By Kshitij Kulkarni
In prehistoric times, the Earth was home to a wide variety of creatures that we would consider to be the stuff of nightmares. From elephants and rhinos that could easily look into the first floor of a house and monitor lizards the size of SUVs to cow-sized rodents, the Cenozoic Era, the era following the extinction of the dinosaurs did have its own share of giant creatures. Animals growing to such large sizes has been attributed to many causes; the most fundamental ones being a sudden surge in atmospheric oxygen levels 2.45 million years ago that levelled at 1.85 million years ago, abundance of prey, environmental conditions etc.
In comparison, they significantly dwarf many of their modern relatives to such an extent that it is hard to believe that they are related. Considering most of them lived side-by-side with early humans, it does not seem so far-fetched to assume that these large beasts were the inspiration for quite a few mythical creatures that survived through our ancestors’ collective subconscious. Let’s take a look at some of them .
- Varanus priscus or Megalania
The extinct monitor lizard Varanus priscus (aka Megalania, or Giant Ripper Lizard) belongs to the genus Varanus, which is where all modern-day monitor lizards are classified. During the Pleistocene epoch, about 50,000 years ago, they went extinct as a part of the Australian megafauna. The eminent palaeontologist Sir Richard Owen first described them in 1859, based on three vertebrae collected from a tributary of the Condamine River, west of Moreton Bay in eastern Australia. The rest of the animal is only known through partial, incomplete remains.
The animal is 3.5-8 m in length and weighs 91-1940kg. This huge disparity in size is due to the aforementioned incomplete remains; the length and weight are estimated by assuming their similarity to modern monitors. The whole thing is therefore based on speculation. This being said, the largest lizard alive today is the Komodo dragon, which is 3m long and weighs up to 100kg.
Megalania was an apex predator, preying upon huge wombats such as Diprotodon and Phascolonus, as well as large kangaroos such as Procoptodon, who filled the niche of giant herbivores. Given their musculature and long tail, they knocked off animals with a tail swipe and finished them off with their jaws and claws. Their saliva might have been venomous, much like current ones, but there is no way of knowing for sure. They were covered with scales that looked like chainmail. Climate change, the migration of early people to Australia, the loss of megafauna, and competition from new carnivores all contributed to their extinction.
- Palaeoloxodon namadicus, the giant Proboscidean
Image source: Wikimedia Commons
Palaeoloxodon namadicus, also known as the Asian straight-tusked elephant, was a Pleistocene Asia megafauna species that existed in regions between India and Japan. They are one of the descendants of straight tusked elephants.
The structure of their skulls varies from those of a contemporary elephant. Comparing femur length and relative growth rates helps researchers to determine the size of the incomplete skeletons and is often used in studies to estimate their size.
P. namadicus stood up to 5.2m (17ft) tall at the shoulders, tall enough just to stare down an adult person on the first level of a building. They weighed between 20,000 and 22,000 kg, about four times the weight of a male African wild elephant (6,000kg). (For comparison, a Volvo bus weighs 22,200 kg dry i.e. without fuel and oil.) As a result, it is a strong contender for the title of ‘biggest land animal’ ever.
They went extinct between 50 to 30 thousand years ago, around 30 thousand years after Homo sapiens arrived on the scene. This occurred at the same time as a small megafaunal extinction event, in which 100 genera went extinct on every continent except Antarctica. Climate change, as well as hunting by early humans, are thought to have contributed to their extinction. Despite the fact that they shared their environment with some machairodonts (sabre-toothed cats), a healthy adult would have been unaffected by them.
On a separate note, imagine a world where humans managed to tame these beasts. Who wouldn’t want army units the size of buses rushing at their adversaries? Given the fact that ancient Indian rulers maintained an elephant division, it is safe to say that they would be the overlords of the entire world, had they managed to include these behemoths in their stables.
- Terror birds of the extinct family Phorusrhacidae
The Red-legged Seriema (Cariama cristata) is 2 feet high raptorial bird found in South America which feeds on snakes, lizards, and rodents. It prefers to live in open woodlands. Many bird watchers admire this bird for its brave attitude against snakes, as well as its keen talons and powerful beak. What if I told you they used to be associated with a bigger, more intimidating relative?
The Phorusrhacidae family includes gigantic, tall flightless birds that originated in America and one species (Titanis) that subsequently moved to North America during the Great American Exchange, which occurred 3.5 million years ago as a result of the creation of the Isthmus of Panama. Phorhusrachos, a 2.5m tall terrorbird that was the first of its type to be found, gave the group its name. Florentino Ameghino namedit in 1887 after discovering numerous mostly intact skeletons. The oldest terror bird, Paleopsilopterus, was discovered in Brazil and datesback to sixty million years ago.
Their long legs indicate that the terror birds, especially the larger ones, could carry themselves high above the ground at top speeds reaching 45 km/h.
The head was carried high above the ground on a long neck. Brain CAT scans indicate
- Well developed inner ears for balance purpose
- Could hear a large range of frequencies
- Poorly developed olfactory part of the brain
- Well developed frontal cortex, i.e., as an indicator of cognitive predation
- Excellent vision.
All the above factors indicate an active predator rather than a scavenger. The beak was hollow and could withstand a great deal of downward pressure but not lateral pressure. It was sharpened with a pronounced tip. The hunting strategy was ambush, said to be similar to that of contemporary Seriema birds, which caught smaller animals with their beaks and threw them against a hard surface, killing them and fracturing their bones (to swallow whole). For larger animals, the beak was used as a pickaxe, aiming at the vulnerable spots. Simulations show it was capable of shattering the spine and caving in the skull.
The fossil record of the terror birds seems to end at approximately 2 million years ago. Their extinction was caused by two factors.
- Many powerful predators like Smilodon, wolves, and others moved to South America as a result of the Great American Interchange. They were able to soon outcompete the terror birds. Large predators like Arctodus filled the scavenger role that provided a food source for these terror birds.
- The forested scrubland,which the terror birds were accustomed to, gradually gave way to desert steppes and savannas, exposing them to their prey from afar.
This occurred because the Andes cast a rain shadow over the rest of South America.
These were only a few of the colossal prehistoric beasts that once roamed the earth. Let us be grateful that they are no longer among us.
References :
- Encyclopedia Britannica. seriema | bird. [online] Available at: https://www.britannica.com/animal/seriema
- http://www.prehistoric-wildlife.com, D. Phorusrhacos. http://www.prehistoric-wildlife.com/species/p/phorusrhacos.html
- http://www.prehistoric-wildlife.com, D. Terror Birds of the Phorusrhacidae. http://www.prehistoric-wildlife.com/articles/terror-birds-of-the-phorusrhacidae.html
- Beasts that once roamed the Indian subcontinent could hold clues to evolution and extinction. https://india.mongabay.com/2021/02/beasts-that-once-roamed-the-indian-subcontinent-could-hold-clues-to-evolution-and-extinction/
- Palaeoloxodon namadicus. https://prehistoric-fauna.com/Palaeoloxodon-namadicus
- The Largest Beasts to Walk the Earth. https://www.nationalgeographic.com/science/article/the-largest-beasts-to-walk-the-earth
- http://www.prehistoric-wildlife.com, D. Varanus priscus (Megalania). http://www.prehistoric-wildlife.com/species/v/varanus-priscus.html
The XZA Chronicle 
Oooh this was a very very very nice read and super informative. Thanks for sharing!!!
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