10 Gigantic Animal Ancestors

From dragonflies the size of large birds to sharks the size of large whales, here are the 10 most awesome giants from prehistory.



Just the head of this two-tonne monster was 1 metre long. (youtube.com)

With the Greek roots of its name meaning ‘chief of the turtles’, the Archelon glided across the temperate oceans of the Campanian Period possessing the dimensions of a large, round garden pool.

The Leatherback Sea Turtle of today can measure in at 2.1m (7 ft) long and 650kg (1433 lb) heavy. The Archelon absolutely dwarfed it. The largest specimen found, ‘Brigitta’, measures 4.6m (15 ft) from head to tail, 4m (13 ft) from flipper to flipper and weighed around 2.2 tonnes (4,900 lb), with the head alone 1 metre long. 

Achelons might’ve been found on soft, muddy sea floors moving slowly to use their beaks to crush an abundance of large molluscs and crustaceans, some measuring up to 1.2m (4 ft) in diameter. Alternatively, these sea monster’s huge flippers could have made them excellent long-distance swimmers with sharp beaks handy for shearing flesh from larger fish and reptiles, as well as soft-bodied creatures like the squid, jellyfish, or even other Archelon.

Archelon eventually died out mainly due to a cooling of the oceans. An increase of predation from emerging mammalian species on its hatchlings contributed to its eventual demise as well, perhaps 70 millions years ago.


This giant croc hunted large dinosaurs (hakaimagazine.com)

Today, crocodiles and alligators are the kings of the reptile world, but in the Campanian Period the Alligator’s largest ever ancestor could grow to more than half the length of a tennis court.

The largest ‘gators come out at 4.2 m (14 ft) long and weigh 473 kg (1,043 lb). Scientists guess the largest Deinos, by contrast, grew to a whopping 10-12m (35-39ft) long and 8.5 tonnes heavy based on a skull alone measuring 1.5m (4.8ft). So, it’s no surprise Deinos were the largest crocodilians of all time.

Deinosuchus, which translates from Greek as ‘terrible crocodile’, would’ve resembled the Alligator closely. With massive incisors towards the front of its maw and blunter teeth towards the back for crushing, Deinosuchus was the apex predator of its age, capable of an amazingly powerful bite force of anything from 18,000 newtons (N) up to 102,803 N (compared to a Tyrannosaurus Rex’s bite of just 35,000 N). As such it probably preyed on large ornithopods like the Kritosaurus around brackish water bays where other large predators avoided. And they’d ambush prey similarly to alligators, even utilising the dreaded ‘barrel roll’ method of killing. It might have also hunted giant sea turtles and large fish in coastal waters. Make no mistake, Deinosuchus was king. 

It eventually died during the Cretaceous–Paleogene extinction event.


The one-tonne snake (wired.com)

The giant of the snake world was the Titanoboa and it makes the modern Anaconda look like a grass snake by comparison.

Titanoboa lived in the first ever rainforests to exist in South America, specifically around coastal swampy areas on the proto Caribbean Sea. Its fossil remains were found in the northern coastal region of Colombia, existing during the Paleocene-Period.

Whereas our heaviest snake – the Green Anaconda – can be up to 5.21 m (17.1 ft) long and 70 kg (154 lb) heavy, the Titanoboa is estimated to have been around 12.8 m (42 ft) and weighed about 1.1 tonnes (2,500 lb). One full scale replica model measured a colossal 14.6m – over 1.5 London Buses long!

Although assumed to have been an apex predator, preying on crocodilians of the age, experts now believe its diet consisted more of aquatic creatures like 3m (10 ft) long lungfish, a dietary trait unique to Titanoboa among all boas. Because of its sheer weight, moving around on land would’ve been hard, and among the tree canopies out of the question, hence why it was mostly water bound.

Vorombe Titan

84 Prehistoric Madagascar ideas | prehistoric, prehistoric animals, extinct  animals
Vorombe Titan was the very largest of the massive Elephant Birds native to Madagascar.

The Vorombe Titan was the largest ever bird to exist and belonged to the ratite group of flightless birds with long, thin legs. It inhabited Madagascar just one millennium ago.

The largest bird to exist today – the Ostrich – grows up to 2.75 metres (about 9 feet) tall and weighs more than 150 kg (330 pounds). By comparison, the Vorombe may not have towered over the Ostrich at 3m, yet was much bulkier with a thicker neck, great hulking legs, and feet resembling more a T Rex’s than a big bird’s. And it was more than four times heavier at 650kg (1500 lbs). One specimen even reached 860 kg (1,900 lb) in weight. It was so enormous, its weight matched that of the smallest Sauropod dinosaurs. Its eggs were like large footballs.

Fortunately, with its giant talons and daggered beak, it was a herbivore and fed on fruit among the forests of Madagascar rather than early human settlers. As these people spread and multiplied across the large island, however, they preyed on these giant avians and destroyed their habitats from 600 AD until their eventual demise as late as 1200 AD. 


One of nature’s largest ever bugs discovered (dailystar.co.uk)

Greater levels of atmospheric oxygen in prehistory meant insects could also grow to ginormous dimensions. Meganeuropsis aka the Griffinfly is one of the largest insects ever discovered.

It resembled modern dragonflies/damselflies, with their two sets of wings and long thin bodies.

With the largest flying insects today, the Giant Dobsonfly boasting a 20cm (8 in) wingspan, the Griffinfly was more like the size of a large Sparrowhawk with one specimen measuring a 71cm (28 in) wingspan, and body length of 43 centimetres (17 in).

This huge bug flittered about in the Permian period 300-250 million years back at a time before dinosaurs truly ruled the world. It’s presumed to have been carnivorous like its modern descendent.


Giant jaguars, colossal bears done in by deadly combo of humans and heat |  Science | AAAS
Arctotherium won the arms race to dominate the food chain by simply outgrowing its competition (science.org)

The largest ever bear lived between 2.5 – 1 million years ago after its ancestors migrated down to South America after the formation of the Panamanian isthmus. Arctotherium, meaning ‘Bear Beast’ would’ve been able to sniff at the cranium of a tall man whilst on all fours before presumably devouring him.

The largest bear and land carnivore alive today, the Polar Bear, can be as big as 350–700 kg (770–1,540 lb), averaging 450kg (990lbs) and can stand on their hind legs to be almost 3 metres (10 foot). The Arctotherium would’ve stood even bigger, at 3.4–4.3 metres (11–14 ft) and weighed in at 1.6-1.7 tonnes (3,501 to 3,856 lb). 

Arctotherium’s size is explained by an evolutionary drive to outgrow its competition in order to secure the largest carcasses against hunters like the Smilodon Sabercat.


Paraceratherium was as tall as a Giraffe and heavy as a fully loaded bus. (thoughtco.com)

Now to the largest land mammal ever. The Paraceratherium brings to mind more the Star Wars AT-AT walkers than the largest land mammal today – the African Elephant.

This giant hornless rhino lived during the Oligocene epoch 34–23 million years ago. Incomplete fossils make its size hard to exact but estimates put its shoulder height between 4.8 – 7.4 metres (15.7 – 24.3 feet). Its weight was probably 15 to 20 tonnes (33,000 to 44,000 lb). The long neck supported a skull alone that was 1.3 metres (4.3 ft) long. This compares to a Giraffe’s height of 6 metres (20ft) and a male African Elephant’s weight of 6,8 tonnes (15,000 lbs).

They ranged across deserts and subtropical environments in small herds browsing on a variety of flora, safe in the knowledge there was barely a creature that could even gnaw on its legs – although evidence suggests the 10 metre long Astorgosuchus tried, and their young were obviously more vulnerable.

Gigantopithecus Blacki   

A truly giant ancestor of ours (newscientist.com)

The largest ever known primate existed 2 to 0.3 million years ago during the Pleistocene period, and whilst it stood erect you might feel more like you were staring up at King Kong less an Orangutan that is its closest relative.

Size estimates are pretty speculative based on teeth and jaw remains only, yet Gigantopithecus Blacki could grow up to 3.5 metres (11.5ft) standing and could be over half a tonne (1200lb) in weight. This compares to the largest primate alive today, male Eastern Lowland Gorillas which grow to 140–205.5 kg (309–453 lb) and 1.7 m (5.6 ft) upright.

This hulking giant was a herbivore that lived on a diet of fruit and leaves amongst the dense, humid tropical forests of modern-day southern China. The males’ larger size was due to a fierce competition for mates. The species’ size meant the large sabre toothed tigers of the time posed little threat to fully grown Blacki.

They died out 300,000 years ago because their forests retreated southward. This abandoned them to a dwindling diet and possible predation by Homo Erectus.

Pelagornis sandersi

Gliding vast distances across the oceans at speeds up to 37 mph (60 kmh), the Pelagornis Sandersi is the largest ever bird capable of flight and lived approximately 25 million years back in the Oligocene period. This bird is most closely related to today’s Great Wandering Albatross, however compared to the Albatross with its wingspan of up to 3.7 m (12ft), the Sandersi’s wingspan was so broad it exceeded the height of the tallest giraffes at 6.1 – 7.4 m (17 – 24 ft). It also weighed at least 48 pounds (21.8 kilograms), the same as a Roe Deer, so was too bulky to get airborne by any other method than launching itself off sea-cliff edges.

The Sandersi lived similarly to the Albatross in that it likely preyed on fish and squid close to the surface. Unlike the Albatross, however, it likely couldn’t touch down on water, thus spending more time airborne.


The notorious Megalodon, the ‘whale hunter’. (thenews.com)

The Otodus Megalodon is perhaps the most terrifying giant of all in this list; a swift sailing behemoth, with the proportions similar to a Sperm Whale yet with a gaping mouth filled with razor-edged teeth like that of its descendent, the Great White Shark. And the Ancient Greek translation of its name, ‘Big Tooth’ was apt; Meg’s teeth could protrude up to 18 cm (7 in).

Estimations of the largest Megalodon sharks are anything between 10 to an awesome 25 metres (32 to 82 ft) in length and 27.4 to 59.4 metric tons in weight. This compares to Great White sharks that grow up to just 6.1 m long. Even the largest fish alive today, the Whale Shark, comes in at 15 m (49 ft).

Estimates suggest they could exert a bite force of up to 108,500 to 182,200 newtons – that’s 18 tonnes per square inch! Together with their size and strength, Megalodon is likely the most supreme predator to ever exist, and in the 23 – 4 million years ago it prowled the seas none of the giant whale ancestors would’ve been too much to take down.


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