Researchers now know why ancient tetrapods, which resembled amphibians and lived more than 300 million years ago, appeared to have had their bones burned after passing away in one of Ireland's most significant fossil sites.
One of Ireland's most significant fossil sites, the Jarrow Assemblage contains some of the earliest amphibians to have lived on land. In Co. Kilkenny, these fossils were discovered in a coal seam.
The interior bone morphology of the fossils from this site has been changed from their original state, making it impossible to discern fine details.
Scientists are perplexed as to the reason for this transformation, which is typically attributed to acid dissolving the bones during the first burial of the animals. Up until now, that is.
In order to investigate the causes of this alteration, a team of scientists from Trinity College Dublin, University College Dublin, National University of Ireland, Galway, the University of Birmingham, and the Gemological Institute of America combined computed tomography and laser ablation to produce X-Ray images of the fossil and analyse the chemistry of the bones.
Dr. Aodhan O Gogain, from Trinity's School of Natural Sciences, is the lead author of the study. He said, "Normally in fossil bone, we see that the internal original structure is preserved. But when we looked at the X-Ray images of fossils from Jarrow we see that no internal bone morphology has been preserved and that bones have been partially replaced by the surrounding coal."
The team also found apatite preserved in the bones. Dr Gary O'Sullivan, a co-author in the study said, "The chemistry of the apatite crystals can tell us a lot about how it formed, whether it grew organically in the animal, formed when the animal was being buried or whether some other factors influenced its growth. Apatite is a major constituent of living bone so it is no surprise we find some preserved in these bones. However, when we look at the chemistry of apatite in the bones from Jarrow we find that this apatite was formed by heated fluids within the Earth
Dr Aodhan O Gogain added, "We have also been able to radiometrically date the apatite which shows it formed during a time when all the continents on Earth were coming together and colliding to form the supercontinent Pangaea. As these continents collided, they formed mountain belts with super-heated subterranean fluids flowing off them. It is these super-heated fluids, which flowed throughout Ireland that cooked and melted the bones of these fossils causing the alteration we see today."
Trinity's Dr Patrick Wyse Jackson, another co-author said, "The Jarrow assemblage is of major scientific importance and is a significant element of Ireland's geo-heritage. It is great that finally the question of what altered the fossil bones of these animals has been resolved."
( With inputs from ANI )
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