New World porcupines originated in South America and dispersed into North America between 4 and 3 million years ago. Today, prehensile tail porcupines live in the tropical forests of Central and South America. In contrast, North American porcupine (Erethizon Dorsatum) It is thought to be adapted to temperate forests at higher latitudes, with a larger body, shorter tail, and a diet that includes bark. paper Published in this week's journal Current BiologyPalaeontologists have described functionally important features of the skeleton of an extinct porcupine. Erethizon PoeriThe oldest nearly complete porcupine skeleton recorded in North America, discovered in Florida from the Early Pleistocene.

Porcupines are a type of rodent whose ancestors probably originated in Africa more than 30 million years ago.

Their descendants subsequently migrated overland to parts of Asia and Europe, but the journey to South America is a particularly defining event in mammalian history.

They probably crossed the Atlantic Ocean on rafts at a time when Africa and South America were much closer than they are today.

They were the first rodents to set foot on the continent, where they evolved into familiar groups such as guinea pigs, chinchillas, capybaras, and porcupines.

Some were gigantic – lumbering, mouse-like creatures up to five feet long, with tiny brains and weighing less than a plum – and a close relative of the extinct capybara that grew to the size of a cow.

Porcupines have evolved to remain relatively small and adapt to life in the trees of the lush tropical rainforests of South America.

Now they move through the tree canopy using long fingers with blunt, sickle-shaped claws perfectly angled to grip branches.

Many birds have long, prehensile tails that can support their body weight and help them climb trees and pick fruit.

Despite its impressive track record of migration, South America was a dead end for millions of years.

North and South America are separated by a vast ocean passage with rapids, which most animals could not cross, with a few notable exceptions.

Beginning about 5 million years ago, the Isthmus of Panama rose above sea level, separating the Pacific and Atlantic oceans.

Millions of years later, this land bridge would become the equivalent of an ancient, congested highway, allowing traffic to flow in both directions.

Prehistoric elephants, sabre-toothed tigers, jaguars, llamas, peccaries, deer, skunks and bears migrated from North America to South America.

Also joining us on the reverse journey were four species of ground sloths, an oversized armadillo, fearsome birds, capybaras and even marsupials.

The two groups had radically different fates. The mammals that migrated south did relatively well, and many successfully colonized their new tropical environments and have survived to the present day. But the lineages that moved north into colder environments almost entirely went extinct. Only three species remain today: the giant armadillo, the Virginia opossum, and the North American porcupine.

South American porcupines have a formidable coat of hollow, overlapping quills that provide considerable defense but little in the way of thermoregulation.

North American porcupines replaced this with a mixture of insulating hairs and long, needle-like hairs that they erect when they sense danger. They also had to change their diet, which led to a change in the shape of their jaws.

“When their favorite foods disappear in the winter, they'll nibble at tree bark and eat the soft tissue underneath. It's not the tastiest food, but it’s better than nothing,” says Natasha Vitek, a research scientist at the Florida Museum of Natural History.

“This type of feeding appears to have been selected for a particular jaw structure that enhances the ability to grind teeth.”

“They also lost their tails, which they used to prehensile. North American porcupines still love climbing trees, but it’s not their forte.”

“Museum specimens often show signs of healed fractures, likely caused by falls from trees.”

In the new study, Vitek and his colleagues examined an exceptionally well-preserved skeleton of an extinct species of porcupine from Florida, US.

“It's very unusual to find a fossil skeleton like this, which includes not only the skull and jaw, but also many other bones from other parts of the body,” said Dr. Jonathan Block, curator of vertebrate paleontology at the Florida Museum of Natural History.

“This will give us a more complete picture of how extinct mammals interacted with their environment.”

“We quickly realized that it was different from modern North American porcupines in that it had a specialized tail for grasping branches.”

The researchers were confident that by comparing the fossil skeleton with modern porcupine bones they could pinpoint its identity.

“The results were surprising: the fossil lacked the reinforced jaws for gnawing at bark, but had a tail adapted for prehensile functions, making it more similar to South American porcupines,” Vitek said.

“But other features, such as the shape of the middle ear bones and the shape of the lower front and back teeth, bore stronger similarities to North American porcupines.”

When all the data was combined, the analyses consistently gave the same answer.

Fossils Erethizon Poeriis an extinct species of North American porcupine, and this group has a long history that likely began before the formation of the Isthmus of Panama.

But questions remain about how many species in this group once existed and why they became extinct.

“One of the things our study leaves unresolved is whether these extinct species were the direct ancestors of today’s living North American porcupines,” Vitek said.

“It’s possible that porcupines have invaded temperate zones twice — once along the Gulf Coast and once in the West — but we’re not there yet.”

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Natasha S. Vitek othersAn extinct North American porcupine with a South American tail. Current BiologyPublished online May 27, 2024; doi: 10.1016/j.cub.2024.04.069