Fossil Melanosomes Appear to be Real

Fossil melanosomes or bacteria? A wealth of findings favours melanosomes

Author:

Vinther

Abstract:

The discovery of fossil melanosomes has resulted in a wealth of research over the last 7 years, notably the reconstruction of colour in dinosaurs and fossil mammals. In spite of these discoveries some authors persist in arguing that the observed microbodies could represent preserved bacteria. They contend that bacteria fossilise easily and everywhere, which means that one can never be certain that a microbody is a melanosome without an extraordinary burden of evidence. However, this critique mischaracterises the morphological and structural evidence for interpreting microbodies as fossil melanosomes, and hence the basis for using them in reconstructing prehistoric colours. The claims for bacterial omnipresence in the fossil record are themselves not supported, thus tipping the scales strongly towards melanosomes in the bacteria-versus-melanosome controversy.

What Color Were Those Eocene Bats in the Fossils?

What colour were the animals that roamed the Earth 50 million years ago? For the first time, the original colour of a fossil mammal has been described by scientists from the University of Bristol, UK and Virginia Polytechnic Institute and State University, US.

The researchers combined morphological, experimental and chemical techniques to determine the colour of two species of bat, which lived in the Eocene Epoch, 56-33.9 million years ago.

By studying microscopic spherical and oblong-shaped structures in the fossils, they found that the bats were reddish-brown in colour. For years, scientists have been divided on whether these structures are melanosomes -organelles (subunits within in cell) that contain melanin and have distinct shapes in modern animals, which can be used to infer colour - or fossilised bacteria, which had eaten away at an animal before it was buried.

In this new study, Bristol-based Dr Jakob Vinther and Masters student Caitlin Colleary, now a PhD student at Virginia Tech, along with researchers from UT Austin and a number of other universities, show that the organic microbodies in the skin, hair, feathers and eyes of exceptionally preserved fossils (ranging in age from the Carboniferous to the Miocene, 300-20 million years ago) contain the remnants of melanin.

In order to identify the origin of these curious structures, the researchers replicated the conditions under which the fossils formed using high pressure, high temperature autoclave experiments. They showed that the fossils contain fossilised melanin by using Time-of-flight secondary ion mass spectroscopy (TOF-SIMS), which had changed in chemical composition over time.

Dr Vinther, who first described fossil melanosomes and reconstructed the colours of a feathered dinosaur, said: "This is a great leap forward in our understanding of how fossils are preserved. We now know how melanin is preserved and we have the methods to confidently detect it."

Melanin comes in two distinct colours: reddish brown phaeomelanin and black eumelanin.

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How Dark is Your Santonian Cretaceous Mosasaur? Your Sinemurian Jurassic Ichthyosaur?

Unique finds of original pigment in fossilised skin from three multi-million-year old marine reptiles attract considerable attention from the scientific community. The pigment reveals that these animals were, at least partially, dark-coloured in life, which is likely to have contributed to more efficient thermoregulation, as well as providing means for camouflage and UV protection. Researchers at Lund University are among the scientists that made the spectacular discovery.

During the Age of the dinosaurs, huge reptiles, such as mosasaurs and ichthyosaurs, ruled the seas. Previously, scientists could only guess what colours these spectacular animals had; however, pigment preserved in fossilised skin has now been analysed at SP Technical Research Institute of Sweden and MAX IV Laboratory, Lund University, Sweden. The unique soft tissue remains were obtained from a 55 million-year-old leatherback turtle, an 85 million-year-old mosasaur and a 196 million-year-old ichthyosaur. This is the first time that the colour scheme of any extinct marine animal has been revealed.

"This is fantastic! When I started studying at Lund University in 1993, the film Jurassic Park had just been released, and that was one of the main reasons why I got interested in biology and palaeontology. Then, 20 years ago, it was unthinkable that we would ever find biological remains from animals that have been extinct for many millions of years, but now we are there and I am proud to be a part of it", said Johan Lindgren about the discovery of the ancient pigment molecules.

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