12 Extinct Animals That Once Roamed the Earth

The earliest settlers in the New World were astounded by the passenger pigeon, a bird with such massive flocks that it could take days for them to pass overhead, darkening the sky in their wake. Any farmer unlucky enough to host these birds found his crops completely devoured in mere moments.

Then, quite rapidly, the most abundant bird in North America vanished from the Earth.

The extinction of the passenger pigeon illustrates a profound conflict between nature and humans. With a staggering population of 3 to 5 billion upon the arrival of the first Europeans, these birds could not coexist with expanding human activities. The creatures were decimated by relentless hunting and deforestation, and as the 20th century began, their numbers plunged.

Contributing to their demise was climate change, which altered habitats and food sources crucial for their survival. The extinction was only becoming apparent at the start of the 20th century; by 1914, the last known bird, Martha, died at the Cincinnati Zoological Garden.

The Tasmanian tiger, or thylacine, was a distinctive marsupial carnivore native to Tasmania, Australia and New Guinea. Recognized by its striped back and dog-like appearance, thylacine was the largest carnivorous marsupial of modern times.

Despite its adaptability, the species could not withstand the pressures of humans hunting them. With support from government bounties, farmers who blamed the creatures for livestock losses actively pursued their elimination.

This direct hunting, along with habitat destruction and competition from introduced species like dogs, led to their sharp decline and, eventually, the species' extinction. The last known thylacine died in captivity in 1936.

Steller's sea cow, a massive marine mammal, was discovered in 1741 by the naturalist Georg Wilhelm Steller during the Vitus Bering expedition to the Commander Islands in the Bering Sea. Incredibly, within just 27 years of its discovery, the Steller's sea cow was declared extinct.

Early explorers and fur traders sought its meat, fat and hide, leading to the sea cows' rapid disappearance. Although its natural habitat — kelp-rich cold waters — was not directly altered by human activity, the overexploitation effectively degraded its ecosystem.

This human-induced event is often cited in discussions regarding the Anthropocene or the sixth mass extinction, emphasizing the accelerated rate at which biodiversity is currently being lost and resulting in more and more endangered animals.

The quagga is a mammal closely related to modern horses and zebras. In fact, it looks like a cross between a horse and a zebra (but different from a zorse), with stripes only on its head and neck that disappear as they approach the brownish hindquarters of the animal.

The quagga was native to desert areas of South Africa until it was hunted to extinction in the 1870s. The last captive animals died in Europe in 1883, but the species is making a comeback — sort of.

The Quagga Project, initiated in the 1987, aims to selectively breed zebras to bring back the quagga's distinctive physical traits. While the project has successfully bred animals that visually resemble the historic quagga, they are not genetically identical to the original quagga population.

This re-bred line is sometimes referred to as "Rau quaggas," named after Reinhold Rau, one of the project's founders.

Archaeopteryx, a creature that combines bird and dinosaur traits, has intrigued paleontologists since its discovery in the mid-1800s. Exhibiting dinosaur-like characteristics — such as a full set of teeth, a flat breastbone, a long bony tail and wing claws, along with bird-like feathers and wings — Archaeopteryx was not primarily adapted for flight.

Instead, the small birdlike creature likely engaged in running, leaping, climbing and gliding within its natural habitats during the Jurassic Period, about 150 million years ago. These environments were complex and existed long before the appearance of early humans.

This species eventually went extinct, possibly due to significant ecological changes. As the most primitive known bird, Archaeopteryx serves as a crucial evolutionary link between modern birds and dinosaurs, marking a pivotal point in the evolutionary history of birds.

Of all the formidable creatures found in the fossil record, the saber-toothed cat — also inaccurately called the saber-toothed tiger — is one of the most striking.

With its long, dagger-like canine teeth and powerful physique, this predator was a dominant force during the Cenozoic Era. It inhabited regions across North America and Europe and went extinct approximately 10,000 years ago.

A significant number of saber-toothed cat specimens have been unearthed at the famous La Brea Tar Pits in Los Angeles, California, leading to its designation as the state fossil of California.

Despite their fearsome appearance and formidable hunting skills, it appears that saber-toothed cats also demonstrated social and nurturing behaviors. Many fossils show evidence of healing and recovery from injuries and diseases, indicating that these formidable predators may have supported each other through tough times.

The plesiosaur, a large aquatic reptile, thrived in the world's oceans from the Jurassic to the Cretaceous periods, spanning approximately 201 million to 66 million years ago. This diverse group included species with extraordinarily long necks and small heads, some reaching lengths of up to 65 feet (about 20 meters).

Plesiosaurs often feature in discussions about the Loch Ness monster, a legendary creature reputed to inhabit Scotland's Loch Ness. While some speculate that sightings could be a surviving plesiosaur, this notion is scientifically unsupported and highly romanticized.

Unlike dinosaurs, plesiosaurs were adapted for life in water with bodies suited for powerful swimming, featuring four large, paddle-like limbs that allowed them to maneuver adeptly through aquatic environments.

Hallucigenia, a notable creature from the Cambrian Period over 500 million years ago, exemplifies the remarkable burst of evolutionary innovation of that era. This period witnessed the emergence of many major animal groups and featured a diverse array of unique and experimental body plans.

Named for its bizarre appearance, which seems like something from a psychedelic vision, Hallucigenia had an elongated body with a row of slender spines on one side and a series of tentacle-like appendages on the other.

Initially, scientists were baffled by its structure, leading to misconceptions about its orientation. Early interpretations mistakenly placed it walking on its spines, with the appendages thought to be mouthparts.

Subsequent research has clarified that these tentacle-like structures are actually paired appendages used for walking, while the spines likely served as a defense mechanism against predators.

Contrary to popular belief, the dodo was not an unintelligent or lazy bird. It evolved in a predator-free environment on Mauritius, an island in the Indian Ocean, where it enjoyed abundant food resources on the ground. In such conditions, the dodo had no evolutionary pressure to maintain the ability to fly and moved at a leisurely pace on foot instead.

This serene existence ended abruptly in the late 16th century with the arrival of European explorers. The dodo quickly became an easy target for hunters, primarily because it provided a readily available source of meat for weary sailors.

Additionally, the introduction of invasive species such as pigs, dogs and rats by these explorers devastated the dodo populations. These animals destroyed the dodo's ground nests and consumed their eggs, which were unprotected and accessible.

Within a few decades of human contact, the dodo was hunted to extinction.

If there is one animal emblematic of the Ice Age, it is undoubtedly the woolly mammoth. This giant, shaggy beast — renowned for its long, curved ivory tusks and massive trunk — roamed across the northern parts of the globe.

Contrary to the claim that the earliest mammoths were small, amphibious creatures from North Africa, mammoths actually originated from the same lineage as modern elephants, adapting over time to the cold environments of the northern latitudes.

The woolly mammoth (one of several species of mammoths) was one of the more robust species, well-adapted to the frigid climates. It migrated from Eurasia to North America across the Bering Land Bridge during the late Pleistocene epoch.

Unfortunately, the woolly mammoth could not withstand the combination of climate changes and human-hunting pressures. The last known population of woolly mammoths lived on Wrangel Island in the Arctic Ocean until about 4,000 years ago, significantly later than the often cited date of 10,000 years ago.

When researchers unearthed remains in a cave on the Indonesian island of Flores in 2003, the discovery was groundbreaking.

The remains, which belonged to several individuals with notably small heads and a height of about 3 feet (approximately 0.91 meters), sparked a lively debate: Were these a new species of hominid, a type of advanced ape or humans with a condition that caused their small stature?

These individuals were eventually classified as a distinct species of hominid and were nicknamed "Hobbits." Officially named Homo floresiensis, or "Flores man," this species is believed to have lived from as recently as 50,000 to 60,000 years ago, with some evidence suggesting survival until about 12,000 years ago.

This timeline suggests that Homo floresiensis coexisted with modern humans (Homo sapiens) for a significant period, raising intriguing questions about potential interactions. Flores man's use of caves and tools similar to those of early humans underscores its unique place in human evolutionary history.

Topping our list, the Tyrannosaurus rex is renowned worldwide as one of the most formidable predators to have ever roamed the Earth.

This colossal dinosaur, measuring up to 40 feet (about 12 meters) in length, possessed a massive head and powerful jaws capable of delivering a devastating bite. The mere sight of its fossil remains can send shivers down the spine of anyone imagining an encounter during the Cretaceous Period.

Despite their dominance, the question of why Tyrannosaurus rex and other dinosaurs went extinct remains one of paleontology’s most enduring mysteries. T. rex didn't face the same threats as critically endangered species of today, such as hunting and human-induced habitat degradation.

The prevailing theory suggests a catastrophic event, likely a massive meteor impact or significant volcanic eruptions, led to their demise approximately 66 million years ago. This extinction event caused widespread havoc and dramatically reshaped life on Earth.

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.