Derek Briggs is G. Evelyn Hutchinson Professor of Geology and Geophysics at Yale University. For the special issue of Philosophical Transactions B celebrating the 350th anniversary of the journal, he has written a commentary on one of the highlights from the Philosophical Transactions archive.
The Burgess Shale has been a treasure trove for palaeontologists. Tell us a bit about it, and Harry Whittington’s work there.
The Burgess Shale is one of the those extraordinary fossil deposits where soft-bodied organisms are preserved, in contrast to the usual accumulations of shelly remains, providing an unusually complete picture of marine life in the past. Discovered in 1909 in a spectacular setting in the Canadian Rockies, it provided the first evidence of the range of creatures that evolved during the Cambrian explosion, the diversification of animal life in the oceans over 500 million years ago. Harry Whittington led the modern investigation of the Burgess Shale fossils following new excavations at the site by the Geological Survey of Canada in the 1960s.
What was Opabinia? Can it be compared to any living animals today?
Opabinia is a remarkable creature with a long proboscis-like feeding appendage on the front of its head, 5 eyes, a series of swimming flaps along the length of the body bearing filaments that functioned as gills, and an elaborate tail. Whittington published the first detailed description and reconstruction of Opabinia in 1975 but he found it difficult to classify among living forms. Opabinia looks very different to animals around today – indeed Stephen Jay Gould in his bestseller Wonderful Life called it a weird wonder!
Have any views or theories about Opabinia changed significantly since Whittington’s original paper?
Analyses of morphological information from both fossil and living animals have shown that Opabinia was not so weird – it was an early offshoot of the evolutionary lineage leading to modern arthropods, the group that includes shrimps, scorpions, spiders, millipedes and insects.
What tools did Whittington have available to him? How does that compare to now?
Whittington prepared the specimens with a modified dental drill, studied them under a microscope, photographed them and made detailed drawings as a basis for his interpretations of the Burgess Shale fossils. Such approaches remain the essential tool kit of a palaeontologist but we now have the advantage of new imaging methods, and computer programs to analyse the relationships between species.
Did you discover anything surprising whilst researching this paper?
Not really, but this was not unexpected – I was one of Harry Whittington’s graduate students while he was researching Opabinia and have been active in the field ever since.
What discoveries are happening now in this field? What single question would you like to see answered?
Many more Burgess Shale-type fossil deposits are now known, from all over the world, and new animals are continually being discovered and described. A major challenge is to determine the conditions and evolutionary processes that resulted in such a range of form in a relatively short time. This is an interdisciplinary endeavour, involving not just palaeontologists, but also geochemists, and biologists working in genetics and evolutionary development.