The partial skeletal remains of an enantiornithine bird that lived 99 million years ago (Cretaceous period) have been found preserved in a piece of amber from northern Myanmar (Burma).
The new piece of amber was found at the Angbamo site in Tanai township of Myanmar’s Kachin state.
The specimen measures 12.7 x 8.8 x 4.5 cm (5 x 3.5 x 1.8 inches) and weighs 284 g, and is the ninth reported Burmese amber specimen with bird skeletal remains.
It preserves the portions of two wings with feathers and two feet all belonging to the same individual making it one of the relatively more complete specimens known so far.
“The specimen preserves the distal portions of both wings and feet, although most of the skeletal elements are poorly preserved due to various degrees of dissolution and decay,” said Dr. Lida Xing from the China University of Geosciences and the Yingliang Stone Nature History Museum and her colleagues from China, Canada and the United States.
The researchers scanned the remains of the ancient bird with an X-ray micro-CT and compared them to previously described specimens.
“Without scanning it is impossible to view the morphology of the skeletal elements obscured both by the preservation of soft tissue and the amber itself, which includes numerous inclusions,” they noted.
By examining the wing and feet close-up, they found that the bird was a type of enantiornithine, an extinct group of dino-era toothed birds.
“Although the skeletal remains are poorly preserved, the cumulative morphological features (e.g., penultimate pedal phalanges longest, pedal ungual phalanges long and recurved) suggest referral to the Enantiornithes, the dominant group of Cretaceous land birds and so far the only group identified with certainty in Burmese amber,” they explained.
According to the team, the specimen most likely represents a juvenile, like a majority of previously described specimens from Burmese amber.
“The limb proportions differ from that of the most complete enantiornithine previously reported in amber suggesting some ecological diversity among the enantiornithines in this fauna,” the authors said.
“In this and other enantiornithine specimens the feathers are preserved with a visible brown color, suggesting this may not be indicative of in vivo coloration. Pale spots and bands are considered to be true features,” they added.
“Although obscured by preservation and other inclusions in the amber, it appears that the plumage pattern differs in all specimens uncovered so far.”
“In the future, novel chemical analyses may help to further elucidate how color patterns observed in feathers preserved within amber would actually translate to in vivo coloration.”
The study was published in the journal Frontiers in Earth Science.
Lida Xing et al. A New Enantiornithine (Aves) Preserved in Mid-Cretaceous Burmese Amber Contributes to Growing Diversity of Cretaceous Plumage Patterns. Front. Earth Sci, published online July 16, 2020; doi: 10.3389/feart.2020.00264