Duncan is responsible for the day-to-day management of the Museum’s mineralogy and petrology collections, and parts of the invertebrate palaeontology collections.
Storage, conservation and rationalisation of collections
Documentation, digitisation and imaging
Developing the collections through new acquisitions
Answering enquiries and facilitating research visits and loans
Developing new exhibitions and displays
His research interests are focused on: using the fossil record to understand the early evolution of animals, in particular their skeletons; how decay and preservation bias our understanding of exceptionally preserved fossils; and, the anatomy and evolution of the first vertebrates.
Duncan has an MGeol in Geology with Palaeobiology from the University of Leicester, and completed a PhD at the University of Bristol using pioneering Synchrotron Radiation X-Ray Tomographic Microscopy to reveal the internal structure of the first vertebrate and brachiopod skeletons.
Since his PhD Duncan has held a number of postdoctoral research positions, most recently as a Leverhulme Early Career Fellow at the Museum of Natural History and Junior Research Fellow at Linacre College, co-funded by the John Fell Fund.
The impact of taphonomic data on phylogenetic resolution: Helenodora inopinata (Carboniferous, Mazon Creek Lagerstätte) and the onychophoran stem lineage.
Murdock, DJE, Gabbott, SE, Purnell, MA
BMC evolutionary biology
The origin of the body plan of modern velvet worms (Onychophora) lies in the extinct lobopodians of the Palaeozoic. Helenodora inopinata, from the Mazon Creek Lagerstätte of Illinois (Francis Creek Shale, Carbondale Formation, Middle Pennsylvanian), has been proposed as an intermediate between the "weird wonders" of the Cambrian seas and modern terrestrial predatory onychophorans. The type material of H. inopinata, however, leaves much of the crucial anatomy unknown.Here we present a redescription of this taxon based on more complete material, including new details of the head and posterior portion of the trunk, informed by the results of experimental decay of extant onychophorans. H. inopinata is indeed best resolved as a stem-onychophoran, but lacks several key features of modern velvet worms including, crucially, those that would suggest a terrestrial mode of life.The presence of H. inopinata in the Carboniferous demonstrates the survival of a Cambrian marine morphotype, and a likely post-Carboniferous origin of crown-Onychophora. Our analysis also demonstrates that taphonomically informed tests of character interpretations have the potential to improve phylogenetic resolution.
Decay of velvet worms (Onychophora), and bias in the fossil record of lobopodians.
Murdock, DJ, Gabbott, SE, Mayer, G, Purnell, MA
BMC evolutionary biology
BACKGROUND:Fossil lobopodians, including animals proposed to have close affinity to modern onychophorans, are crucial to understanding the evolution of the panarthropod body plan and the phylum-level relationships between the ecdysozoan groups. Unfortunately, the key features of their anatomy are un-mineralized and subject to biases introduced during death, decay and preservation, yet the extent to which these fossils have been affected by the processes of post-mortem decay is entirely untested. Recent experimental work on chordates has highlighted a profound bias caused by decay, resulting in the erroneous interpretation of badly decayed specimens as primitive members of a clade (stemward slippage). The degree to which this bias affects organisms other than chordates is unknown. RESULTS:Here we use experimental decay of velvet worms (Onychophora) to examine the importance of decay bias in fossil lobopodians. Although we find stemward slippage is not significant in the interpretation of non-mineralized lobopodian fossils, the affect of decay is far from unbiased. Quantitative analysis reveals significant changes in body proportions during decay, a spectrum of decay resistance across anatomical features, and correlated decay of topologically associated characters. CONCLUSIONS:These results have significant implications for the interpretation of fossil lobopodian remains, demonstrating that features such as body outline and relative proportions are unreliable for taxonomy or phylogenetic reconstruction, unless decay is taken into account. Similarly, the non-independent loss of characters, due to juxtaposition in the body, during decay has the potential to bias phylogenetic analyses of non-biomineralized fossils. Our results are difficult to reconcile with interpretations of highly decay-prone tissues and structures, such as neural tissue, and complex musculature, in recently described Cambrian lobopodians. More broadly, we hypothesize that stemward slippage is unlikely to be a significant factor among the taphonomic biases that have affected organisms where decay-resistant features of the anatomy are rich in phylogenetically informative characters. Conversely, organisms which possess decay-resistant body parts but have informative characters concentrated in decay-prone tissues will be just as liable to bias as those that lack decay-resistant body parts. Further experimental analysis of decay is required to test these hypotheses.
Functional adaptation underpinned the evolutionary assembly of the earliest vertebrate skeleton.
Murdock, DJE, Rayfield, EJ, Donoghue, PCJ
Evolution & development
Conodonts are the first vertebrates to bear a mineralized skeleton, restricted to an array of tooth-like feeding elements. The functional implications for the development of tooth-like elements differentiated into two tissues is tested using 2D finite element modeling, mapping the patterns of stress and strain that elements with differing material properties exhibited during function. Addition of a stiff crown does not change the patterns of stress, rather it reduces the deformation of the element under the same force regime, and distributes stress more evenly across the element. The euconodont crown, like vertebrate dental enamel, serves to stiffen the element and protect the underlying dentine. Stiffness of the crown may be a contributing factor to the subsequent diversity of euconodont form, and logically function, by allowing a greater range of feeding strategies to be employed. The euconodont crown also serves as an analogue to enamel and enameloid, demonstrating that enamel-like tissues have evolved multiple times in independent vertebrate lineages, likely as a response to similar selective pressures. Conodonts can, therefore, serve as an independent test on hypotheses of the effect of ecology on the development of the vertebrate skeleton.