Six new species of western U.S. rattlesnakes have just been identified, according to a paper released this week.

Animal experts previously puzzled over the newly named rattlers, but did not then realize that the snakes represented unique species.

First Snake Crawled on Four Feet: Photos

“These snakes have been long been recognized by herpetologists as being demonstrably different, and in fact were designated as western rattlesnake subspecies in the first half of the 20th century,” co-author Michael Douglas, a professor of biological sciences at the University of Arkansas, said in a press release.

He and co-author Marlis Douglas collaborated with Mark Davis, a research scientist at the Illinois Natural History Survey, and with Michael Collyer of Western Kentucky University. Their findings are published in the journal PLOS ONE.

As part of his doctoral research, Davis had previously collected data from nearly 3,000 western rattlesnakes available in natural history museums across the western U.S.

Video: Why Is Everyone Afraid Of Snakes?

Analysis of the snakes’ DNA and head shapes enabled the researchers to identify the different rattlesnakes. The six new ones are as follows:

  • Crotalus viridis

  • Crotalus oreganus

  • Crotalus cerberus

  • Crotalus helleri

  • Crotalus concolor

  • Crotalus lutosus

“Crotalus” comes from the Greek word krotalon, which means “rattle” or “castanet.” All such snakes are venomous pit vipers.

Rattlesnake Colony Planned for Uninhabited Island

Often when new species are discovered, they are declared to be highly endangered, helping to explain why they were not found earlier. That does not seem to be the case in this instance, though.

Michael Douglas said of the rattlesnakes, “None are currently considered rare, but species designation allows them to gain certain legal protection, particularly within individual states.”

The newly identified rattlesnakes are expected to go into the animal record book after their scientific and standard English names are submitted to the International Commission on Zoological Nomenclature.