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New World porcupines originated in South America and dispersed into North America between 4 and 3 million years ago. Prehensile-tailed porcupines today live in tropical forests of Central and South America. In contrast, North American porcupines (Erethizon dorsatum) are thought to be adapted to higher-latitude temperate forests, with a larger body, shorter tail, and diet that includes bark. In a paper published this week in the journal Current Biology, paleontologists described functionally important features of the skeleton of the extinct porcupine Erethizon poyeri, the oldest nearly complete porcupine skeleton documented from North America, found in the Early Pleistocene of Florida.
North American porcupines differ from the southern relatives in having more fur, a shorter tail and a bulkier frame.
Porcupines are a type of rodent, and their ancestors likely originated in Africa more than 30 million years ago.
Their descendants have since wandered into Asia and parts of Europe by land, but their journey to South America is a particularly defining event in the history of mammals.
They crossed the Atlantic Ocean — likely by rafting — when Africa and South America were much closer together than they are today.
They were the first rodents to ever set foot on the continent, where they evolved into well-known groups like guinea pigs, chinchillas, capybaras and porcupines.
Some took on giant proportions. There were lumbering, rat-like animals up to five feet long, equipped with a tiny brain that weighed less than a plum. Extinct relatives of the capybara grew to the size of cows.
Porcupines remained relatively small and evolved adaptations for life in the treetops of South America’s lush rainforests.
Today, they travel through the canopy with the aid of long fingers capped with blunt, sickle-shaped claws perfectly angled for gripping branches.
Many also have long, prehensile tails capable of bearing their weight, which they use while climbing and reaching for fruit.
Despite their excellent track record of getting around, South America was a dead end for many millions of years.
A vast seaway with swift currents separated North and South America, and most animals were unable to cross — with a few notable exceptions.
Beginning about 5 million years ago, the Isthmus of Panama rose above sea level, cutting off the Pacific from the Atlantic.
This land bridge became the ancient equivalent of a congested highway a few million years later, with traffic flowing in both directions.
Prehistoric elephants, saber-toothed cats, jaguars, llamas, peccaries, deer, skunks and bears streamed from North America to South.
The reverse trek was made by four different kinds of ground sloths, oversized armadillos, terror birds, capybaras and even a marsupial.
The two groups met with radically different fates. Those mammals migrating south did fairly well; many became successfully established in their new tropical environments and survived to the present. But nearly all lineages that ventured north into colder environments have gone extinct. Today, there are only three survivors: the nine-banded armadillo, the Virginia opossum and the North American porcupine.
South American porcupines are equipped with a menacing coat of hollow, overlapping quills, which offer a substantial amount of protection but do little to regulate body temperature.
North American porcupines replaced these with a mix of insulating fur and long, needle-like quills that can be raised when they feel threatened. They also had to modify their diet, which changed the shape of their jaw.
“In winter, when their favorite foods are not around, they will bite into tree bark to get at the softer tissue underneath. It’s not great food, but it’s better than nothing,” said Natasha Vitek, a reseracher at the Florida Museum of Natural History.
“We think this type of feeding selected for a particular jaw structure that makes them better at grinding.”
“They also lost their prehensile tails. Although North American porcupines still like climbing, it’s not their forte.”
“Museum specimens often show evidence of healed bone fractures, likely caused by falling from trees.”
In the new research, Vitek and her colleagues examined an exquisitely preserved skeleton of an extinct porcupine species from Florida, the United States.
“It is so rare to get fossil skeletons like this with not only a skull and jaws, but many associated bones from the rest of the body,” said Dr. Jonathan Bloch, vertebrate paleontology curator at the Florida Museum of Natural History.
“It allows for a much more complete picture of how this extinct mammal would have interacted with its environment.”
“Right away we noticed that it was different from modern North American porcupines in having a specialized tail for grasping branches.”
By comparing the fossil skeleton with bones from modern porcupines, the researchers were confident they could determine its identity.
“The results were surprising. The fossil lacked the reinforced bark-gnawing jaws and possessed a prehensile tail, making it appear more closely related to South American porcupines,” Vitek said.
“But other traits bore a stronger similarity to North American porcupines, including the shape of the middle ear bone as well as the shapes of the lower front and back teeth.”
With all the data combined, analyses consistently provided the same answer.
The fossils belonged to Erethizon poyeri, an extinct species of North American porcupine, meaning this group has a long history that likely began before the Isthmus of Panama had formed.
But questions remain as to how many species once existed in this group or why they went extinct.
“One thing that isn’t resolved by our study is whether these extinct species are direct ancestors of the North American porcupine that is alive today,” Vitek said.
“It’s also possible porcupines got into temperate regions twice, once along the Gulf Coast and once out west. We’re not there yet.”
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Natasha S. Vitek et al. An extinct North American porcupine with a South American tail. Current Biology, published online May 27, 2024; doi: 10.1016/j.cub.2024.04.069
