The fossil is well-preserved and the research team was able to even ascertain the hair structures and inner organs. The discovery of a 125-million-year-old fossil has revealed a furry chipmunk-sized mammal which probably went extinct around 66 million years back, said the research team. Researchers estimate that the small mammal could have weighed around 50-70 grams. The mammal was thriving on the planet during the age of dinosaurs and went extinct nearly 66 million years ago.
The rare fossil was discovered by a team led by Angela Buscalioni from the Autonomous University of Madrid, in Spain.
The fossil showcases spines similar to a hedgehog and has been linked to the times when dinosaurs thrived in the region. The research team has dubbed it as a 'cute furball'. The mammal fossil from the dinosaur era depicts a horny body armor and unpleasant fungal hair infection.
The paleontologists working on the project found the fossil in Cuenca, Spain. The fossil includes a complete skeleton with preserved fur. The mammal features rounded external ears and the research team could easily notice the skin pores and soft tissue of the liver and lungs. The team termed it as the best preserved fossil unearthed till date from the Mesozoic era. The fossil is nearly 65 million years older than the next-oldest record of microscopic structures of hair in mammal fossils.
University of Bonn paleontologist Thomas Martin said, "Yes, indeed, it is the best-preserved mammal fossil from the Mesozoic. The discovery of Spinolestes is extremely exciting for me because it provides information on structures that we believed would never be accessible."
The Spinolestes is similar to African rodent called a spiny mouse. It can be considered as a member of a primitive mammalian group called eutriconodonts that was found nearly 170 million years ago. The species went extinct around 66 million years ago. The study has been published in the journal Nature.
University of Chicago paleontologist Zhe-Xi Luo added that the fossil provides valuable information about mammals that thrived on the planet during the dinosaur age. Luo said, "It would look like small rat, except it has a more pointy nose. This extinct mammal combines all types of hairs and hair-related structures of modern mammals: long guard hairs, velvet underfur, spines and scutes."
The research team noticed abnormally truncated hairs which could be a sign of fungal infection or dermatophytosis.
The research paper said.....
The specimen, named Spinolestes xenarthrosus, was fossilized with remarkably intact guard hairs, underfur, tiny hedgehog-like spines and even evidence of a fungal hair infection. The unusually well-preserved fossil also contains an external ear lobe, soft tissues of the liver, lung and diaphragm, and plate-like structures made of keratin known as dermal scutes. The microscopic structures of hair and spines in Spinolestes are the earliest-known examples in mammalian evolutionary history.
The findings are described by scientists from the Autonomous University of Madrid, University of Bonn and the University of Chicago in a study published in Nature on Oct. 15.
"Spinolestes is a spectacular find. It is stunning to see almost perfectly preserved skin and hair structures fossilized in microscopic detail in such an old fossil," said study co-author Zhe-Xi Luo, PhD, professor of organismal biology and anatomy at the University of Chicago. "This Cretaceous furball displays the entire structural diversity of modern mammalian skin and hairs."
The Las Hoyas Quarry in east-central Spain was once a lush wetland with a thriving diversity of life around 125 million years ago during the early Cretaceous period. Spanish paleontologists have studied the site since 1985 and found hundreds of fossils, including important birds and dinosaurs. In 2011, the first mammal fossil at the site was discovered by a team led by Angela D. Buscalioni, PhD, professor of paleontology at the Autonomous University of Madrid, who partnered with collaborators including Luo and Thomas Martin, PhD, professor of paleontology at the University of Bonn, to study the rare specimen.
Spinolestes is also the first example of a Mesozoic mammal in which soft tissues in the thoracic and abdominal cavities are fossilized. The team noted microscopic bronchiole structures of the lung, as well as iron-rich residues associated with the liver. These areas were separated by a curved boundary that is thought to be a muscular diaphragm for respiration. This represents the earliest-known record of mammalian organ systems.
The fossil of Spinolestes contains a large external ear, the earliest-known example in the mammalian fossil record, as well as dermal scutes—plate-like structures made of skin keratin. A more developed form of scutes can be seen in modern armadillos and pangolins.
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