The earless monitor lizard (Lanthanatus boreneensis) is a semi-aquatic, brown lizard native to northern Borneo. It is the only species in the family Lanthanotidae, a group related to the true monitor lizards, as well as to the beaded lizards.
Earless monitor lizards are around 20 centimetres in length, and have reduced eyes and limbs, a thick body, and strongly keeled scales. Despite the name, it is capable of hearing, although it lacks a tympanum or other visible signs of ears. It is a burrowing, nocturnal animal, feeding on earthworms and similar prey. Like its closest relatives, it is oviparous, although little else is known about its reproduction.
This species is very rare, and most known specimens are preserved, though these, also, are rare. The species is primarily of interest to scientists, since it is an evolutionary outgroup for both varanid and helodermatid lizards, as well as being one of the three lizards to possess venom (the other two being the two species of the related helodermatids.)