Paleontology's Scandal — The Oculudentavis Affair

Incorrect reconstruction of Oculudentavis khaungraae（感謝Han Zhixin提供）

Anyone who follows paleontological research has likely heard of the Oculudentavis incident, one of the most notable controversies in the field during 2020. In March of that year, the prestigious journal Nature published a study led by paleontologist Lida Xing of the China University of Geosciences. The paper described a remarkable fossil preserved in amber from Kachin State in northern Myanmar, dated to approximately 98 million years ago during the Cenomanian stage of the Late Cretaceous.

Encased within the amber was an extraordinarily small skull fossil measuring only about 1.5 centimeters in length. The specimen possessed a long, tapered snout bearing teeth, as well as very large eye sockets surrounded internally by a complex ring of scleral ossicles. Compared with fossils preserved in sedimentary rock, amber has a much greater capacity to preserve delicate remains of extremely small organisms, making such discoveries possible.

Based on their observations of the skull, the researchers concluded that the specimen represented a bird from the Mesozoic era. Because the skull was roughly comparable in size to that of a modern hummingbird, the study claimed it represented the smallest known dinosaur fossil ever discovered. The species was named Oculudentavis khaungraae. The amber specimen had been found on a small island in the region, and the authors proposed that such extreme miniaturization might have resulted from insular dwarfism.

They further suggested that the fossil displayed several anatomical features deviating from typical avian skeletal patterns, including spoon-shaped scleral ossicles, teeth along the margins of the jaws, and pleurodont-like tooth implantation. These unusual traits were attributed to evolutionary modifications associated with island dwarfism. In their phylogenetic interpretation, the researchers placed Oculudentavis among early birds, outside Ornithuromorpha, more derived than Archaeopteryx yet more primitive than Jeholornis. They also acknowledged the possibility that it might belong to Enantiornithes.

However, skepticism emerged almost immediately. Just one day after the paper was published, criticism began circulating among paleontologists. Within roughly a week, several other Chinese researchers uploaded a critique to the BioRxiv preprint server challenging the interpretation. They argued that the skull exhibited too many characteristics inconsistent with dinosaurs.

One particularly puzzling feature was the absence of an antorbital fenestra, an opening in the skull that remains a defining trait of archosaurs and is still retained in modern birds. In addition, in most birds the maxilla ends beneath the anterior margin of the orbit, whereas in Oculudentavis the maxilla extended beneath more than half of the orbit. Combined with the unusual scleral ring and dental morphology previously mentioned, these features strongly indicated affinities with squamate reptiles—specifically lizards—rather than archosaurs. The authors of the BioRxiv critique even remarked pointedly that the eyes and teeth of Oculudentavis clearly demonstrated that the fossil was not a bird at all. By July of the same year, the original paper identifying it as a bird had been formally retracted.

Correct reconstruction of Oculudentavis khaungraae（感謝Clumsystiggy提供）

Given Lida Xing's status as a professional paleontologist, it was difficult for many observers to imagine how such an obvious misidentification could occur. If the fossil had simply been misinterpreted initially, it raised serious questions about both the author's judgment and the peer-review process. As the controversy unfolded, another amber specimen was discovered that included not only a skull but also a portion of the body, providing even stronger evidence that the animal was in fact a lizard. Some critics speculated that Xing might already have known of the second specimen but chose to overlook it in order to attract attention within the paleontological community. The discrepancies in the original interpretation were simply too numerous, and the episode ultimately left him facing accusations of academic misconduct.

More complete amber fossil of Oculudentavis khaungraae（感謝Mónica M. Solórzano‑Kraemer, Enrique Peñalver, Mélanie C. M. Herbert, Xavier Delclòs, Brian V. Brown, Nyi Nyi Aung & Adolf M. Peretti提供）

The genus name itself—Oculudentavis—derives from the Latin oculu- (“eye”), dent- (“tooth”), and -avis (“bird”). Even though the animal has since been recognized as a long-snouted lizard rather than a bird, the discoverer has not proposed a new name. As a result, this lizard continues to carry a name that forever labels it a “bird”.

Author: Shui-Ye You

Reference:

Xing, L. et al. (2020). Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature.