Admissions > PhD by research > Research Projects > Evolutionary assembly of the gnathostome bodyplan

Evolutionary assembly of the gnathostome bodyplan

Professor Philip Donoghue and Dr Zerina Johanson (NHM) [Possibility of NHM-CASE funding]

The origin of jawed vertebrates represents a singular event in vertebrate evolution, when all of the basic features that we consider general to vertebrates, such as the presence of a vertebral skeleton, paired appendages, a jointed gill skeleton, and jaws, first evolved. The significance of the event is well recognised throughout evolutionary biology and has been the subject of intense investigation by comparative anatomists (1) and developmental biologists (2) who have sought to explain the origin of these key vertebrate characters on the basis of changes in the genetic regulation of development. These evolutionary scenarios are derived from embryological comparisons of living lineages that sit astride the gnathostome divide - jawless lampreys and versus jawed sharks or fish. These are very remote comparisons that must be tested and informed by fossil remains of extinct intermediates that preserve a rich record of skeletal at a variety of evolutionary stages.

 Research into extinct relatives of living jawed vertebrates has not been sluggish – they have been the subject of a slew of recent papers in the journals Science and Nature. There is a vast literature on their comparative anatomy and these fossil groups have been focal in recent debates on the origin of key gnathostomes innovations such as teeth (3, 4). Unfortunately, however, no one has yet bothered to work out the sequence of evolution within most of the crucial skeletal units and so here is an opportunity for a gifted candidate to make their mark not only within the field of palaeontology, but comparative anatomy and evolutionary developmental biology as well.

 The aim of this research project, then is to uncover the sequence of evolution within a series of organs based on their skeletal remains. It will require analysis of the skeletal remains in fossil intermediates of living jawed and jawless vertebrates, namely osteostracans, placoderms and acanthodians, but also of living lampreys, sharks and bony fish as well. At the least, the project will focus on the evolution of the vertebral, gill, and fin/limb skeletons, because there are established scenarios based in developmental genetics that are available for testing. The objective for the student will be to trace the sequence of origin of gnathostome characteristics, through fossil representatives of increasingly primitive evolutionary grades, ultimately to the condition seen in lampreys. Established scenarios, which invariably predict a sequence of character evolution, will then be tested for compatibility and, inevitably, modified.

 Methods of analysis will include conventional light, and scanning electron microscopy of articulated material, including acid-preparation and analysis of exceptionally preserved material from the Late Devonian Gogo Formation of Western Australia (5). Specimens will also be subject to histological analysis, including use of X-ray microtomography.

Training

We are looking for candidates with a good grounding in palaeontology, biology or geology. The student will be provided with training in how to design and execute a research programme, as well as specialist training in the methods of advanced microscopy, tomography and the analysis of tomographic data, vertebrate comparative anatomy and phylogenetic analysis. Successful completion of the project will yield a number of substantial and significant scientific articles in international peer-reviewed journals.

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Dunkleosteus - a fearsome example of one of the earliest vertebrates with jaws

References

  1. J. Mallatt, Acta Zoologica (Stockholm) 78, 279 (1997).
  2. S. Kuratani, Journal of Anatomy 207, 489 (2005).
  3. M. M. Smith, Z. Johanson, Science 299, 1235 (2003).
  4. Z. Johanson, M. M. Smith, Biological Reviews 80, 303 (2005).
  5. J. A. Long, K. Trinajstic, Z. Johanson, Nature 457, 1124 (2009).

 

Last updated: 1/11/11