Ancient vertebrates as never seen before


Rebecca Pool

Wednesday, August 21, 2019 - 21:45
10 million-year-old fossil tadpole and X-ray map showing elevated levels of titanium in the skin, eye and especially the liver. [Valentina Rossi.]
A team of researchers from Ireland, the US and Japan have unveiled incredibly accurate depictions of ancient vertebrates after developing a new way to reconstruct the anatomy of these animals.
The team used cutting-edge synchrotron techniques to analyse the chemistry of fossilized melanosomes from internal organs, allowing them to peer inside the anatomy of the fossils and uncover hidden features.
Until recently, most studies on fossil melanin have focused on the skin and feathers, whereas here the pigment is linked to visible colour.
Unexpectedly, the new study also showed that melanin is abundant in internal organs of modern amphibians, reptiles, birds and mammals, and their fossil counterparts.
(l-r) Dr Maria McNamara and Valentina Rossi, UCC, who led the study. [Mike McSweeney/ Provision]
“This discovery is remarkable in that it opens up a new avenue for reconstructing the anatomy of ancient animals,” says Dr Maria McNamara from University Cork College. “In some of our fossils we can identify skin, lungs, the liver, the gut, the heart, and even connective tissue.”
“What’s more, this suggests that melanin had very ancient functions in regulating metal chemistry in the body going back tens, if not hundreds, of millions of years,” she adds.
The team made the initial discovery of internal melanosomes last year on fossil frogs.
“After the pilot study, we had a hunch that these features would turn out to be more widespread across vertebrates,” says UCC researcher, Valentina Rossi. “But we never guessed that the chemistry would be different in different organs.”
Rapid-scanning synchrotron-based X-ray fluorescence data were collected at the Stanford Synchrotron Radiation Lightsource using beam-line 10-2b for x-ray absorption spectroscopy imaging, x-ray diffraction/scattering.
Chemistry of preserved melanosomes in 10 million-year-old fossil frog . False colour SRS-XRF maps show Ca (red), Cu (blue), and Zn (green) in internal organs. [Natural History Museum/Valentina Rossi].
According to Rossi, the advent of new synchrotron X-ray analysis techniques has allowed the researchers to harness the energy of really fast-moving electrons to detect minute quantities of different metals in the melanosomes.
Also, their fossils have been so well-preserved that even the melanin molecule can be detected.
“Collectively, these data indicate that vertebrate melanins share fundamental physiological roles in homeostasis via the scavenging and sequestering of metals,” says Rossi. “[Data] suggest that intimate links between melanin and metal metabolism in vertebrates have deep evolutionary origins.”
Research is published in PNAS.
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