The Spinolestes xenarthrosus fossil was recovered from a limestone deposit near Cuenca, Spain. Photo by Bonn University/Nature
BON, Germany, Oct. 14 (UPI) -- A new study suggests a 125-million-year-old rodent fossil, recently found and remarkably well preserved, showcases of the evolutionary potential of early mammals.
The Spinolestes xenarthrosus fossil, unearthed in Spain, features the earliest-yet evidence of mammalian hair, an external ear lobe and soft tissues of the liver, lung and diaphragm.
The discovery is detailed in an online paper, published this week in the journal Nature.
"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," study co-author Zhe-Xi Luo, professor of organismal biology and anatomy at the University of Chicago, said in a press release. "This Cretaceous furball displays the entire structural diversity of modern mammalian skin and hairs."
An international team of researchers from Chicago, Germany and Spain believe the rat-like creature was quickly and neatly preserved in a process called phosphatic fossilization, whereby the decaying animal is quickly enveloped by phosphate-emitting microbes.
The process preserved hair follicles as well as a spine-like bulbs, similar to the spikes that adorn modern day porcupines.
"We are familiar with these characteristics in modern spiny mice from Africa and Asia Minor," explained Thomas Martin, a paleontologist at the University of Bonn, in Germany. "If a predator grabs them by the back, the spines detach from the skin. The mouse can escape and the attacker is left with nothing more than a mouthful of spines."
Researchers say the animal's abnormally shortened hairs suggest the presence of a fungal skin infection called dermatophytosis, common among modern mammals -- evidence that ancient animals may suffered from many of the same diseases present today.
Also unique is the creature's spine. Its interlocking appendages made it especially strong.
"Similar structures are found today in armadillos and anteaters but also in the African hero shrew," Martin said. "For instance, the hero shrew uses its strong back to break off palm fronds from the trunk of the tree. In this way, it can reach insect larvae living between the attachment points of the fronds and the trunk."
Though mammals living alongside the dinosaurs were rather small, they weren't primitive. The new findings suggest many of the evolutionary adaptations that helped mammals later flourish were already present during the early Cretaceous.