HOME | DD

Description

A selection of extinct species from the lizard family Varanidae, to scale.

Varanids or monitors are an incredibly successful group of lizards. The earliest species (Ovoo, Aiolosaurus and Telmasaurus) are known from Late Cretaceous Mongolia and range through to the modern day distribution across Africa, Eurasia and Australasia. Early species such as the long-tailed Saniwa even successfully spread to North America in the Eocene. In general they have a conservative body plan, with all species roughly similar despite the differences in size. The tiny 23 centimetre Dampier Peninsula monitor is the smallest species ranging up to the gigantic Pleistocene megalania Varanus priscus, the largest known lizard to walk on land**. Based on all modern species being active pursuit hunters (apart from a few frugivorous species) with a high aerobic capacity, we can assume that this was possibly true for extinct relatives too. Some species also show high levels of cognition, being able to recognise faces, count, problem-solve and are also capable of training.

* All varanids from the Miocene to modern species fall within Varanus, but these are further split them into various subgroups.

* Megalania was originally given it's own genus, but was subsumed under Varanus as it's closest relatives are the extant Komodo dragon and Lace monitor. Size estimation by researchers has plagued megalania. Anything between 3.5 and nearly 8 metres long has been suggested, however when using Komodo dragons as a model, large individuals come in around 7 metres long. Although they undoubtedly overlapped in time with early modern Australian aboriginals, which must have been a frightening experience, we don't have any evidence of interaction.

* Komodo dragons of Indonesia are the largest species of varanid alive today at 70 kilograms and 2.6 metres long. Fossils have been also found in Pleistocene Northern Australia, strengthening the link with megalania.

* Some species such as Aiolosaurus are more closely related to a secretive semiaquatic species living on Borneo known as the Earless monitor. Whether Lanthanotus and it's closest fossil relatives are in a discrete subfamily (Lanthanotinae) or a separate family (Lanthanotidae) seems to depend on preference, but they are definitely the closest relatives of varanids.

* For a species that lives in rivers, Lanthanotus surprisingly has a prehensile tail! It is presumably used to hold on to stones in strong currents.

* Telmasaurus is probably even more distantly related, sister group to both varanids and lanthanotids. It was the largest of the very early varanoids.

** Another group of lizards, the aquatic mosasaurs of the Late Cretaceous reached even greater lengths up to 13 metres long.

[Note: edit made to text, as per comments].

Description

A selection of extinct species from the lizard family Varanidae, to scale.

Varanids or monitors are an incredibly successful group of lizards. The earliest species (Ovoo, Aiolosaurus and Telmasaurus) are known from Late Cretaceous Mongolia and range through to the modern day distribution across Africa, Eurasia and Australasia. Early species such as the long-tailed Saniwa even successfully spread to North America in the Eocene. In general they have a conservative body plan, with all species roughly similar despite the differences in size. The tiny 23 centimetre Dampier Peninsula monitor is the smallest species ranging up to the gigantic Pleistocene megalania Varanus priscus, the largest known lizard to walk on land**. Based on all modern species being active pursuit hunters (apart from a few frugivorous species) with a high aerobic capacity, we can assume that this was possibly true for extinct relatives too. Some species also show high levels of cognition, being able to recognise faces, count, problem-solve and are also capable of training.

* All varanids from the Miocene to modern species fall within Varanus, but these are further split them into various subgroups.

* Megalania was originally given it's own genus, but was subsumed under Varanus as it's closest relatives are the extant Komodo dragon and Lace monitor. Size estimation by researchers has plagued megalania. Anything between 3.5 and nearly 8 metres long has been suggested, however when using Komodo dragons as a model, large individuals come in around 7 metres long. Although they undoubtedly overlapped in time with early modern Australian aboriginals, which must have been a frightening experience, we don't have any evidence of interaction.

* Komodo dragons of Indonesia are the largest species of varanid alive today at 70 kilograms and 2.6 metres long. Fossils have been also found in Pleistocene Northern Australia, strengthening the link with megalania.

* Some species such as Aiolosaurus are more closely related to a secretive semiaquatic species living on Borneo known as the Earless monitor. Whether Lanthanotus and it's closest fossil relatives are in a discrete subfamily (Lanthanotinae) or a separate family (Lanthanotidae) seems to depend on preference, but they are definitely the closest relatives of varanids.

* For a species that lives in rivers, Lanthanotus surprisingly has a prehensile tail! It is presumably used to hold on to stones in strong currents.

* Telmasaurus is probably even more distantly related, sister group to both varanids and lanthanotids. It was the largest of the very early varanoids.

** Another group of lizards, the aquatic mosasaurs of the Late Cretaceous reached even greater lengths up to 13 metres long.

[Note: edit made to text, as per comments].