A new species of armadillo was hidden from view

They are scaled, covered in armor, and hide a secret identity. Nine-banded armadillos (Dasypus novemcinctus), the idiosyncratic mammal that ranges from southern Illinois to northern Argentina, are not in fact one species. Instead, the group of these unusual animals consists of four different species, according to a study published in the journal in June Systematic biology.

Armadillos belong to Xenarthra, the mammal group native to the Americas that also includes anteaters and sloths. Although armadillos are a classic symbol of the American South, particularly Texas, where they’re a beloved mascot for everything from sports teams to restaurant chains, they’re actually relatively recent arrivals. The armored beasts first took up residence north of the Rio Grande in the late 1800s, having crossed the river on their own. Around the same time, the reptilian mammals were introduced to Florida by humans. They’ve continued to spread ever since. In recent years, individual armadillos have been spotted as far north as Illinois and Indiana and as far east as Virginia. Why and how they’ve managed to spread so widely remains a mystery, but now we’re learning more about the different species of these curious creatures.

Through genetic and trait analysis, biologists say they have uncovered the secret variety hiding under the umbrella of the oversimplified armadillo clade. Previously, there were 21 recognized species of armadillos, and so splitting one lineage into four represents an approximately 14% increase in dillo diversity. In addition to broadening the armadillo family tree, the new classifications could have significant conservation implications as scientists consider the four species in a new context.

Two of the newly defined species had been proposed as subspecies in previous research. One of the species retains the name and description of the classic nine-banded armadillo. The fourth represents a previously undescribed species (the first within armadillos in 30 years).

The news means that the state animal of Texas is getting a new name: it’s now called the Mexican long-nosed armadillo (Dasypus mexicanus), which covers the northernmost part of the nine-banded armadillo’s former range – from Costa Rica to the US. And then there is Dasypus fenestratus living in the western Andes, from Costa Rica through Ecuador, Northern Colombia and Northern Venezuela. Only the southernmost part of the former nine-banded armadillo, which includes most of South America, is still the official home of the nine-banded armadillo.

Finally, there is the Guyana long-nosed armadillo (Dasypus guianensis). This previously undescribed species inhabits the Guinea Shield, a 1.7 billion-year-old geological formation that encompasses several high-altitude areas underlying Guyana, Suriname, French Guiana and part of Venezuela.

“Every species now has a much more limited distribution,” said Anderson Feijó, a co-author of the study and assistant curator of mammals at the Field Museum of Natural History in Chicago. “This finding changes the way we think about the ecological needs of these animals,” he added. What was previously considered an animal with broad adaptability and a large range, not at risk of losing territory, will now have to be re-examined four times. It’s possible that each species has different habitat needs or resources, and in some places those aren’t being met.

“We will now have to reassess each of the four different entities,” said Frédéric Delsuc, senior author of the study and evolutionary biologist at the French National Center for Scientific Research. Delsuc is also part of the specialist group at the International Union for Conservation of Nature (IUCN) responsible for classifying where armadillo species should be included on the IUCN Red List. He’s eager to evaluate each of the four newly delineated species, though he’s not immediately concerned about any of them given how often they’re spotted on highways, he says, indicating they’re likely “quite plentiful.”

While sad for armadillos, the mammals’ tendency to get run over by cars was actually a boon for the researchers. Just over half of their 80 armadillo samples came from dried specimens, mostly museum specimens. But 34 samples were collected fresh in the field, “mostly from roadkill,” Delsuc says.

Using these armadillo pieces from across the former nine-band area, the scientists extracted both mitochondrial and nuclear DNA. They conducted multiple analyzes to dissect the exact relationships between their 80 test animals. In one type of analysis, they repeatedly grouped the individuals based on genetic similarity, and found that four clusters emerged again and again. In another type of analysis, they assessed gene flow between these clusters. Although they found some evidence of hybridization, these cases were rare and only observed at the margins of each group’s range. “All this supports these four lineages as separate species,” says Mathilde Barthe, the study’s lead author who recently completed her PhD in molecular evolution at the University of Montpellier in France.

It’s unclear how long ago the various branches of the armadillo split off, but the presence of low levels of hybridization suggests this was likely relatively recent, on the scale of evolutionary time, Delsuc notes.

A thorough genetic analysis was key to discovering and defining the species split, because all four species are largely visually similar. At first glance or in the field, “it’s very difficult to tell them apart,” Feijó says. But there are subtle differences in skull shape that allow experts to distinguish between skeletal specimens, Delsuc says. And the new Guyana species is the most distinct from the others. It’s slightly larger, has a hairless shell, an extra vertebrate and a domed, thick skull, according to Feijó’s formal description. Additional research could reveal that the species diverge in other ways, such as behavior or diet.

The new findings have been 25 years in the making and build on previous studies of armadillo diversity. There are still some limitations, however. The DNA in museum specimens is often contaminated and degraded. The scientists took “special care” to reduce the impact of that potential contamination and filter their data, Barthe says, but some oddities may have slipped through the cracks. Still, none of the researchers expect their proposal to cause much controversy. “The evidence has been piling up and has led to this final conclusion,” Feijó says.

There is still so much to learn, even about mammal biology. “People usually assume that mammals are a very well-known group,” says Feijó. “But the reality is we are just learning.” Today there are four newly defined species. Tomorrow, he notes, there will likely be more.