A surprising discovery has emerged from dusty museum closets. Closer inspection of around 800 long-dead reptiles reveals that the Caribbean has a whopping 39 species of skink — zippy little lizards — rather than six. Not since the 1800s have so many unique reptiles been added to a list of species in a single go, researchers say.

Joseph Burgess, courtesy of Pennsylvania State University

“I was stunned,” said Blair Hedges, an evolutionary biologist at Penn State and a co-author of a study on the skinks, published this week in the journal Zootaxa. “They were hiding in museum collections for more than a century.”

What started as an honors thesis by Caitlin Conn, an undergraduate for whom Dr. Hedges was an adviser, soon led to more complex and intriguing research on skink diversity. After sending out a few samples for genetic analysis of what they thought was one lizard species, the two were perplexed to find that the genetic readings did not match.

Seeking clarification, they began combing through museum collections around the world in search of preserved skink specimens that in some cases dated as far back as the 1780s.



It soon became obvious that a new classification system was in order. As with Darwin’s finches, it seemed that similar animals had diversified to fill different ecological niches, with some lizards growing larger or smaller and some climbing trees while others burrowed under logs.

A skink from St. Croix was six times the size of a similar skink from Anegada, for example, yet both animals were classified as belonging to the same species. “That kind of difference was really startling to me,” Dr. Hedges said. So he and Ms. Conn began the painstaking process of taxonomically classifying the species through scale counts and scale shapes, color patterns, size and genetic analysis.

What emerged were 24 brand new species and 9 species that were previously named by others but had until now been considered invalid, or 33 additions to the Caribbean lizard fauna over all. The team named most of the species after their respective islands or countries, like M. hispaniolae and S. haitiae, and described the results in a 244-page skink opus in Zootaxa.

Yet the celebration was muted by a realization that all of the new species qualify as vulnerable, threatened or critically endangered — and that at least 16 of them are probably already extinct. Those 16 have not been spotted in over 100 years, and in some cases only a single specimen exists to prove that the species ever scuttled about on the earth.

The bane, they found, was the mongoose. In 1872, humans introduced Indian mongooses to the islands with the intention of controlling rats. As so often happens when an alien species drops into a new environment, there were unforeseen consequences: the mongooses ran amok and began gobbling up all of the skinks.

The dates of Dr. Hedges’s specimens and, more telling, the dates after which the lizards ceased to be collected, correspond almost exactly with the introduction of the mongoose. Ongoing deforestation across the Caribbean also does not help the skinks’ survival prospects, he added.

Based on what he has learned, Dr. Hedges said he was “absolutely certain” that more than 16 species were lost to the hungry mongooses. We may never know about these other “ghost fauna” that possibly slipped through the 19th-century amateur collector’s grasp and then went extinct.

“If I had to guess, I’d say there were probably 6 to 12 additional species that were there that we’ll never know about,” Dr. Hedges said.

He suggests that the discovery highlights the importance of species classification to wildlife conservation. Under the previous taxonomy recognizing only six species, it appeared that wide-ranging skinks were not threatened since they lived on nearly all the islands.

In essence, the 16 vanished skink species were kept off the conservation radar because of a taxonomic oversight. “If we had known about them 50 years ago, we might have been able to save some of those species,” Dr. Hedges said. “They needed help, and we just weren’t there to help them.”

He remains hopeful that some of the missing species could be hiding out under logs or in trees on small, unexplored and mongoose-free Caribbean islets. One species in Puerto Rico, for example, was just taken off the “possibly extinct” list after being spotted by an amateur photographer.

“I’m crossing my fingers that some species that haven’t been seen in 100 years may still be on these little islets,” Dr. Hedges said. “When I get a chance, I’m going to go look there.”