Arctodus simus

One of the largest bears of all time, Arctodus simus first appears in the fossil record approximately 1.6 million years ago, in the Pleistocene Epoch.

There are two members of the genus Arctodus (Greek for “bear tooth”): A. pristinus and A. simus. It is believed that A. simus—or the “giant short-faced bear”—evolved from a population of A. pristinus bears in western North America.

While the two species had some overlap in their ranges, it appears that they mostly established territory that was separate from each other. A. pristinus (or the “lesser short-faced bear”) grew to roughly the size of a modern grizzly bear and was extinct by around 300,000 years ago.

The reasons for its disappearance aren’t known with certainty, but it has been theorized that a mixture of climate change and being outcompeted by other ursids led to their downfall.

The giant short-faced bear, on the other hand, was still thriving at this time and could be found throughout North America, but was most common in the western portions of the continent. Though they seemed to prefer temperate woodland, these bears were adaptable and able to survive in a variety of habitats.

North America’s Largest Bear

A. simus displayed a high degree of sexual dimorphism, meaning that there were noticeable morphological differences between males and females.

Female giant short-faced bears, on average, weighed about 1,100 lbs. By comparison, the males were much bigger—typically around 1,800 lbs—with the largest among them reaching a weight of more than 2,000 lbs.

They were approximately five feet tall at the shoulder and an astounding 11 feet tall when standing on their hind legs, making them the largest bears in North American history.

Amazingly, some of their relatives to the south were even larger. For example, Arctotherium angustidens, a South American short-faced bear, could grow as large as six to seven feet tall at the shoulder, as well as up to 14 feet tall when standing on its hind legs, and could weigh as much as 4,000 lbs.

The ancestors of A. angustidens are believed to have migrated to South America during the Great American Biotic Interchange—a significant period of migration in the Americas following the formation of a land bridge between North and South America.

Arctodus is a member of the Tremarctinae subfamily of bears, of which only one species survives—the spectacled bear of South America.

In 1878, the earliest fossils of the giant short-faced bear were discovered in the Potter Creek Cave in California.

The moniker “short-faced bear” was inspired by the belief that these animals had a disproportionately shorter snout and face than modern bears. This is now thought to be false and the apparent shortness was merely an illusion created by what was actually a combination of a deeper—but not shorter—snout, and short nasal bones.

Predator or Scavenger?

It was initially hypothesized that Arctodus simus was a predatory bear with a strictly carnivorous diet. However, a later examination of their bone collagen revealed the presence of both carbon-13 and nitrogen-15 isotopes, indicating that these bears consumed both meat and plant material.

Specifically, it appears that they browsed on vegetation as well as prey on herbivores, such as tapir, camelids, and deer. Additionally, bite marks believed to have been made by A. simus have been found on the fossils of juvenile mastodons and ground sloths.

So, in other words, they were omnivores like most modern bears.

But were they ever active predators? Or were they simply opportunistic scavengers? The structure of their limbs suggests that they were adapted more for long-distance walking, rather than the explosive bursts of movement and high-speed pursuits that one would expect from a predator.

Furthermore, their broad snouts hint at a well-developed olfactory system and a keen sense of smell—something that would have been invaluable for a scavenger.

Perhaps they led a lifestyle similar to that of their only living relative, the spectacled bear, who is primarily herbivorous but will occasionally hunt or scavenge animals.

Why Did They Vanish?

How—and why—did a bear that was seemingly highly adaptable, with a varied diet and an ability to survive in many habitats, go extinct? They vanished from the fossil record approximately 12,800 years ago.

And while there is some limited evidence that early humans like the Clovis peoples hunted them on occasion, nothing overtly indicates that they were hunted to excess.

However, the Late Pleistocene Epoch was when much of the world’s megafauna was vanishing, believed to be the result of a combination of climate change and overhunting.

One theory for why the giant short-faced bear was among the victims of this extinction event is that perhaps many of the plants and prey animals that made up its diet were dying out, making it impossible for it to survive as well. Still, the question remains and is a topic of debate.

Another thing to consider is the apparent lack of genetic diversity of this species. Mitochondrial DNA recovered and sequenced from specimens in Alberta, Ohio, Alaska, and the Yukon, revealed a very low level of genetic diversity. This could have potentially led to serious health problems and could, at least in part, be responsible for the bear’s downfall.

However, more research and data are needed to reach any definitive conclusions.

With each new discovery, this fascinating bear—one of the largest land animals of its time—continues to inspire discussion and debate.

Sources

North American Bear Center

University of Iowa Museum of Natural History

Yukon Beringia Interpretive Centre

The Revelator

Discover Magazine

Wikipedia

PBS Eons

(This article was originally published on Medium)

Origins of the Horse

When I was a child, my grandfather adored horses and owned a few of his own. My early experiences with them led to an enduring love of these gentle, sweet-eyed animals, and a fascination with their evolutionary history, which is more complex and diverse than one might think.

Though there is only one genus of horse remaining — Equus — there were many more in the past, each with an interesting story. Our understanding of prehistoric horses and their complicated family tree is ever-evolving as scientists discover more fossils.

This will be a brief history of horse evolution.

Dawn Horse

A small fossilized jaw discovered in the Thames River in 1838 puzzled Sir Richard Owen, a leading paleontologist of his time. He speculated that it might belong to a monkey or a pig. But he thought the teeth resembled that of a hyrax (a small mammal), leading him to name it Hyracotherium or “hyrax-like beast.”

A subsequent discovery would create further confusion. In 1876, paleontologist Othniel C. Marsh described a new genus, Eohippus, based on fossils found in New Mexico.

Decades later, in 1932, another paleontologist — Sir Clive Forster-Cooper — noted striking similarities between Eohippus and Hyracotherium, coming to the conclusion that they were one and the same.

As the rules of zoological nomenclature dictate that the earliest scientific name takes priority, Eohippus became Hyracotherium.

However, a later examination of the type specimen (in this case the jaw described by Owen) of Hyracotherium suggested that it was actually not a horse, but rather a member of a related group — known as palaeotheres — and that the fossils originally described as Eohippus represented a species from an entirely different family.

This revelation led to the name Eohippus being restored.

Eohippus — a beautiful Greek name meaning “dawn horse” — is the earliest known member of the family Equidae. A small forest-dwelling equid standing at just one foot tall, it had four-toed front feet and three-toed hind feet.

Many of their teeth resembled those of the various species of Equus. These animals lived in both North America (where they originated) and Europe, and evolved approximately 56 million years ago (Eocene Epoch).

Diversification Begins

Equid speciation soon occurred, with two distinct lineages evolving from Eohippus: Miohippus (“small horse”) and Mesohippus (“middle horse”).

Both appear to have been common in North America, with the former genus being particularly successful, having existed from approximately 32–25 million years ago, before vanishing from the fossil record after the Late Oligocene Epoch.

Mesohippus was the first member of the subfamily Anchitheriinae, a group of equids who would live and thrive in North America and Eurasia. Anchitheres, ancestors of a later genus — Sinohippus — had likely migrated to Asia via the Bering Land Bridge. Sinohippus would eventually find its way to Europe.

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Prehistoric Horses Grow Larger

Though many early horses were small animals, some grew to larger sizes. Megahippus, which lived in the southern United States during the middle Miocene Epoch (from around 15–11 million years ago), reached a weight of nearly 600 lbs. These equids were specialized leaf browsers, rather than grass grazers.

Many early species of horses ate leaves and berries, but as time went on, more and more of them began grazing instead.

Parahippus, another Miocene horse, could be found in Florida and the Great Plains region of the United States. It is believed that this genus represents the link between early forest-dwelling horses and the later grazers of the plains. It also had a longer, more traditionally horse-like head.

Equids in South America

Hippidion was a prehistoric horse known only from South America, where it lived from roughly 2.5 million years ago until its extinction 11,000 years ago (Pleistocene Epoch).

It has the distinction of being one of only two lineages of equids native to South America during the Pleistocene. Hippidion was on the smaller side and resembled a donkey.

The horse family tree was very diverse, with species varying in size and number of toes, with some living in forests, while others preferred grazing in the open plains; some remained in North America, while others chose to branch out and migrate to Asia and Europe or even back to North America.

The Evolution of Equus

Dinohippus is the equid from which Equus would eventually evolve. Interestingly, it was the first horse to possess the “stay apparatus” in its legs, which allows an animal to remain standing with little effort and to even enter a light sleep while upright.

In its time, it was a common animal and its fossils have been recovered from more than 30 sites. These horses existed from around 13–5 million years ago (Miocene).

The last common ancestor of horses, zebras, and donkeys likely lived approximately 4.5 million years ago.

The earliest known member of the modern horse family was Equus simplicidens — also known as the “Hagerman horse” after the site near Hagerman, Idaho, where many fossils of the species were found in 1928.

The Hagerman horse was comparable in size to a modern zebra, with a height of 43–57 inches and a weight of 660–880 lbs. They were found throughout much of the central and western portions of the U.S. and seemed to prefer grasslands and floodplains.

They vanished about 10,000 years ago. In fact, all horses in North America were extinct by this time. However, they were still living and thriving in Europe and Asia.

The reason for the disappearance of North America’s native horses is still a matter of debate, but scientists believe climate change and overhunting by humans to be the most plausible explanations.

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Reintroduction to North America

Horses remained absent on the continent until they were brought over from Europe by Spanish conquistador Hernán Cortés and his men in 1519, when they arrived in Mexico.

That wouldn’t be the last time Europeans brought horses over, and other 16th-century explorers, like Francisco Vázquez de Coronado and Hernando de Soto, were also accompanied by these animals.

Once in North America, they were obtained by various Native American tribes and became important animals to them as well.

Though Equus is the only living genus of horses, there are hundreds of breeds still around today.

Additionally, there are not only millions of domesticated horses but also more than 300,000 wild horses currently in the U.S.

The complexity of their history and family tree — which appears to have had many branches — is still not fully understood and new discoveries continue to add more layers to their story.

These beautiful animals are beloved by many and are considered a powerful American icon to this day.

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Sources

• Wild Horse Country: The History, Myth, and Future of the Mustang, America’s Horse by David Philipps

• Wikipedia

• NWF Blog

• Dinopedia

• Florida Museum

• Florida Museum

• “The Truth of Horse Evolution” — Ben G Thomas, YouTube

• PubMed

• American Museum of Natural History

• Wikipedia

• Wikipedia

(This article was originally published on Medium)

Barbary Lions

The Barbary lion, a member of Panthera leo leo, has inspired amazement in humans for thousands of years. Though part of an extant subspecies, it’s considered a distinct subgroup due to its unique morphology and behavior, and is now gone from the wild.

The memorable characteristics of the Barbary lion, as well as its elusiveness, granted it a near-mythical status, creating an intense fascination with the majestic animal that often did it more harm than good.

Lion Evolution

The modern lion’s ancestors first evolved approximately 56–59 million years ago, in the Paleocene Epoch. These mammals, such as Dormaalocyon, were quite small, weighing in at less than one pound and reaching a length of 8–10 inches.

The Felidae family evolved around 25 million years ago and eventually split off into two subfamilies: Pantherinae (lions, leopards, tigers, jaguars) and Felinae (lynx, bobcats, mountain lions, pumas, cheetahs, domestic cats).

The genus Panthera made its first appearance in the fossil record about 3.8 million years ago (Pliocene Epoch).

Panthera leo fossilis, an early lion, was more muscular and smaller than the modern lion, and lived in Eurasia approximately 1.5 million years ago.

One of the most iconic prehistoric big cats is the cave lion (Panthera spelaea), which lived across Eurasia and northwestern North America during the Pleistocene Epoch and was prominently featured in Paleolithic art.

Cave lions had some notable characteristics that differentiated them from their relatives, including that the males didn’t have a mane. It also appears that they didn’t interbreed with other lion species.

Approximately 500,000 years ago, the lineages of the cave lion and modern lion diverged.

Another close relative of African lions is the American lion (Panthera leo atrox). It lived in North America from roughly 340,000 years ago until its extinction 10,000 years ago. American lions were among the largest felids ever to exist, coming in at up to 8 feet long and 800lbs, according to some estimates.

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Barbary Lion History

Fossil evidence suggests that the Barbary lion evolved around 100,000 years ago in North Africa. These big cats inhabited the mountains, forests, and deserts of Egypt, Morocco, Tunisia, Libya, and Algeria.

The Barbary lion captured the imagination of Ancient Egyptians, appearing frequently in their artwork. In Egypt, the lion was considered symbolically significant, evoking power and guardianship, and was associated with Sekhmet, the lion-headed goddess of war and medicine.

Lion-headed amulets and figures dating back to the Iron Age have turned up during tomb excavations in places like the islands of Crete, Rhodes and Euboea.

Egyptian pharaohs were known to hunt Barbary lions and some, like Ramses II, are thought to have kept a few as pets.

The Nubian culture had a reverence for these lions and also regarded them as a powerful symbol, regularly representing them in their architecture and art.

Ancient Romans often used Barbary lions to fight gladiators in the Coliseum, and it’s estimated that thousands of the animals were killed during the reign of Caesar.

A combination of the rise of civilizations in North Africa and desertification is believed to have been largely responsible for causing lion populations to become more isolated in the region.

Barbary lions were also transported to Europe during the Middle Ages, where they were kept as popular attractions in places like the Tower of London’s menagerie. This was later proven when the DNA of two well-preserved skulls found at the Tower in 1936 and 1937 was tested. Radiocarbon dating of the skulls indicated that they came from around 1280–1385 and 1420–1480, respectively.

Additionally, lions had been gifted to the royal family of Morocco. However, when the family was exiled in 1953, these 21 big cats were transferred to two different zoos. A later analysis of mitochondrial DNA from a lion that had come from this collection would reveal that it was likely a descendant of the Barbary lion.

By the 19th century, Barbary lions were common attractions in circus menageries and hotels.

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Behavior and Morphology

Barbary lions are regarded as a unique population among the Panthera leo leo subspecies, due to their distinct morphology and behavior. For example, the male generally had a thick and very dark mane that extended to his belly, as well as over his shoulders. The extra insulation was likely because they were adapted to live and thrive in the cooler parts of Africa, including the Atlas Mountains in the wintertime.

The manes of male zoological specimens range in color from light to dark tawny. Among these specimens, the males varied in size from 7.9 feet to 9.2 feet long, while the females averaged 8.2 feet in length.

Interestingly, a 20th century study conducted on lions in the Serengeti National Park showed that factors such as nutrition, ambient temperature and testosterone levels influence the color and size of the mane.

Historical accounts from hunters asserted that Barbary lions were the largest of all lions they encountered, claiming that they reached a size of up to 660 lbs and 10 feet long.

However, captive Barbary lions are known to have been smaller, at least in weight. But it’s unclear if this was an accurate reflection of their true size potential, as they were historically kept in poor conditions and probably malnourished.

Even before the animals became scarce in the wild, they were notably solitary by lion standards and were commonly observed either on their own or in small prides consisting of a male, female, and one or two cubs.

Other predators within their range included the Atlas bear and African leopard.

The Barbary lion’s diet consisted of animals like gazelles, red deer, oryx, wild boar, and, eventually, livestock.

Disappearance in the Wild

Their numbers dramatically decreased when firearms and lion bounties became more widespread across their range, and they were possibly already extirpated throughout much of the Mediterranean coast region by the 1830s.

The last photograph of a wild Barbary lion—a haunting aerial shot taken by Marcelin Flandrin in 1925—shows one wandering alone in the Atlas Mountains.

The last recorded shooting of one of these animals occurred in Morocco in 1942, and the final sighting of a wild Barbary lion that is regarded as legitimate took place in Algeria in 1956.

However, a study—which examined statistical data like sighting records and the average lifespan of these lions—estimated that Barbary lions might have existed in the wild until as late as the mid-1960s.

Are They Still Around?

It was a long-held belief that the Barbary lion was a unique subspecies of African lion. That is, until the findings of a genetic study were published in 2016, which revealed that they actually belong to the extant subspecies Panthera leo leo and are part of the same subclade as the Asiatic lion.

But, as previously mentioned, the Barbary lion is considered to be a distinct subgroup of P. l. leo that is extinct in the wild.

Yet while it’s no longer possible to encounter one in the wild, Barbary lions are not gone entirely and it’s estimated that there are still as many as 80–100 of these majestic animals in zoos across Europe and Morocco today.

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Additional Sources

• IFLSCIENCE

• G’s Data Lab, YouTube

• NSU Florida

• National Geographic

• Wikipedia

• Wild Ciencias, YouTube

• ThoughtCo

• Animalogic, YouTube

(This article was originally published on Owlcation)