The analysis of nine 160‑million‑year‑old Anchiornis fossils reveals preserved feather pigmentation and molting patterns that indicate irregular, asynchronous feather replacement — a trait linked to flightless birds. Led by Dr. Yosef Kiat of Tel Aviv University and published in Communications Biology, the study uses molting as a new functional marker of flight ability in extinct species. The findings suggest some dinosaurs may have evolved basic flight traits and later lost them, complicating the traditional, linear view of flight evolution.
160‑Million‑Year‑Old Anchiornis Fossils Rewrite How Flight Evolved
160-million-year-old Anchiornis fossils. (photo credit: TEL AVIV UNIVERSITY)
A rare group of 160‑million‑year‑old Anchiornis fossils is prompting scientists to rethink long-held ideas about the origin and loss of flight. Researchers led by Dr. Yosef Kiat of Tel Aviv University analyzed preserved feather pigmentation and molting patterns in nine exceptionally intact specimens from eastern China and concluded that these animals likely underwent irregular feather replacement — a pattern associated with flightless birds.
New Evidence From Molting Patterns
Published in the journal Communications Biology, the study introduces a novel functional indicator for assessing flight capability in extinct species: feather molting patterns preserved in fossilized plumage. Unlike prior work that relied mainly on skeletal traits (wing proportions, bone structure, muscle attachments), this approach examines how feathers were grown, worn and replaced.
Because some Anchiornis fossils preserve original pigmentation — including white wing feathers with a distinctive black spot at the tip — the team could distinguish fully grown feathers from developing ones. Developing feathers showed pigment spots that had not yet aligned with the continuous black wing edge, revealing the sequence of feather replacement.
What Molt Patterns Reveal
“Feathers grow for two to three weeks. Once mature they detach from the blood vessels that fed them and become dead tissue. As they wear, they are shed and replaced in a cycle called molting,”
Dr. Kiat explained. In modern birds, those that rely on flight generally molt in a symmetrical, orderly sequence that preserves wing function. Non‑flying birds exhibit more irregular, asynchronous molting. Across the nine Anchiornis specimens, the researchers found irregular feather replacement rather than the coordinated pattern expected for flyers.
Implications For The Evolution Of Flight
These results suggest that some members of the Pennaraptora clade — the group that includes the ancestors of modern birds — may have possessed primitive aerial abilities at some point and later lost them in certain lineages. That challenges a simple, linear model in which flight evolved once and only progressed toward greater aerial skill.
“Feather molting may seem like a technical detail, but when observable in fossils it can overturn long‑standing ideas about the origin of flight,” Kiat said. The study adds to growing evidence that wing evolution was complex and dynamic: feathers served multiple roles (thermoregulation, display, insulation) and the selective pressures shaping flight capability varied across time and environments.
Why This Matters
By combining exceptional soft‑tissue preservation with a biologically informed framework, the research provides direct behavioral insight into how some feathered dinosaurs lived. Anchiornis now joins other feathered but likely flightless dinosaurs, underscoring that wings do not always imply sustained powered flight.
Study: Led by Dr. Yosef Kiat (Tel Aviv University) with collaborators in China and the United States; published in Communications Biology. Fossils: nine Anchiornis specimens from eastern China, ~160 million years old.
