Hydrosaurus – Sailfin dragons

Native to the Philippines, Indonesia, and New Guinea, these large, semi-aquatic lizards are famous for the dramatic sail-like structure on their tails, which resembles the fin of a fish or the spine of a miniature dinosaur. This “sail” is made of extended spines covered with skin, giving the lizard a bold, dragon-like appearance and inspiring their popular nickname.

Sailfin dragons have muscular bodies, long tails, and strong limbs tipped with sharp claws for climbing. Their colors can range from olive green to dark brown, often with hints of blue, purple, or black, depending on the species and age. Males are generally larger and flashier than females and have more developed sails and head crests. Their tails aren’t just for show — they help with swimming and balance, especially when moving through rivers and streams in tropical forests.

Hydrosaurus lizards are diurnal (active during the day) and omnivorous, feeding on a mix of plants, fruits, insects, and small animals. They often live near freshwater sources and are excellent swimmers — when threatened, they can dive into water and stay submerged for several minutes to escape predators. Despite their size and fierce appearance, sailfin dragons are usually shy and quick to flee from danger. They’re also skilled climbers, often seen basking on tree branches or rocks near riverbanks.

Sailfin dragons can run short distances on their hind legs, giving them a comical, almost dinosaur-like sprint. Some juveniles even run across water for a few steps — a trait they share with their smaller cousins, the basilisk lizards, earning them comparisons to “Jesus lizards.” Another cool detail is that their impressive sail may be used not only for swimming but also for thermoregulation (absorbing or releasing heat) and attracting mates during the breeding season.