Imperial College London
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Alan R.T. Spencer

Faculty of Engineering, Department of Earth Science & Engineering

Senior Strategic Teaching Fellow
 
 
 
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Contact

 

+44 (0)20 7594 6404alan.spencer Website CV

 
 
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Location

 

2.31ARoyal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Spencer:2017:10.7717/peerj.3723,
author = {Spencer, ART and Garwood, RJ and Rees, AR and Raine, RJ and Rothwell, GW and Hollingworth, NTJ and Hilton, J},
doi = {10.7717/peerj.3723},
journal = {PeerJ},
title = {New insights into Mesozoic cycad evolution: an exploration of anatomically preserved Cycadaceae seeds from the Jurassic Oxford Clay biota},
url = {http://dx.doi.org/10.7717/peerj.3723},
volume = {5},
year = {2017}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Most knowledge concerning Mesozoic Era floras has come from compression fossils. This has been augmented in the last 20 years by rarer permineralized material showing cellular preservation. Here, we describe a new genus of anatomically preserved gymnosperm seed from the Callovian–Oxfordian (Jurassic) Oxford Clay Formation (UK), using a combination of traditional sectioning and synchrotron radiation X-ray micro-tomography (SRXMT). Oxfordiana motturii gen. et sp. nov. is large and bilaterally symmetrical. It has prominent external ribs, and has a three-layered integument comprising: a narrow outer layer of thick walled cells; a thick middle parenchymatous layer; and innermost a thin fleshy layer. The integument has a longitudinal interior groove and micropyle, enveloping a nucellus with a small pollen chamber. The large size, bilateral symmetry and integumentary groove demonstrate an affinity for the new species within the cycads. Moreover, the internal groove in extant taxa is an autapomorphy of the genus Cycas, where it facilitates seed germination. Based upon the unique seed germination mechanism shared with living species of the Cycadaceae, we conclude that O. motturii is a member of the stem-group lineage leading to Cycas after the Jurassic divergence of the Cycadaceae from other extant cycads. SRXMT—for the first time successfully applied to fossils already prepared as slides—reveals the distribution of different mineral phases within the fossil, and allows us to evaluate the taphonomy of Oxfordiana. An early pyrite phase replicates the external surfaces of individual cells, a later carbonate component infilling void spaces. The resulting taphonomic model suggests that the relatively small size of the fossils was key to their exceptional preservation, concentrating sulfate-reducing bacteria in a locally closed microenvironment and thus facilitating soft-tissue permineralization.
AU  - Spencer,ART
AU  - Garwood,RJ
AU  - Rees,AR
AU  - Raine,RJ
AU  - Rothwell,GW
AU  - Hollingworth,NTJ
AU  - Hilton,J
DO  - 10.7717/peerj.3723
PY  - 2017///
SN  - 2167-8359
TI  - New insights into Mesozoic cycad evolution: an exploration of anatomically preserved Cycadaceae seeds from the Jurassic Oxford Clay biota
T2  - PeerJ
UR  - http://dx.doi.org/10.7717/peerj.3723
UR  - https://peerj.com/
UR  - http://hdl.handle.net/10044/1/50557
VL  - 5
ER  -
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