Ichnological evidence for meiofaunal bilaterians from the terminal Ediacaran and earliest Cambrian of Brazil
Authors: Luke A. Parry, Paulo C. Boggiani, Daniel J. Condon, Russell J. Garwood, Juliana de M. Leme, Duncan McIlroy, Martin D. Brasier, Ricardo Trindade, Ginaldo A. C. Campanha, Mírian L. A. F. Pacheco, Cleber Q. C. Diniz, Alexander G. Liu
Journal: Nature Ecology & Evolution
Publication Date: 11 September, 2017
Department of: Earth and Environmental Sciences
Half-a-billion year old fossil burrows shed new light on animal evolution
Recently discovered traces of life more than half-a-billion years old could change the way we think about how all animals evolved on earth. A key event in life history is the transition between the Ediacaran and Cambrian geological periods, ~541 million years ago. The fossil record suggests that most major living animal groups appeared during a brief interval of time called the Cambrian Explosion. Independent lines of evidence – estimates based on the DNA of these groups, and chemical signals from the rock record – suggest animals had their origins tens of millions of years earlier than observed in the fossil record. This idea is supported by the findings of an international team, including palaeontologists from The University of Manchester, who have described a new set of fossilised burrows left by some of the first ever organisms capable of active movement. These Brazilian trace fossils measure from under 50 to 600 micrometres in diameter, and are approximately 550 million years old. They are described through high resolution CT scanning, and aged using radiometric dating. Their shape suggests these traces were created by small roundworm-like animals that used undulating locomotion to move through the sediment: the oldest known fossil evidence for bilaterally symmetrical animals. The discovery opens a hitherto unexplored window for tracking animal evolution in deep time.
- The fossil record suggests most major animal groups appeared over a geologically short time period, some 541 million years ago.
- Other lines of evidence suggest a longer, cryptic history for animal life, with earlier origin of these groups.
- New trace fossils, described with high resolution CT and aged using radiometric dating, demonstrate that animals capable of burrowing had probably evolved by 550 million years ago.
- This could reconcile the fossil record with other lines of evidence: early animal evolution could have occurred in minute organisms which are unlikely to be preserved as fossils.
- The Interdisciplinary Centre for Ancient Life, University of Manchester
- Department of Earth Sciences, Natural History Museum
- Department of Earth Sciences, University of Cambridge
- Department of Biology. Federal University of São Carlos
- Departamento de Geofisica, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo
- Department of Earth Sciences, University of Oxford
- Department of Earth Sciences, Memorial University of Newfoundland
- NERC Isotope Geosciences Laboratory, British Geological Survey
- Instituto de Geociências, Universidade de São Paulo
- Palaeobiology, Royal Ontario Museum