Plumadraco Bangkoolam, a newly identified enantiornithine bird species, inhabited what is now northeastern China during the Cretaceous period approximately 121 million years ago.

Plumadraco Bangkoolam belongs to the Enantiornithine clade, which represents the most diverse group of birds during the Cretaceous and is now extinct alongside non-avian dinosaurs.

While many enantiornithines are documented with elongated tail feathers, the proportions of this bird’s tail are unparalleled.

“Enantiornithines are the most specialized Mesozoic birds, with over 100 genera described so far, with specimens discovered on every continent except Antarctica,” stated lead author Dr. Alex Clarke, a candidate at the Field Museum and the University of Chicago.

“The extraordinary preservation of enantiornithine fossils from the Early Cretaceous Jehor biota (130 to 120 million years ago) in northeastern China typically includes soft tissue structures, predominantly feathers.”

“Contour feathers are the most abundant, followed by remiges, while tail feathers (rectrices) are relatively rare.”

Most enantiornithine specimens that preserve soft tissue lack tail feathers, only exhibiting contour feathers covering the tail—a condition not found in all extant neornithines.

Plumadraco Bangkoolam measures 14.9 cm (6 in) from beak to tail, yet its twin tail feathers extend to 29.3 cm (11.5 in).

In contrast, its closest rival, Oba junonis, achieves only about 1.6 times its body length.

“Plumadraco Bangkoolam is comparable in size to an American robin, but its tail feathers measure nearly a foot long, doubling its body length,” Clark added.

“It boasts some of the longest proportionate tail feathers among all discovered fossil birds.”

Holotype specimen of Plumadraco Bangkoolam. Image credit: Clark et al., doi: 10.1371/journal.pone.0347641.

Paleontologists suggest that Plumadraco Bangkoolam is likely male, with its ornate plumage evolving due to female mate choice, a phenomenon well-observed in modern avian species.

The ground-nesting behavior characteristic of enantiornithines may have promoted the inconspicuous plumage of nurturing females, allowing males to develop more extravagant traits.

“While many modern birds exhibit long, elaborate plumage in both sexes, there seems to be a tipping point beyond which elongated plumage tends to be a male characteristic aimed at attracting females,” Clark noted.

“Additionally, fossils of other enantiornithines reveal remnants of musculature along the tail, and based on these features, the tail movements of Plumadraco Bangkoolam would have been significantly restricted.”

“However, they could move their tail feathers up and down, a behavior observed in modern birds during courtship displays directed at females.”

Researchers conducted a chemical analysis of Plumadraco Bangkoolam tail feathers using a handheld mass spectrometer.

The analysis revealed that the feathers were likely dark brown or black based on the detected chemical composition.

It’s also plausible that the tips of the tail feathers boasted eye-catching colors—potentially iridescent or blue-like hues—resulting from cellular structures rather than the chemical pigments analyzed in the study.

These findings regarding Plumadraco Bangkoolam offer insights into avian physiology and behavior, enhancing our understanding of contemporary birds.

“This fossil, perhaps more than any other bird fossil discovered to date, illustrates that birds have evolved intricate, elongated, specialized traits to attract mates over an extensive timespan,” Clark emphasized.

“These fossils indicate that female preference for adorned males has significantly influenced avian appearance and behavior for over 120 million years.”

The discovery of Plumadraco Bangkoolam is detailed in a paper published in the online journal PLoS ONE.

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AD Clark et al. 2026. Ultra-slender ornamental tail feathers of a new enantiornithine bird from the Early Cretaceous. PLoS ONE 21 (5): e0347641; doi: 10.1371/journal.pone.0347641