The 2005 Clarke Memorial Lecture & 1138th General Monthly Meeting

"The quickening: beginning of animal life on Earth"

Professor Patricia Vickers-Rich, Monash University

Wednesday 7 September 2005, 6 pm for 6.30
Conference Room 1, Darlington Centre, University of Sydney

ABSTRACT

Four places in the world have yielded a most spectacular record of animal life prior to the time when shells and skeletons appeared - all of late Precambrian age, the time from around 700 to around 542 million years ago. Those places are the White Sea (as well as Siberia and the Urals) of Russia, Namibia in Southwest Africa, Newfoundland in Canada and the Flinders Ranges of South Australia. The relationships of each of these animals found in disjunct locales are and have been under debate since the early 1900's when they were first found in Africa. These first metazoans represent the lengthy fuse that was alight well before the rather misnamed 'Cambrian Explosion' to place and clearly illustrate experimentation in body plans, lifestyles and occupation of much of the marine ecospace was well underway long before 542 million years ago, when many different animal groups began digging trenches in search of food and protection, put on armour for a number of reasons and a great biodiversification event seems to have taken place - but in many ways it is just an illusion.

BIOGRAPHICAL NOTES

Patricia Vickers-Rich holds a Personal Chair in Palaeontology at Monash University in Melbourne and founded the Monash Science Centre in 1993. She received her BA from UC Berkeley and her MA and PhD from Columbia University, New York. Her early work was on the origin and evolution of the Australiasian avifauna, then later on polar faunas from the Mesozoic of Australia. She now leads an International Geological Correlation Programme investigating the biotic, climatic and geographic changes of the late Precambrian globally. Her current field work is centred in Namibia, northern Russia and Siberia.

Report on the General Monthly Meeting by Jak Kelly

After a concise introduction to the basic geological periods and the terminology Professor Patricia Vickers-Rich spoke of her work, and that of her associates, on fossils of animals in the time before the emergence of creatures with hard shells and skeletons appeared on earth in the late Precambrian. She illustrated the talk with fascinating photographs and anecdotes from her field trips to Siberia to obtain fossil remains and fossil surface trails of these earlier creatures. Some of the fossils show the internal structures of animals and some the outside, which complicates interpretation. They are also found in Namibia in Southwest Africa, in Newfoundland in Canada and the Flinders Ranges of South Australia, the world then being a single supercontinent. Strange bead like structures from WA, which at 1.66 billion years old may be the most ancient metazoans yet found, but there is still dispute about them being plant or animal. The more recent metazoans, true animals, are marine, some fixed in position and some able to move and graze. Some of the trails along which they grazed have been preserved in the fossil record. Oxygen isotope measurements reveal that the water was cold at this time. The colder the water the more oxygen it can dissolve, which was probably an advantage for the development of these animals.

An interesting aim of this field is to explain the so-called 'Cambrian Explosion', when a host of different animals appear in the fossil record over a (geologically) short time. It is easier to understand sudden mass extinctions, due perhaps to an asteroid strike, than the sudden emergence of many complicated new life forms. Some of the earlier soft shelled animals, that were the subject of this talk, have body plans like later Cambrian forms. The implication is that their soft bodies didn't fossilise as easily as the hard shelled, or with teeth and bones, descendents of those of them that survived into the Cambrian. The explosion of metazoan life, some 542 million years ago is hence probably an artefact of the fossil making processes rather than a sudden "explosion" of new life forms.

After many questions and additional discussion from the floor a vote of thanks was moved by Karina Kelly and Prof. Vickers-Rich was presented with the Society's Speaker's medal.

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