A research team from the National Taiwan Normal University has clarified the status of a secretive reptile through a new study published in the open-access journal ZooKeys. Led by Si-Min Lin, the team focused on the Formosan legless lizard, scientifically known as Dopasia formosensis. These lizards are among the most secretive and least studied groups in Taiwan, living primarily under leaf litter and humus in moist forests. This elusive behavior makes field observations and ecological studies extremely difficult.
The study resolves a century of taxonomic debate over whether Taiwan’s legless lizards comprise one species or two. For decades, these populations were classified as Dopasia harti, a status complicated by the loss of the original Dopasia formosensis type specimen after World War II. To stabilise the identity of the species and re-establish it as the distinct lineage Dopasia formosensis, the research team has designated a “neotype” – this is a new physical specimen that serves as the official reference for the species name.
Physical Characteristics
The Formosan legless lizard is a medium-sized reptile that lacks external limbs. Adult males typically have a body length between 175 and 230 millimeters, while females are similar in size. A key feature of this species is its exceptionally long tail, which can be nearly double the length of its body.
People often mistake these lizards for snakes, but they possess several distinct features that set them apart. Unlike snakes, legless lizards have external ear openings, although they are quite small. They also have moveable eyelids, which means they can blink, a trait no snake possesses. Further, these lizards have a prominent lateral fold, which is a longitudinal groove running along each side of the body. This fold allows the skin to expand, which is useful for breathing and when females are carrying eggs.
Etymology and Colouration
The species name formosensis is rooted in the historical name for Taiwan, “Formosa”, derived from the Portuguese phrase Ilha Formosa (“Beautiful Island”). The name combines this geographical reference with the Latin suffix “-ensis”, which indicates the place of origin.
Bottom: Landscape of the collection site of the neotype near Mingchi, Yilan, Taiwan. (Photo credits: Chung-Wei You and Kai-Xiang Chang).
The study also clarified a major point of ambiguity regarding the species’ color. Previously, lizards with bright blue spots were thought to be a different species than those without them. The research team confirmed that these markings are actually a form of sexual dichromatism – while females and young lizards usually have a plain pale brown or bronze color, fully mature adult males often display these conspicuous blue markings as a form of secondary sexual signalling.
Behavioural Characteristics
Since these legless lizards are so rarely seen, the research team relied on citizen science data from the Taiwan Roadkill Observation Network to gather information. In the wild, these lizards prefer high-humidity environments in mid-elevation forests with dense canopy cover.
The researchers also noted parental care as a key behavioural characteristic for the species, suggesting that they may exhibit more complex social behaviors than many other reptiles. In related species within the Dopasia genus, for instance, females are known to exhibit egg-guarding behavior, where they remain with their clutch to protect it from predators and environmental hazards until the offspring hatch.
A prior study documenting the species now recognised as Dopasia formosensis (previously identified as D. harti) notably also detailed its interesting fighting behavior. The encounter begins with a ritualised display where the lizards circle each other with mouths agape, flattened throats, and elevated forebodies. This posturing eventually escalates into physical combat, characterised by one-sided biting and rotational rolling as the males attempt to subdue one another.
Conclusion
The Formosan legless lizard is currently listed as a protected species under Taiwanese law. The research team emphasises that a stable scientific name and clear understanding of the species is critical for future conservation.
“Through these efforts, we aim to provide a more stable framework for future taxonomic, ecological and conservation studies of this overlooked lizard group.”
The Research Team
By making their data openly available, they hope to encourage further study of these unique animals across East Asia.
Original source:
Lin S-M, Shen C-C, Lin T-E, Liang Y-J, Chang W-H (2026) Redescription and neotype designation of Dopasia formosensis (Kishida, 1930) (Squamata, Anguidae) from Taiwan. ZooKeys 1270: 69-98. https://doi.org/10.3897/zookeys.1270.173752
For more articles on zoology, visit the ZooKeys website and follow the journal on BlueSky and Facebook.
