Hydrosaurus

Hydrosaurus is a genus of large agamid lizards native to Southeast Asia and nearby islands. Its species are known as sailfin lizards for the prominent crests and tall, laterally compressed tails used in swimming and display.

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Agamidae: Agamidae is a family of lizards that includes dragons, bearded dragons, and sailfin lizards. Hydrosaurus belongs to this lizard family, whose members often have conspicuous crests and displays.
Lateral undulation: Lateral undulation is locomotion produced by bending the body from side to side. Sailfin lizards propel themselves through water with side-to-side movements of the body and tail.
Hydrosaurus amboinensis: Hydrosaurus amboinensis is a large sailfin lizard species found on islands of eastern Indonesia. It is one of the best-known members of the genus and exemplifies its island distribution.
Water dragon: Water dragons are agamid lizards in the genus Intellagama or Physignathus, depending on the species. They are aquatic agamids sometimes confused with sailfin lizards, but belong to different genera.
Squamata: Squamata is the reptile order containing lizards, snakes, and worm lizards. The genus sits within Squamata through its placement in the lizard family Agamidae.
Prehensile tail: A prehensile tail can grasp or wrap around objects to aid climbing or handling. Despite its striking shape, the sailfin’s laterally flattened tail is adapted more for swimming than grasping.
Hydrosaurus pustulatus: Hydrosaurus pustulatus is a sailfin lizard species native to the Philippines. Its Philippine range illustrates the genus’s spread across distinct island groups.
Basilisk lizard: Basilisk lizards are Central and South American iguanian lizards known for running across water. Both are water-associated lizards, but basilisks and Hydrosaurus belong to different families and regions.
Dewlap: A dewlap is a fold of skin beneath an animal’s throat that can be extended for display. Like many agamids, sailfin lizards use throat skin and other visual signals in social displays.
Aquatic locomotion: Aquatic locomotion is movement through water by swimming, paddling, or other specialized propulsion. Swimming is a major function associated with the genus’s flattened tail and water-edge habitat.