̽��ֱ�� of Cambridge - Jennifer Clack

Fossil skull sheds new light on transition from water to land

fpjl2 — Mon, 16 Mar 2015 11:18:28 +0000

A new 3D reconstruction of skull of one of the earliest four-footed vertebrate – which differs from earlier 2D reconstructions – suggests such creatures, which lived their lives primarily in shallow water environments, were more like modern crocodiles than previously thought.

̽��ֱ��researchers applied high-resolution X-ray computed tomography (CT) scanning to several specimens of Acanthostega gunnari, one of the ‘four-footed’ vertebrates known as tetrapods which invaded the land during one of the great evolutionary transitions in Earth’s history, 380-360 million years ago. Tetrapods evolved from lobe-finned fishes and display a number of adaptations to help them survive on land.

An iconic fossil species, Acanthostega gunnari is crucial for understanding the anatomy and ecology of the earliest tetrapods. However, after hundreds of millions of years in the ground fossils are often damaged and deformed. No single specimen of Acanthostega preserves a skull that is complete and three-dimensional which has limited scientists’ understanding of how this key animal fed and breathed – until now.

Researchers from Cambridge and Bristol ̽��ֱ�� used specialist software to ‘digitally prepared’ a number of Acanthostega specimens from East Greenland, stripping away layers of rock to reveal the underlying bones.

They uncovered a number of bones deep within the skull, including some that had never before been seen or described, resulting in a detailed anatomical description of the Acanthostega skull.

Once all of the bones and teeth were digitally separated from each other, cracks were repaired and missing elements duplicated. Bones could then be manipulated individually in 3D space. Using information from other specimens, the bones were fitted together like puzzle pieces to produce the first 3D reconstruction of the skull of Acanthostega, with surprising results.

Co-author Dr Laura Porro, formerly of Cambridge’s Department of Zoology and Bristol’s School of Earth Sciences (now at the Royal Veterinary College) said: “Because early tetrapods skulls are often ‘pancaked’ during the fossilization process, these animals are usually reconstructed having very flat heads. Our new reconstruction suggests the skull of Acanthostega was taller and somewhat narrower than previously interpreted, more similar to the skull of a modern crocodile.”

̽��ֱ��researchers also found clues to how Acanthostega fed. ̽��ֱ��size and distribution of its teeth and the shape of contacts between individual bones of the skull (called sutures) suggest Acanthostega may have initially seized prey at the front of its jaws using its large front teeth and hook-shaped lower jaw.

̽��ֱ��team say that these new analyses provide fresh clues about the evolution of the jaws and feeding system as the earliest animals with limbs and digits began to conquer the land.

̽��ֱ��researchers plan to apply these methods to other flattened fossils of the earliest tetrapods to better understand how these early animals modified their bones and teeth to meet the challenges of living on land.

“This work is the first stage of a study towards understanding how the earliest tetrapods fed, and that might lead us to what they fed on, and give further clues as to when and how they started to feed on land,” said co-author Professor Jennifer Clack from Cambridge’s Zoology Department.

Digital models of the original fossils and the 3D reconstruction are also useful in scientific research and education. They can be accessed by researchers around the world, without risking damage to fragile original fossils and without scientists having to travel thousands of miles to see original specimens. Furthermore, digital models and 3D printouts can be easily and safely handled by students taking courses and by the public during outreach events. ̽��ֱ��study is published recently in the journal PLOS ONE.

Adapted from a Bristol ̽��ֱ�� press release.

Inset image: 3D model showing the complete skull on top with ‘exploded’ views of the upper and lower jaws below.

̽��ֱ��first 3D reconstruction of the skull of a 360 million-year-old near-ancestor of land vertebrates has been created by scientists.

This work is the first stage of a study towards understanding how the earliest tetrapods fed, and that might lead us to what they fed on

Jennifer Clack

Porro/Clack

Left: 3D model with the jaws open; the individual bones are colour-coded to show the boundaries between them. Right: Original fossil skull of Acanthostega gunnari

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Yes

Cambridge academics elected as Fellows of the Royal Society

bjb42 — Fri, 15 May 2009 00:00:00 +0000

̽��ֱ��new Fellows, elected for their scientific excellence, are:

Professor Ross Anderson is the Professor of Security Engineering at the Computer Laboratory. Professor Anderson is a pioneer and world leader in security engineering, and is distinguished for starting a number of new areas of research in hardware, software and systems. His early work on how systems fail established a base of empirical evidence for building threat models for a wide range of applications from banking to healthcare. He has made trailblazing contributions that helped establish a number of new research topics, including security usability, hardware tamper-resistance, information hiding, and the analysis of application programming interfaces. He is also one of the founders of the study of information security economics, which not only illuminates where the most effective attacks and defences may be found, but is also of fundamental importance to making policy for the information society.

Professor Jennifer Clack is Professor and Curator of Vertebrate Palaeontology in the Museum of Zoology. Professor Clack is a palaeontologist whose work has fundamentally changed our understanding of the origin and early evolution of tetrapods, rewriting the textbooks and revitalising the subject area. Ranging from geology through phylogenetics, anatomy and development to neuroscience, her publications document the transition from fish to tetrapods. She led the field in showing that the earliest tetrapods were aquatic and polydactylous, in describing some of the earliest terrestrial tetrapods and in tracing the subsequent evolution of skeletal and sensory systems. Her work has stimulated worldwide interest and a renaissance of collecting and research related to the fish/tetrapod transition. In 2007, Professor Clack's work was recognised by the award of the Daniel Giraud Elliot medal of the US National Academy of Sciences

Professor David Glover is the Arthur Balfour Professor of Genetics in the Department of Genetics and a Fellow of Fitzwilliam College. Professor Glover is principally known for his work in the control of the cell cycle in Drosophila. Amongst the many genes discovered by his lab are those encoding the Polo and Aurora protein kinases that are required for progression through mitosis. Glover has documented the multiple roles played by these enzymes in mitosis and cytokinesis and has helped to develop small molecule inhibitors that may prove useful for cancer therapy, since these proteins are overexpressed in certain tumours. As a postdoctoral fellow in Stanford, Glover was one of the pioneers of cloning eukaryotic DNA in bacterial vectors, and discovered the presence of introns in the ribosomal RNA genes of Drosophila.

Professor Christine Holt, a Fellow of Gonville and Caius College, is Professor of Developmental Neuroscience in the Department of Physiology, Development and Neuroscience. Professor Holt is distinguished for her fundamental studies of axon guidance and topographic mapping in the visual system. She initiated the analysis of guidance and mapping in living embryos. She demonstrated the accurate targeting of the earliest retinal axons, and pioneered the dynamic imaging of axons and growth cones. She revealed the molecular basis of pathway choice at the chiasm, demonstrated the context dependent response of growth cones to guidance molecules and showed that local protein synthesis and degradation are essential to growth cone steering. She has identified the molecular basis for the dorso-ventral axis of Sperry's retinotectal map.

Professor David Mackay, a Fellow of Darwin College, is Professor of Natural Philosophy in the Department of Physics. Professor MacKay introduced more efficient types of error-correcting code that are now used in satellite communications, digital broadcasting and magnetic recording. He advanced the field of Machine Learning by providing a sound Bayesian foundation for artificial neural networks. Using this foundation, he significantly improved their performance, allowing them to be used for designing new types of steel that are now used in power stations. He used his expertise in information theory to design a widely-used interface called "dasher" that allows disabled people to write efficiently using a single finger or head-mounted pointer. He is the author of the critically acclaimed book, "Sustainable Energy - without the hot air", which sets out the various low-carbon energy options open to us.

Professor Wolfram Schultz, a Fellow of Churchill College, is Professor of Neuroscience in the Department of Physiology, Development and Neuroscience and Wellcome Trust Principal Research Fellow. He has been the most influential electrophysiologist working in the area of the reward and reinforcement in the last decade. He discovered that dopamine activity, rather than being directly related to movement, is driven by rewards and reward predicting stimuli. Moreover, he has established that the profile of activity in a variety of behavioural paradigms demonstrates that the dopamine neurons encode not simply the occurrence of the reward but rather the prediction error generated by the reward. This important finding has had a major impact on contemporary theories of learning and reinforcement. His more recent work suggests that dopamine activity may also encode an aggregate signal of reward magnitude and probability, thereby providing a critical input into economic decision processes.

Professor Henning Sirringhaus, a Fellow of Churchill College, is the Hitachi Professor of Electron Device Physics in the Department of Physics. Henning Sirringhaus is distinguished for his work on semiconductor device physics and engineering. Early in his career, at the ETH Zurich, he pioneered the technique of ballistic electron emission microscopy. At Cambridge he has transformed the field of organic semiconductor transistors from curiosity to fully manufacturable technology through both fundamental science and engineering. His insights into the polaronic nature of electron states in these materials and the control of interfacial structure made possible large increases in field-effect carrier mobility. His work on novel processing methods, including ink-jet printing, has made possible new manufacturing methods. A recent highlight is his realisation of a light-emitting field-effect transistor.

Professor John Todd, a Fellow of Gonville and Caius, is Professor of Medical Genetics at Cambridge ̽��ֱ�� and Director of the Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory in the Cambridge Institute for Medical Research. Todd is distinguished for his research on the genetics of common complex disease. In work spanning 20 years, he has pioneered theoretical and experimental approaches that have allowed him to resolve many aspects of the inheritance of type 1 diabetes. His elucidation of the molecular basis of the major gene effect in type 1 diabetes, together with his results from genome-wide analyses, have recently culminated in his successful dissection of the genetic architecture of type 1 diabetes, revealing a multiplicity of susceptibility genes converging on an aetiology of common, quantitative alterations in immune regulation.

Professor Burt Totaro is Lowndean Professor of Astronomy and Geometry in the Department of Pure Mathematics and Mathematical Statistics. ̽��ֱ��central part of Burt Totaro's work has been devoted to the interaction between two of the major areas of pure mathematics, topology and algebraic geometry. Inspired by the Hodge conjecture, Totaro has worked to unc

over the fundamental topological structure of algebraic geometry. Each step has made possible the solution of a well-known problem in algebraic geometry and demonstrated that progress towards the Hodge conjecture will come through topology. Totaro's work has influenced a large group of algebraic geometers to use deeper topological methods in their work. His ideas have also had unexpected payoffs in a wide variety of other mathematical fields, including representation theory, Lie groups and group cohomology.

Nine of the 44 new Royal Society Fellows announced today are Cambridge academics. Their election to the Fellowship of the Royal Society recognises their exceptional contributions to society. As Fellows of the UK's national academy of science, these leaders in the fields of science, engineering and medicine join other famous Cambridge names such as Isaac Newton, Charles Darwin and Stephen Hawking.

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King's College Cambridge

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Yes

International award for evolution expert

ns480 — Thu, 01 May 2008 14:43:27 +0000

Over two decades ago, Professor Jennifer Clack and colleagues made a discovery in Greenland that was to overturn ideas of our evolutionary history: a 370 million-year-old tetrapod (an animal with four legs, plus fingers and toes) whose skeleton held the clues to ‘terrestriality’. This missing link and the research it generated caused a re-evaluation of when, where, how, and in what order changes occurred during the evolutionary transition from water to land. It is these important contributions to science that have recently been recognised through the awarding of the Daniel Giraud Elliot Medal to Professor Clack by the National Academy of Sciences.

‘ ̽��ֱ��transition from water- to land-dwelling creatures in the Late Devonian period is one of the major evolutionary events since it triggered the radiation of all subsequent vertebrate life on land,’ explained Professor Clack, Curator of Vertebrate Palaeontology at the ̽��ֱ��’s Department of Zoology. Professor Clack’s discoveries, including the earliest foot adapted for walking, initiated a revolution in perceptions of this key transition.

‘Limbs appear to have first evolved in water and we now know that the first four-limbed creatures possessed multiple fingers and toes rather than the architypal five,’ said Professor Clack. ‘We believe that these evolved to help propel them through weed-choked swamps.’ Her climate studies suggest that the transition to land came at a time of low oxygen in the atmosphere, and even lower in the water, when being able to breathe air became an advantage.

As a result of these detailed analyses, curators are now able to recognise similar fossils in museum collections the world over. ̽��ֱ��result is a worldwide re-evaluation of the fossil record and a resurgence of interest in the field.

Almost 150 years ago, when Charles Darwin published his theories on the origin of species, the fossil record was frustratingly incomplete, with few examples of transitional stages in evolution. Professor Clack’s research is helping to complete the story.

For more information, please contact Professor Jennifer Clack (j.a.clack@zoo.cam.ac.uk).

Professor Jennifer Clack’s research into one of the major events in the evolutionary history of life on Earth has been honoured by the National Academy of Sciences.

This missing link and the research it generated caused a re-evaluation of when, where, how, and in what order changes occurred during the evolutionary transition from water to land.

Professor Jennifer Clack

Skull of one of the earliest known animals, Acanthostega gunnari found in Greenland, 1987

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Yes