I think when it comes to reptiles, easily the most interesting are the monitor lizards and their relatives. The monitor lizards are scientifically known as the members of the genus Varanus within the family Varanidae (which, in turn, is a family within the superfamily Varanoidea), and are widely considered to be the lizards with the most intelligence. The largest extant (still living, opposite of extinct) lizard today, the Komodo dragon, is a member of this family, as is Megalania (often referred to as Varanus prisca), the largest known lizard ever to have existed. Let's learn a bit more about these interesting reptiles!
American biologist Eric Pianka (link included in References section), the monitor lizards as a group are thought to have evolved on the continent of Laurasia (see map below) earlier than 65 million years ago (MYA), before even the dinosaurs died out. After evolving in Laurasia, they then dispersed into the continents of Africa and Australia. As of the writing of his paper, 44 species of monitor lizard are around today, with around 27 of these native to Australia, where the highest species density of monitor lizards are. In the tropics of northern Australia, up to ten species of Varanus can reside together!
There are numerous families related to the monitor lizards within the superfamily Varanoidea, both living and dead, such as the earless monitor lizard, the sole member of the family Lanthanotidae. The other extant family within the superfamily Varanoidea is the family Helodermatidae, which includes the beaded lizards and the Gila monster from southwestern North America, Mexico, and Guatemala. However, in my opinion, it is the extinct family Mosasauridae that is the most interesting of the monitor lizard relatives.
The mosasaurs were the dominant marine predators throughout the Late Cretaceous Period, and were wiped out by the traumatic K/T Extinction Event, just like the dinosaurs. Some of these mosasaurs could grow to enormous lengths, such as Tylosaurus, the apex predator of the Western Interior Seaway of North America during the Cretaceous Period. Tylosaurus could grow to an enormous 50 or so feet long, and fossil discoveries of the stomach of this creature indicate that it fed on pretty much everything that swam in the sea: the remains of sharks, the flightless diving bird Hesperornis, fish, plesiosaurs, and even smaller mosasaurs have been found in the stomachs of Tylosaurus fossils!
The mosasaurs share something else in common with the monitor lizards: they both have a third eye on top of their head. It's not the same as the eyes we have on our head, or even the eyes that the mosasaurs and monitor lizards have on their heads, either. A good comparison is if you close your eyes and look at a light source, and then move your hand back and forth in front of your face. You can see something moving , right? Just a shadow, but you can still tell that something is there. That's kind of what the third eye of the monitor lizards and the mosasaurs is like. If you are a baby Tylosaurus swimming in the sea and you see something pass overhead, you are going to swim to safety as fast as you possibly can: there are a lot of things in this sea that would barely noticed they swallowed you. However, if you are a 50-foot long adult Tylosaurus and you see a shadow swim above your head, you are almost certainly going to go investigate. Whatever it is, it's probably edible!
Another interesting thing that the mosasaurs most likely shared with the monitor lizards is their forked tongue, similar to that of snakes. But what purpose does this forked tongue served? Well, when the animal sticks the tongue out of its mouth, it is smelling the air. As it draws the tongue back in, scent particles are pulled in as well. The fork-tongued creature is able to determine which side of the forked-tongue has more scent particles on it. If the animal was attempting to locate a dead animal or something like that, and its head was facing directly towards where the dead animal scent particles were floating from, the reptile would know that it was on the right track. If, however, the fork-tonguer was facing due north, and the dead animal was due west of its position, when the tongue is drawn into the mouth, its owner can tell that there are more dead animal scent particles on the left side of the tongue, as opposed to the right, and now knows which way it must go to find its meal. Pretty neat!
Can't get enough of the monitor lizards? Well, below I have links to five videos featuring some monitor lizards (one spiny-tailed monitor, four Komodo dragon)! Enjoy!
Spiny-Tailed Monitor Attempted Feeding
Komodo Dragon Moving Around at the Cheyenne Mountain Zoo
Komodo Dragon Relaxin' to the Maxin'
Up Close and Personal With The Komodo Dragon at the Cheyenney Mountain Zoo
Komodo Dragon Close Up at the Denver Zoo
And now, for some pictures of various monitor lizards I have taken over the years! First off is Herkemer, the resident Dumeril's Monitor Lizard at the Morrison Natural History Museum!
Cheyenne Mountain Zoo!
baby Komodo dragons at the Phoenix Zoo in Arizona! They are pretty darn cute!
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