A team of researchers hailing from China, Canada, and the U.S. has recently made a remarkable discovery: mummified remains of a bird from the mid-Cretaceous period preserved in amber. This find, detailed in their paper published in Nature Communications, represents a significant milestone as it showcases the first instance of skeletal material alongside feathers encapsulated in Mesozoic amber.
The discovery took place within a small piece of amber originally unearthed in Myanmar. Within this amber fragment, the researchers identified two bird samples belonging to enantiornithines, a group of birds that perished approximately 66 million years ago, coinciding with the extinction event that wiped out the dinosaurs. Enantiornithines were characterized by possessing both teeth and wings equipped with claws on their tips. The size of the birds was diminutive, with the entire amber piece measuring just a few cubic centimeters, indicating that the specimens were likely juveniles.
Employing advanced techniques, the team meticulously analyzed the samples using microscopes and X-ray micro-computed tomography scanning. Additionally, they utilized UV light to examine the amber’s internal structure and flow patterns before solidification. This comprehensive approach revealed claw marks near one of the bird samples, suggesting a struggle to extricate itself from the sticky tree resin. Intriguingly, both birds exhibited adult-type feathers, indicating that they were born with fully developed plumage and did not undergo a molting phase.
The rarity of these findings cannot be overstated. Unlike most fossilized bird remains preserved as 2D imprints in sedimentary rock, the birds encased in amber offer genuine 3D samples that provide invaluable insights into both skeletal anatomy and feather structure within a single specimen. Furthermore, these ancient feathers retain their original hues, offering a glimpse into the coloration of these avian creatures approximately 99 million years ago—pale darks with scattered dots and deeper browns adorning various parts.
Of particular interest is the similarity in feather arrangement between these ancient birds and their modern counterparts. Despite differences in shoulder structure, the researchers posit that these birds likely flew in a manner akin to present-day avians. This finding opens a window into the transitional phase of flight evolution, bridging the gap between gliding and fully powered flight, a topic ripe for further investigation and exploration.