diversity floras in semi-arid Mediterranean-type environments.

Subject Areas: Earth Science, Biology and Bio-materials, Technique Development

Instruments: I12-JEEP: Joint Engineering, Environmental and Processing

Other Facilities: No

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