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The first vertebrates with a mineralized skeleton were fish without armored jaws like Anglaspis heintzi, a heterostracan who lived about 419 million years ago.
Wikimedia Image (CC BY-SA 4.0)
A fossil heterostracan, Errivaspis waynensis, early Devonian (about 419 million years ago) from Herefordshire, UK.
Image from Keating et al. 2018
Scientists from the University of Manchester and the University of Bristol used powerful X-rays to scan the skeletons of some of our oldest parents, solving a 160-year-old mystery about the origin of our skeletons. 19659004] Living vertebrates have skeletons constructed from four different tissue types: bone and cartilage (the main tissues of which human skeletons are made), and dentin and enamel (the tissues from which our teeth are built). These fabrics are unique because they mineralize as they develop, giving the skeleton strength and rigidity.
Evidence of the early evolution of our skeletons can be found in a group of fossil fish called heterostraceans, who lived more than 400 million years ago. These fish include some of the oldest vertebrates with a mineralized skeleton that have already been discovered. Exactly what tissues of heterostructured skeletons have been made from long time intrigued scientists.
A team of researchers from the University of Manchester, Bristol University and the Paul Scherrer Institute in Switzerland extensively studied the skeletons of heterostracents at the University of Manchester. Synchrotron tomography: a special type of computed tomography using very high energy X-rays produced by a particle accelerator. Using this technique, the team has identified this mysterious fabric.
Dr. Joseph Keating, a senior researcher at the University of Manchester, explained, "The heterostracial skeletons are made of a really strange tissue called 'aspidine'. It is crisscrossed by tiny tubes and is unlike any of the tissues found in vertebrates today. For 160 years, scientists have wondered if aspidine is a transient stage in the evolution of mineralized tissue.
The results of this study, published in Nature Ecology and Evolution, show that the tiny tubes are voids that originally housed fibers. These results allowed Dr. Keating to rule out all badumptions about tissue identity except one: Aspidine is the first evidence of the existence of bone in the archives fossils
. The co-author, Professor Phil Donoghue of the School of Earth Sciences at the University of Bristol, added: "These results change our perspective on the evolution of the skeleton. once thought that aspirin was the precursor of the mineralized tissues of vertebrates.We show that it is, in fact, one type of bone, and that all these tissues have had to evolve for millions of years. "
